Coolant Leak Troubleshooting

[TenGHz]

I had a recent coolant smell coming from my car at startup, and got some help from a friendly local gearhead on trying to find the source. It was suggested to do a write up on what I did to try and find the leak (which is what this is). This is aimed more towards putting all the info in one place, which will help out any new guys with missing coolant, or coolant smells. If I miss anything, please be sure to add it. I put this in the 2000-2005 forum as this is what I worked on, but certainly most of this will apply to the older generations as well.


First things first would be to check for an UIM (upper intake manifold) problem or a LIM (lower intake manifold) gasket leak, as this is a big problem with our cars.

Pull out the dipstick to see what the oil looks like. It should look clean, and not like coffee with cream, or chocolate milk, and also should not be dark black. Also, you can wipe the dipstick off on a clean white rag, or paper towel. This will help to show off anything that shouldn't be there. It should look light brown with no other colors lingering. Next, pull the oil fill tube and the oil cap off the valve cover, and remove the engine cover. While the cap and fill tube are off, inspect the inside of it. There shouldn't be any milkiness in the tube or the cap. Also, look inside of the valve cover hole to see if any milky residue is there as well. If any of this residue is found it could be signs of problems with the UIM or a LIM gasket failing and leaking coolant into the lower part of the engine.

Next look at the top of the engine (with the engine cover still off) around the UIM and LIM gaskets. Look around the injectors for any puddling of coolant. The injectors look something like stubby sparkplugs, which will be right below some metal pipes (fuel rails). Also look inside of the valleys that the LIM makes. The coolant may also pool up inside these as well.

After this, start up the car and go around behind to the tailpipe. Look for any excessive steam coming out. Try to take a few good whiffs near the exhaust. If there are any sweet smells to it, or excessive steam, it could also mean UIM or LIM gasket failure. Another tip would be to hold your hand in front of the exhaust pipe and let some condensation build up on your hand. You can test this for any sweet smells as well.

If you have signs of UIM or LIM gasket failure, get it to a shop as soon as possible, and have them drain the oil. This is important, as if not done quickly, it could mean death to your engine. It is always good practice to watch the level in your reservoir tank and make sure no sudden changes in the level occurs.


Alright, if it appears that coolant is not leaking internally, it's time to look to the outside.

Start with the radiator cap, make sure there is no leaks or seepage there. Then check the hoses leading to and from the radiator. Feel around where they link to the engine and the radiator for any moisture there. Also look around underneath where the thermostat housing is. This should be the metal elbow where the radiator hose attaches to the top, driver side of the motor. Make sure no coolant is escaping around it.

Go back to the passenger side of the engine again. Look right below the black plastic UIM for a 90 degree plastic elbow right below where the UIM atteches to the LIM. Check this elbow for cracks. Then if you go straight back from this elbow, you will see another one. It will be slightly lower, and a bit of a pain to find. It'll be hidden by pulleys and the serpentine belt a bit. Check this elbow as you did the first one.

Now look at the heater hoses as well. They will be rubber hoses that run from the firewall to the passenger side rear of the motor (near the alternator). Feel along the hoses and their connections on the firewall and the motor to make sure nothing is leaking there.

You can also look around the water pump, which will be on the passenger side near the bottom of the engine. This is kind of hard to check from the top due to it's location, but you should be able to feel around it to feel for any fresh coolant.

The heater core itself could be another culprit of a leak. This will most likely cause a strong coolant smell inside the car. Fogging windows could be another sign of this being the problem.

Alright, this should be a really good running start as to what to check for when trying to find a coolant leak. Any input on anything else I may have missed, would be greatly appreciated.

[lash]

Good post Joshua!

I'd like to add that after you check for hose leaks etc in the engine bay, and if you do not find anything right away, before you move to the next step or give up:

1) Start car and run until it is up to temp. You'l know this by feeling the rad hoses. If they are hard, that means there is pressure in them.

2) Now carefully look at all the rad and heater hoses again. Pinholes that are not noticeable cold will often open up once the system is pressurized. A small pinhole can piss out a lot of coolant while you're driving and yet leave little to no evidence for you to find once you're stopped.

3) It is very helpful to view the water pump weepholes if you have one of those automotive mirrors...you know, the ones that are on an extendable handle and rotate around to look under and around things.

4) Be very careful while trying to diagnose while the engine is running! Loose clothing and body parts can get caught in moving belts and fans and the exhaust manifolds can leave quite a burn mark!

[TenGHz]

Thanks lash. It's a repost from BC. I was hoping more people would re-post the stuff they had added in my original one (there were some great extra tips). So your tips are very welcomed!

Feel free (anyone) to add anything that's missing. Keep it simple as I wrote the original thread for n00bs, like I was when I wrote it... lol