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PostPosted: Wed Jul 23, 2008 4:44 am 
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Retired Gearhead
Retired Gearhead
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Joined: Mon May 19, 2008 12:35 pm
Posts: 3989
Location: Ames, Iowa
Year and Trim: 98 Caravan is the daily driver 215K
Change Upper Intake Manifold (UIM) and Lower Intake Manifold (LIM) gaskets

Disclaimer: Performing repairs on automobiles can result in damage to property, personal injury, or death. The author is not responsible for any losses incurred as a result of the use of this information. Persons using this information do so at their own risk.

This procedure was written based on repairs made to a 1997 non-supercharged (L36) engine. Other years are similar, but will not be exactly the same. The cost (March, 2009) for the parts and supplies needed to perform the work described herein is between $230 - $300 depending upon the sources of supplies, and the number of oil changes.

For supercharged engines (L67), the supercharger assembly takes the place of the plastic UIM used on the L36. Torque specifications for the supercharger assembly differ from the plastic intake used on the L36. Different seals, LIM, and other parts are also used for supercharged engines. However, once the supercharger and its related components are removed, the work involved to change the LIM gaskets is essentially the same as for the L36.

While an experienced mechanic may be able to perform this work in less than one working day, the first time out, it will be better to plan for a couple of days to get all of the work described done carefully and correctly. Some of the tools you will need:

Good set of socket wrenches in 3/8" and 1/4" drive
5/16" and 3/8" six-point sockets
Universal (swivel) adapter and a selection of extensions
Torque wrench capable of accurately measuring inch pounds or 7.5 ft-lbs
Snap ring pliers for MAF screen
Torx security socket for MAF sensor
Feeler gauges and straight-edge for measuring flatness of LIM & heads
Pliers and screwdrivers
Vise-grips
A good gasket scraper, preferably with a heavy, carbide blade
Vacuum cleaner
Hand vacuum pump or wet-vac
Small ball-peen hammer
Old toothbrush, parts cleaning brush, wire brushes, cleaning pan

Read this entire article before beginning to work. Work safely. Removing injectors from the fuel rail will result in gasoline spillage and gasoline vapors. Keep spark and flame well away. Use jack stands when working under the vehicle. Do not get under a vehicle supported only by a jack. Note: for convenience, fasteners are referenced by bolt head and nut sizes, not bolt diameter. For torque specifications not mentioned in the text, please consult: Techinfo torque specs

General Hints

O-rings: O-rings can be damaged by attempting to remove or install them against dry surfaces. A squirt of penetrating oil will greatly ease the removal or installation of o-rings. Depending on where they are used, anti-freeze, oil, or silicone grease can also be used as a lubricant.

Mark parts for re-installation: Buy two Sharpie marking pens - silver for dark surfaces, and black for light surfaces. Use them to number spark plug wires, show which end of a bracket goes up, etc. Brake parts cleaner will remove the markings when you've got it back together, if you prefer an unmarked engine. Use plastic baggies and a marker to label fasteners so they go back where they were. Where practical, start fasteners back on the part where they belong. Take a photograph of complicated assemblies before taking them apart. Refer to the image when re-assembling.

Clean fasteners: Clean bolt threads of oil, grease and sealant with solvent and a wire brush. Generally, threads should be clean and lightly lubricated. Threads and bolt holes must be clean and dry for thread locker to adhere. Threads must be lightly lubricated to obtain accurate torque measurements. (Thread locker will work as the lube for the UIM and LIM bolts.)

Parts cleaning: A gallon of kerosene or mineral spirits, a plastic pan and a stiff parts cleaning brush can do the job inexpensively. Work in a well ventilated area when using throttle body cleaner or brake parts cleaner.

Rusty fasteners: Wire brush any rust on threads that you can reach. Good penetrating oils are very effective when given time to work. PB (power blaster), SeaFoam Deep Creep, and Kroil are good penetrating oils for rusty fasteners. WD-40 is not nearly as effective. Tapping on the fastener with a small hammer after applying the product encourages penetration. Arrange your work so that you provide at least 15 minutes for the penetrant to do its job. Applying penetrant the night before is even better. Very tight bolts sometimes can be freed by tightening a little bit, then loosening, applying penetrant and repeating, moving a little farther each time.

Cover openings: It is a good idea to cover the crankcase and plug the ports on the cylinder heads and LIM to prevent dirt, debris, fasteners or tools from falling into the engine when you are working on it. You can use rags, or stuff panty hose into the holes. If scrapings or dirt fall into an open port, use a vacuum cleaner to remove them.
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If you are performing this work because your LIM gaskets or UIM have failed, rather than as preventive maintenance, you will need to perform the following preliminary tasks to minimize the risk of premature bearing failure in your engine.

Drain the coolant. Drain the oil. Change the oil filter. Pull all six spark plugs. Rotate the engine through several revolutions by hand with a wrench on the crankshaft bolt. This will safely expel large quantities of coolant that might have entered any of the cylinders. Replace the oil drain plug and refill the crankcase with thin, cheap oil like 5W-30. Unbolt and pull out the connector to the ignition control module (ICM). Crank the engine for several ten second periods, allowing the starter to cool for a minute between each period. This is done to circulate fresh oil to the bearings and to flush residual coolant into the pan. Pull the drain plug and drain the oil.

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Parts and supplies Aluminum lower intake manifold gasket kit, APN upper intake manifold kit, blue threadlocker, rtv silicone gasket maker, parts cleaning solvent, high-temperature anti-seize compound, penetrating oil, rags, brake parts cleaner, rubbing alcohol, Q-tips, throttle body cleaner, silicone grease, nitrile gloves, two gallons of coolant, oil and oil filter(s), package of Dorman Help! coolant elbows from your local auto parts store. For 95-98 models, a new o-ring for the tensioner assembly to the water pump. This is listed as a tensioner seal at the GM dealer.

APN kit contents The APN kit contains a new upper intake manifold with a steel sleeve installed in the EGR stovepipe passage to act as a heat shield. It contains two stovepipes about 1/2" in outside diameter - one with a 3/4" shoulder to fit into the LIM of engines produced between 1995- 1998; and one with a 5/8" shoulder to fit engines produced from 1999 on. Also included is a new vacuum fitting for the accessory vacuum line and brake booster, a new PCV valve chamber cap for cars equipped with newer MAP sensors, a throttle body gasket, a new PCV tube, a new UIM gasket, and a set of o-rings and sleeves for the fuel injectors.

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Turn off Electronic Climate Control Gearhead Stan reminds you that before you disconnect the battery, it is a good idea to turn the Climate Control off, with the ignition key in the on position. This will minimize the potential for damage to the airmix door actuator that can occur if you don't.

Disconnect battery With a six-point 5/16" box wrench or socket, remove the negative battery cable from its terminal and tuck the cable end down so that it cannot touch the negative battery terminal.

Remove splash shield Slide under the front of the car and remove the plastic splash shield by undoing the 10mm bolts in the rear and sides and the 8mm bolts in the front.

Drain coolant Undo the spring clamp with pliers or the gear clamp (usually a 5/16" socket) securing the lower radiator hose to the radiator. Place a pan under, and wiggle the end of the hose partly off the nipple to drain the radiator and part of the coolant from the engine. Remove the radiator cap to provide a vent. For 2000 and newer, it may be easier to open the radiator drain cock. If you have compressed air available, you could use it to help remove residual coolant from the lower intake manifold like Jake (01bonneSC) did. Remove either end of the lower radiator hose over a drain pan, remove the upper radiator hose fitting from the LIM, then pull out the thermostat. Make a loose seal with a rag around a blow nozzle and apply air at the thermostat opening. This will push coolant from the lower intake manifold out through the water pump. Do not make the seal too tight or let the air pressure build up greater than 15 psi - too much pressure could damage the heater core.

Remove engine cover Remove the engine cover by twisting the oil filler neck counter-clockwise and lifting it out. Then lift the front of the cover to free the rear cup from the holder. Slide the cover forward and lift it off. Replace the filler neck and cap.

Remove air intake Remove the two small screws (6mm or 7mm) holding the front of the air box to the radiator cross brace. Unplug the IAT (intake air temperature) electrical connector. Peel the rubber collar of the flexible air duct back away from the throttle body. It helps if the rubber is warm - if working in the winter, heat the rubber with a hair dryer or heat gun. Lift out the air box and rubber duct.

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Prepare to remove crossover pipe Removal of the exhaust crossover pipe is optional. Beware! Attempting to remove a crossover pipe with very badly rusted bolts can result in the bolts breaking requiring significant additional work to replace them. If the crossover is not removed, extra effort is required in undoing the throttle body bracket, but not as much as repairing a broken exhaust bolt. I prefer to remove the crossover because it makes working with the throttle body and corrugated EGR (exhaust gas recirculation) tube easier and only takes a few minutes when you allow a good penetrating oil time to do its job. Spray the threads of the bolts holding the front of the crossover pipe to the front exhaust manifold with a good penetrating oil like PB or SeaFoam Deep Creep or Kroil. Do not use WD-40. Spray the nuts holding the heat shield on the studs securing the rear of the crossover pipe.

Mark wires Mark the spark plug wires at the coil connectors and remove them from the coil posts. Detach the wires from the UIM and otherwise as needed to place them out of the way in the front and back of the engine.

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Remove MAP sensor If so equipped, unclip the electrical connector for the MAP (manifold absolute pressure) sensor on the passenger end of the UIM. Depress the clips and gently pry the MAP sensor up and out of the hole in the cap of the PCV (positive crankcase ventilation) valve chamber. Pulling on the MAP sensor may cause it to break if it is stuck tightly in the hole. They cost $60.

Remove belt from alternator Check to make sure you have a belt routing diagram. If you do not, look at the accessory belt and draw one up for reference. With a 15mm socket and a long handle, turn the bolt on the tensioner assembly idler pulley counter-clockwise to loosen the accessory belt. Using only your hands, pull the belt off of the alternator pulley. It is not necessary to remove the belt from the lower pulleys.

Remove alternator Squeeze and wiggle the round plastic cover on the rear of the alternator. Lift it off to expose the output connection. Undo the 13mm nut and remove the output wire. Replace the nut on the bolt and replace the cover over the nut. Undo the 10mm bolt holding the top brace to the rear of the alternator (closest to the UIM). Undo the 10mm bolt holding the other end of the top brace. Note that the top brace is installed on top of the wiring harness. Now break loose (but do not remove) the two 10mm bolts holding the lower brace for the rear of the alternator to the alternator support bracket. You may have to wiggle the 10mm socket down between the wiring harness and the vacuum hose to the power brake booster. In the front of the alternator, remove the 13mm nuts securing the ends of the bracket between the alternator and under the coil packs (ICM). Remove the bracket. Now remove the two 13mm bolts and one 13mm stud securing the front of the alternator. Remove the two bolts previously loosened to remove the lower rear brace for the alternator. The alternator can now be lifted up and tilted to expose the electrical connector on the back for the voltage regulator. Undo the electrical connector for the voltage regulator and remove the alternator.

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Remove fuel rail with fuel lines Remove the electrical connectors for the fuel injectors by pressing the wire inward and pulling up on the connector. Some newer engines use a connector that is removed by lifting a blue plastic lock, then depressing a tab while wiggling the connector up and off. Relieve the pressure in the fuel rail by unscrewing the valve cap near the fuel pressure regulator. Cover the fitting with a shop rag to catch the gasoline that will squirt out under pressure when you push down the valve with a small screwdriver. It is not necessary to disconnect the fuel lines from the fuel rail. The rail and lines can be swung up out of the way near the rear of the engine. Remove the four 10mm nuts holding the fuel rail to the LIM. If compressed air is available, blow any dirt and grit away from the holes for the injectors. Squirt a little lubricant around the injectors where they enter the LIM. Wiggle each side of the fuel rail upward until the injectors are out of the bores. Pulling the wiring harness and any vacuum lines out of the way, lift the fuel rails up and turn them upside down near the rear of the hood. Wire or cable tie them up to the passenger windshield wiper.

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Begin removing crossover Now that the penetrating oil has had 15 minutes to work, undo the front bolts and the rear nuts on the exhaust crossover pipe with a 13mm six-point socket. Be careful that you do not apply too much force trying to break the bolts and nuts loose. If it seems the fasteners are so tight that they may break, it is better to leave the crossover pipe in place. Remove the heat shield from the rear and squirt the threads on the rear studs that enter the rear exhaust manifold with penetrating oil.

Remove EGR heat shield Undo the electrical connector for the EGR valve. Undo the 10mm nut and the 10mm bolt securing the heat shield for the EGR valve. Pinch the plastic nose of the wiring harness clip with pliers and push it back through the hole in the shield to remove the shield from the wiring harness.

Remove and clean sensors At the throttle body, undo the electrical connectors for the MAF (mass air flow sensor), TPS (throttle position sensor), and IAC (idle air control) valve. MAF: Using a small security torx tool, remove the two screws for the MAF and carefully twist and lift it out of its hole. Gently clean the wires with rubbing alcohol and a Q-tip, or spray with special MAF cleaner. Set it aside where you will not step on it. It costs $150.

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IAC: Using a screwdriver blade that fully fits the slot, remove the two screws securing the IAC. You may need to use a little penetrating oil as you go if the screws were secured with thread locker. Take your time. You do not want to break one of these off in the aluminum throttle body. Clean the pintle and spring of the IAC with a safe solvent like brake cleaner or throttle body cleaner. Do not push the pintle in. It is attached to a stepping motor. Do not spray cleaner up the spring toward the motor.

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Using a pair of snap ring pliers, remove the flat retainer holding the MAF screen in place. Be careful working around the honeycomb screen, it is easily damaged. Remove the vacuum lines (tee on top, straight fitting below) from the front of the throttle body. With a small screwdriver or a strong fingernail, pull back the plastic pin and lift the cruise control cable (rear) connector from the throttle body bracket. Push the plastic snap at the end of the cable off of the post with your thumb and swing the cable up out of the way. Undo the throttle cable (front) from the bracket in the same way, then work the cable out of its groove and slide the barrel end out of the hole. Tuck both cable ends out of the way against the driver's fender.

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Remove crossover pipe Now that the penetrating oil has had some time to work, remove the studs securing the rear of the crossover pipe to the rear manifold and remove the crossover pipe from the car.

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Remove and clean throttle body Undo the 8mm bolt holding the top of the throttle body brace and loosen the bolt on the LIM holding the bottom of the brace. The bottom of the brace has a slot and can be removed with just a turn of the screw in the LIM. Remove the three 10mm nuts holding the throttle body to the UIM and remove the throttle body. Some coolant may drip down onto the transaxle. With the plastic or rubber handle end of a small screwdriver, open the throttle plate to the full open position and gently push and lightly tap the MAF screen out of the throttle body. Use a soft brush, like an old toothbrush and one or two cans of throttle body cleaner to remove any carbon from the throttle body, throttle plate, and the IAC passages.

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Remove UIM Carefully remove the nylon accessory vacuum line from the rubber elbow and the large rubber vacuum line for the power brake booster from the fitting on the back of the UIM. Try not to break the old fitting as the new one may sit at a less convenient angle and you may want to re-use the old one. Remove the 5/16" bolts and 10mm stud securing the UIM to the LIM with six-point sockets. Move the wiring harness and any vacuum lines out of the way and lift the UIM up and off of the LIM. If it seems to be stuck, check to make sure you have removed all of the bolts. Bump the UIM with the heel of your hand if needed to break it loose.

Detach tensioner assembly Spray penetrating oil in the o-ring bores of the water pump assembly, tensioner assembly, and LIM to ease disassembly. Note: Some mechanics leave the tensioner assembly in place on 95-98 models because the cast aluminum nipple can break when it is removed from the water pump bore, necessitating replacement of the tensioner assembly. I prefer to detach the tensioner assembly, inspect the sealing surfaces and replace the o-ring seal in order to minimize the possibility of future leaks. To detach the tensioner assembly, remove the two remaining 13mm bolts securing it to the engine and wiggle it straight out. Realize that there are two o-ring seals that you are unseating - one connecting the tensioner to the water pump, (part of the aluminum casting on the 95-98 models, plastic elbow on 99+) and one on the plastic elbow from the tensioner to the LIM. If the plastic elbow breaks off in the bore of the LIM, you can use the head of an aluminum gutter spike or another soft tool to coax out the broken piece. You must be careful not to scratch or gouge the bore where the new elbow o-ring will seal.

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Disconnect EGR corrugated pipe Remove the 10mm or 13mm bolt in the steel block holding the corrugated stainless steel EGR tube to the outside of the LIM under the throttle body. Gently wiggle the pipe out of the LIM. Do not bend the tube more than necessary, they have been known to crack causing driveability problems. Use a mirror or disconnect the other end of the pipe from the EGR fitting at the valve to carefully check the pipe for cracks.

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Remove Thermostat Remove the two 10mm bolts attaching the upper radiator hose fitting to the LIM. It is not necessary to remove the fitting from the hose. Swing the hose out of the way toward the front of the engine compartment. Pull the thermostat out of the LIM.

Remove Residual Coolant If you have a hand-held vacuum pump, or a wet-vac, use it to remove as much residual coolant as possible from the LIM. Vacuum from both the elbow opening on the passenger end of the LIM and the thermostat opening. Lubricate the LIM elbow bore with a little silicone grease and temporarily install a plastic elbow into the LIM bore as shown to keep the last few drops from spilling into the crankcase when you lift out the LIM.

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Remove LIM Remove the two 13mm torx bolts holding the alternator support bracket to the rear cylinder head. Remove the 13mm torx bolt holding the purge solenoid in place on the front cylinder head. Remove the bolts securing the LIM to the cylinder heads with a 3/8" socket. There are two hidden bolts - one on the front of the LIM driver's side, one on the passenger side rear of the LIM. These bolts sit lower in cast depressions and will likely be partially or completely covered with oil.

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Slide down the flexible foil heat shield and undo the coolant temperature connector from the driver's front corner of the LIM. Lift the LIM keeping it level from end to end and from side to side to prevent coolant from spilling into the engine. If the tensioner assembly was left in place, the LIM is removed by lifting the driver's end causing the coolant elbow on the passenger end to rotate in the tensioner bore. Once free of the cylinder heads and side rails, the LIM can be pulled off the coolant elbow toward the driver's side. The procedure is reversed for installation.

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Spilled coolant in engine If, while removing the LIM, you spill coolant into the crankcase (the rectangular area between the heads), remove the drain plug from the oil pan and drain the oil. With the drain plug out, pour at least a couple of quarts of oil into the crankcase across all of the parts between the heads to flush the coolant out of the crankcase. If you spill coolant into an intake port on a cylinder head, first try to remove the coolant with a wet-vac or by absorbing it with a rag. This should account for most of the liquid if the intake valve was closed. Next, remove the spark plug from that cylinder, and rotate the engine by turning it by hand to expel any coolant that might have drained into that cylinder if the intake valve was open or not tightly closed. This is necessary to prevent a possible hydro-lock condition that could result in a bent connecting rod when you attempt to start the engine. Replace the spark plug when you are sure any standing coolant has been removed. Do not pour oil into any of the intake ports or any other openings on the cylinder head.

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Clean heads Cover the crankcase with clean shop towels so that scrapings do not fall into the engine. Using a heavy, flat-blade scraper, and a vacuum cleaner, carefully remove any clinging material from the surface of the heads and from the block side rails where the new gaskets will seal. Keep the blade flat, and the vacuum close to prevent any material from falling into the coolant or intake passages or the bolt holes. Blow out the bolt holes with compressed air. If compressed air is not available, make sure bolt holes are open and clear of any standing oil, coolant or debris using a vacuum cleaner, bits of rag, and a small screwdriver. Clean excess oil from the bolt holes using brake parts cleaner. Dry the bolt holes with compressed air or by hand with rags and a small screwdriver. Use brake parts cleaner on a clean rag to remove any oily residue from the sealing surfaces. Do not worry about stains on the cylinder heads. As long as any clinging material (including heavy oxide) has been removed and the sealing surfaces are not badly pitted, the new gaskets will seal. Do not use abrasive discs to polish the sealing surfaces of the cylinder heads. They may make the surface look better, but they will not make the new gasket seal better, and the abrasive dust generated will accelerate engine wear. If you accidentally drop more than a few bits of debris into the open crankcase, the only sure way to remove them is to flush the crankcase area between the heads with light oil and remove and clean the oil pan. The mesh strainer on the oil pump intake tube at the bottom of the oil pan will prevent larger bits of debris from entering the pump, but will not stop particles smaller than, say, table salt from entering and damaging the oil pump. If there are enough large particles of old RTV silicone, gasket material, or other debris, they may become stuck on the oil intake strainer starving the oil pump. This would be disastrous for your engine. It is a lot cheaper and easier to be careful in the first place.

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Clean LIM; install rd pipe: Empty any oil and coolant from the LIM. Use kerosene and a pan and a brush or solvent and a pan to remove any dirt or grime from the surfaces. Clean the sealing surfaces of the LIM with a scraper. Be careful not to gouge the soft aluminum with the corner of the tool. Do not use abrasive discs on the LIM. It is very easy to create low spots that will prevent proper sealing.

Use a straight edge and a feeler gauge to check the flatness of the sealing surfaces on the LIM. If you can slip anything larger than a 0.006" blade under the straightedge, consider replacing the LIM. A warped LIM may be seal for a while, but is likely to induce premature gasket failure. If the LIM is found to be warped, check the flatness of the cylinder head in a similar manner. You should not be able to slide anything larger than a 0.003" blade under the straightedge on the cast iron cylinder head sealing surface. Inspect the sealing surfaces carefully. If deep pitting is found on the LIM where the silicone beads touch the surface, purchase a good used LIM from a salvage yard.

Use steel wool and solvent to clean the injector bores in the LIM and the o-ring bore for the coolant elbow. Apply a thin layer of silicone grease to the injector o-ring bores and to the coolant o-ring bore. If you do not have a new gasket for it, do not remove the curved cover (coolant passage) under the fitting for the corrugated EGR tube on the driver's end of the LIM. Be careful not to damage the temperature sender under the front driver's corner of the LIM. If the stovepipe is stuck in the LIM, insert a close-fitting socket inside the pipe, then grip the outside of the pipe with a pair of vise-grips. Twist and lift to remove the old pipe. Clean out the bore for the stovepipe to remove any carbon. Set the LIM on a couple of 2x4s and tap the new reduced diameter pipe in place. Use a deep socket that just fits around the pipe and bears on the shoulder to drive the pipe down into the bore. Remove any oily residues from the sealing surfaces with brake parts cleaner.

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Clean bolts for LIM and UIM Clean with solvent and wire brush the bolts for the LIM and the UIM. They need to be clean and dry for the threadlocker to adhere properly and for proper indication of torque.

Install new LIM gaskets With the side rails and heads clean, and degreased with brake parts cleaner, place a bead of RTV silicone along the cast iron side rails. Then place the side rail seals so that the plastic locating pins fit into the holes (mid 97 - up) or hang over the outside edge of the rail (95 - mid 97) Check the aluminum frame gaskets for flatness. They are very soft and can be bent or straightened easily by hand. Place a small, ½" long bead of RTV silicone on the top of the ends of the rail seals, against the cylinder heads. Place the aluminum frame gaskets on the heads with the locating pins into the holes in the heads. Place another small bead of RTV silicone in the corners on top of the aluminum gasket and silicone rubber rail seal.

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Drop the LIM in place Holding the LIM above, without touching the new gaskets or end seals, line up the bolt holes and carefully lower the LIM in place minimizing any sliding across the end seals. Check the alignment of the bolt holes on both heads. Apply blue thread locker or thread sealant to the first five or six threads of each bolt, then start the bolts into each hole a few threads only. With all bolts in place, use a 3/8" six-point socket and an extension with no handle to run the bolts in all the way finger-tight in sequence. The tightening sequence starts at the center of the LIM and progresses side to side and outward to the ends. Torque the bolts in sequence in at least two passes to 11 ft-lbs. Attach the corrugated EGR tube to the fitting at the EGR valve and to the driver's side of the LIM by wiggling the tube into the bore then securing the steel block with the 13mm or 10mm bolt. Replace the coolant temperature sender connector and wiggle the corrugated heat shield back up into place.

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Change out o-rings and sleeves on injectors The APN kit provides 12 new o-rings and six sleeves to replace the old parts on the fuel injectors. The sleeves may not fit and the APN o-rings may be too large for the nozzle end of injectors used in newer engines. If you find that to be the case for your car, check with the dealer or your local auto parts store for the correct parts. Unless the sleeves are damaged, they can be re-used, but o-rings should be replaced. Make sure to cover or plug any holes into the engine before working with these small parts. Use a screwdriver under the curved end to pry off the spring clip that locks each injector to the fuel rail. Lubricate the bore with some oil, then twist and pull the injector out. Carefully pry the old o-rings out of their grooves and use a small screwdriver to slide the sleeve off of the end. Wipe the injector clean and install a new sleeve and a new o-ring on each end. Coat the o-rings with a thin layer of silicone grease. Twist and push the injector back in place in the fuel rail and slide the spring clip back in the groove to lock the injector in place.

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Install tensioner Clean the tensioner and water pump o-ring bores with steel wool, then apply a thin wipe of silicone grease in the bores with your finger. Install a new o-ring (or elbow) on the tensioner to water pump fitting. Coat all the o-rings with a thin layer of silicone grease and push the tensioner into place. Install the two 13mm bolts on either end of the tensioner assembly. The third, center bolt will be installed when the alternator is replaced.

Install UIM Fit the J-shaped, plastic PCV tube with the short end up into the PCV chamber on the passenger end of the UIM. Snap the long straight part of the PCV tube into the clips on the UIM gasket. Fit the plastic dowels on the UIM gasket into position and attach the gasket to the UIM. Check carefully to make sure the gasket fits around the runners completely and is lying flat. This may take a little adjustment. The runner insert on the UIM is separate and will move a bit to allow for a better fit on the gasket.

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Wipe the top surface of the LIM where the UIM will seal with brake cleaner and a lint-free rag. Set the UIM down on the LIM making sure the locating dowels are in proper position. Do not be alarmed if the new stovepipe is not exactly centered around the passage in the UIM. Look in the PCV valve chamber and make sure the end of the plastic PCV pipe is not all the way up against the top of the chamber as shown in the image below. If it is, carefully tap it down about 3/8 of an inch. Shine a flashlight in the throttle body end of the UIM and make sure the PCV pipe is still in the clips.

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Apply blue threadlocker to the UIM bolts and install all of the bolts part way into the holes. With a six-point 5/16" socket (and one 10mm) and using an extension without a handle, install all of the bolts finger-tight in sequence from the center to the ends and side to side. Make sure all of the bolt flanges clear the plastic alignment lugs on the UIM.

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Torque the UIM bolts in at least two passes to 89 inch-pounds or 7.5 ft-lb. Install the PCV valve in the PCV valve chamber making sure there is only one o-ring on the bottom of the valve. The cap for the PCV valve chamber provided with the APN kit is designed for engines with newer style MAP sensors. If your engine does not have a MAP sensor, or the clip is different, re-use your old PCV valve chamber cap. Lubricate the large top o-ring and use a socket and extension to push and twist the cap into place. Do not apply any significant torque to these plastic parts.

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Install fuel rail Swing the fuel rail back down into position with the four hold-down brackets over the studs on the LIM. Working back and forth with the front and rear rail, place each injector into position over its bore and push each rail down into place. The greased o-rings and bores will greatly ease this process. Install and tighten the four 10mm nuts.

Install alternator Place the alternator back in position on the engine. Plug in the voltage regulator connection. Make sure the wiring harness is low and against the UIM. Install the 13mm bolt (low center) and the 13mm stud (right) on the front of the alternator. Install but do not tighten the 10mm bolts that secure the rear brace for the back of the alternator to the bracket on the rear cylinder head. Start and run nearly all the way in the 13mm bolt on the left front of the alternator that threads into the rear brace. Tighten the two 10mm bolts on the brace. Tighten the 13mm bolt on the front. Attach the vacuum manifold fitting into the UIM and reattach the nylon accessory line and the rubber hose for the power brake booster. With the two 10mm bolts, install the front brace for the rear of the alternator on top of the wiring harness making sure the vacuum fittings remain secure. Reattach the output cable with the 13mm nut and snap the plastic cover back in place. Replace the bracket between the front stud on the alternator and the stud under the ICM; install and tighten the two 13mm nuts.

Replace throttle body Make sure a new gasket is in place on the UIM, then install the throttle body on the three 6 mm studs securing it with three 10mm nuts. Be careful not to over-tighten the throttle body nuts on the studs. You should not apply more than about 7.5 ft-lb (89 in-lb) of torque to these nuts. A new, soft gasket for the throttle body and minimal clamping force are needed to minimize warping of the plastic sealing surface. Some suggest that a black GM throttle body gasket is softer than the orange gasket supplied in the APN kit and will be less likely to warp the sealing surface over time. Attach the support bracket between the throttle body and the LIM and tighten the two 8mm bolts. Fit the barrel end of the throttle cable into the hole and the cable into the groove under the tang. Slide the plastic clip down onto the bracket until the clip snaps into the hole. Push the plastic end of the cruise control cable onto the post and clip the cruise cable onto the bracket. Replace the EGR heat shield with the 10mm nut on the UIM stud, and the 10mm bolt into the alternator bracket. Replace the MAF sensor, and the IAC. Reconnect the electrical connectors to the EGR valve, MAF, IAC, and TPS. Clip the wiring harness onto the heat shield.

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Replace exhaust crossover Inspect the sealing surfaces of the pipe ends and manifolds. Remove any rust that may prevent a good seal. Wire brush the bolts and studs. Coat the threads with high-temperature anti-seize compound. Place the crossover into position and run the bolts and studs in finger-tight. Keep the flanges on the crossover parallel to the manifolds. The space between the flange and the manifold should be equal side to side. Wiggle the crossover to make sure the pipe is seated. Tighten the bolts. Install the heat shield on the rear and tighten the nuts.

Install serpentine belt
Route the belt around all of the pulleys except the alternator. With a 15mm socket and long handle, turn the nut on the idler pulley on the tensioner assembly counter-clockwise to loosen the belt. Using only your hand, slip the belt over the alternator pulley. Release the spring tension to tighten the belt. Check all the pulleys to make sure the belt is properly seated.

Drill thermostat If your thermostat does not have an air bleed, drill a 1/16" or 5/64" hole in the flat flange of the thermostat just inboard of the rubber seal.

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Replace wires and connectors Re-route the spark plug wires and connect them to the coil posts. Re-connect all of the fuel injector connectors, and the MAP sensor connector. Carefully check over the wiring harness to make sure all of the connectors are in place and tightly snapped.

Attach lower radiator hose Re-attach the lower radiator hose on the nipple and tighten the clamp.

Get rid of the Dex If your car has Dex-cool coolant, this would be a great time to flush the system and re-fill it with "mixes with any color or type" coolant. Here is a link on how to flush your cooling system. Reverse Flush Procedure

Refill coolant Fill the engine at the thermostat housing up to the thermostat opening. Then fill the radiator until the coolant begins to overflow at the thermostat opening. Install the drilled thermostat with a new sealing ring and the air bleed at the highest position (12:00 O'clock). Install the hose fitting using a new paper gasket. Install the upper radiator hose. Top up the radiator and fill the expansion tank to an inch above "full hot." Replace the radiator cap. Techinfo Coolant Fill

Replace vacuum lines Re-attach the purge solenoid valve to the front cylinder head with the 13mm torx bolt. Reconnect the lower vacuum fitting on the throttle body to the front fitting on the purge solenoid. Reconnect the top tee fitting on the throttle body to the fuel pressure regulator and transmission vacuum modulator.

Connect negative battery cable With a 5/16" wrench attach and tighten the negative battery cable.

Replace air intake Replace the MAF screen in the throttle body taking care to keep the screen aligned and using only your fingers near the edges of the screen. Replace the spring retainer. Check to make sure the vacuum lines to the charcoal canister (and vacuum modulator, if equipped) are secure and in good shape. Replace the air intake fitting the rubber collar back onto the throttle body. Replace the two screws holding the air box to the radiator support. Snap the connector for the intake air temperature (IAT) sensor back into place.

Change oil and filter Change the oil and filter. If there was coolant in the oil, plan to run the car to operating temperature, and change the oil and filter again in an effort to remove any residual coolant from the engine bearings.

Start engine Start the engine and check for coolant and vacuum leaks. When the engine reaches operating temperature, open the bleed valve on the upper radiator hose fitting and rev the engine to about 2000 rpm a few times to expel any air from the cooling system. When the air is bled, only coolant will flow when the valve is opened. Gearhead Dick reminds you if you had an internal coolant leak, it is normal for white smoke to come out of the exhaust until the heat from normal operation can completely evaporate any coolant that may have accumulated in the exhaust system. Depending on the amount of coolant present, this may take a couple of days to completely disappear. Also, expect quite a bit of smoke as any anti-seize, oil or coolant burns off the outside of the exhaust manifolds and pipes.

Replace engine cover If it is winter or you want your engine to be a little quieter as heard from outside, re-install the engine cover. I like to keep mine off, especially in the summer, to encourage better engine cooling.

Replace splash shield When you are sure you have no leaks from the radiator fittings, replace the splash shield using the smaller bolts up front and the larger ones on the sides and in the rear.

Monitor coolant level Monitor the coolant level in the expansion tank, and for the first few days, check the coolant level in the radiator when cold. The coolant should be all the way to the top of the radiator filler neck. You may need to add 50/50 coolant to the expansion tank a couple of times to maintain the level at "full cold" checked with the engine cold. The level should stabilize within a couple of days.

Thanks to the Gearheads and administrative staff for reviewing and helping to edit this text, and to Scott for taking the photos.

_________________
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1998 3.8 Dodge Caravan 214K
2000 3.3 Dodge Caravan 175K
1949 Plymouth Special Deluxe 4-dr sedan 25K (needs some work!)


Last edited by bill buttermore on Tue Feb 22, 2011 4:28 pm, edited 30 times in total.

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