Hi,

I have a 2005 GXP with right around 160k miles on her... been a really good car. Got it with 35k so it doesn't really owe me anything - haven't had a lick of trouble with it other than the normal stuff... had to replace a water pump which was challenging for me at one point but once done has been pretty good. Anyway... my car has started making this rattling noise which sometimes it does it other times it doesn't. It will do it after being shut down for about 15 minutes and started back up and it's a fairly pronounced rattle. I don't think this is piston slap. My brother who is a mechanic of 30 some years is the one that had diagnosed it briefly as a cam bearing but whatever it is certainly is internal.

What I'm asking is for someone with some experience with the Northstar to let me know if this seems reasonable as to what I'm hearing? My brother said to put some slick 50 in it and see if it helps to quiet it down...

I have been running Amsoil in it 5W30 since the 35000 mark when I bought it. Car has not really been babied all that much. I tend to have a heavy foot and from what I was reading it sounds like the N* likes that to an extent but I'm worried with this issue that it might be made worse by hammering on it.

Anyway anyone that could chime in would be appreciated.

I wouldn't even mind doing an engine transplant if I could find someone in my area (West Michigan) who could do the job and not rape me on price. I know it's a job because it has to come out the bottom which is why my brother doesn't want to help me with it. He suggests I sell it sooner rather than later and buy something else but I really like my car and the body and everything is really good shape still.

Anyway I'm rambling now, but anyone that could chime in I would welcome.

Thanks,
Rich

You sure it's not just a noisey idler on the belt drive or, if he's isolated it to the cam covers, could it be the belt drive for the water pump. It's driven off one of the cams on the front bank.

Cam bearings don't "rattle". They either squeal/screech. It's metal spinning within a race or the crank running around in it without lube.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I'm not sure... is there a way I could diagnose it? Maybe pull the belt off the water pump and try starting it cold?

Also I should mention that it quiets down after the car is running for about 2-3 minutes.

Rich

It almost sounds like a belt tensioner. While watching the engine run, if you notice the tensioner wobbling around a bit, that's a key indicator that it's probably the culprit. I will very carefully, while the engine is running, gently push with a screwdriver, prybar, or similar on the tensioner and if, with my pressure on it (I'm essentially acting as the brace against it wobbling), the noise goes away, bingo.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

Are you talking about the water pump tensioner?

We also did a test on the alternator (my brother has a battery tester that is pretty good and can load the battery etc..) and with the car running the charge indicator is quite a bit above the "normal" green arc so maybe it could be coming from there?

Rich

Both. Both will have an idler/tensioner.

Here is a pic of the water pump on the driver side of the front bank. That forward one is the tensioner. You will have to remove a little black shield to get to it.



Alternator output has nothing to do with any issue you are describing here. I would suspect that while running, it should be putting out 14 - 15, heck maybe more volts.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I was just thinking alternator because it has 160k on it and it's the original - thought maybe the bearings might be going out on it's pulley not that the voltage really has anything to do with that. My brother thought that it might be over-charging my battery though. My gauge on the dash sits just north of 14v so I don't know if that is normal range.

I got the water pump belt off and the pulley on the cam has no play in it at all and the rattle is still there. Now I'm fighting trying to get the belt back on the water pump pulley... argh.

Rich

Will the car run without the drive belt? I could pull that off and start it up and see if it's making rattling noise.

It'll technically run. For how long?? The main thing it drives will be the alternator, which is what supplies the power to fire your ignition and power the electronics. If you're running that purely off the battery, you'll quickly kill it and at the same time, might cause other electrical issues as the system requires a minimum amount of power to run things.

If you take the one off your water pump, well, that won't turn and circulate coolant. That's never a good thing... Especially on an aluminum block and heads.

So I wouldn't recommend this avenue as a way to diagnose anything.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

Well only talking about running it for maybe 30 seconds to see if the rattle is there or not... but I don't know - I'm not a mechanic - just technically inclined as I'm an IT person... so I tend to try to troubleshoot things in whatever way I can wrap my head around it.

Ok well now I think the engine is done... I took the drive belt off and fired it up and the rattle/knock was there so I shut it down (ran for maybe 10-15 seconds). Put the belt back on and dumped the slick 50 in and fired it back up... rattle was pronounced and then got quieter but then I heard a couple of clunks and it continued to run.. let it run to warm up a little... all the while the noise was there but much quieter .. exhaust started smelling bad - not sure what it was.. never smelled like that before. Got in to shut it down and the SES light was flashing on the dash... I don't have my code reader to read the code at the moment (loaned it out) so I don't know what it is but can't be good - usually I don't think it flashes unless serious.

So... any suggestions as a trustworthy place in MI that could do a transplant either that or I'm on the hunt for another car....

Flashing SES is a misfire. It will be P0300 and P030x (the "x" is the individual cylinder(s) that are actually misfiring).

BTW, Slick 50 is horseh*t. I should've mentioned that before. I wouldn't put it in my enemies engine... NEVER put an oil additive in. It won't do crap and might actually hinder your oils' ability to do it's job. Most manufacturer's do dumb things, but one thing they're pretty solid on is their lubrication systems and the requirements for necessary lubrication. GM is actually one of the best out there at this. They set the standards for most oil grading and testing processes based on the engineering in their engines (think Dexos). My point being, if they wanted an oil additive, they'd have told you to put it in along with oil itself. For your engine they specify any oil that meets GM4718M (synthetic) or GM6094M (conventional) standards/specifications. You need nothing more, nothing less. Obviously any Dexos certified oil supercedes either of those previously mentioned standards.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

So what now? Change the oil? I've always kind of been of the same mindset as you on the Slick 50... I just did it because I trust my brother as he has been working on engines for over 30 years and seems to know his stuff. Normally I wouldn't put anything in - I run Amsoil in it because of the high quality of the oil. Reading another forum though they recommend just running normal oil in it that synthetic is not really necessary for the north star.

I'm not really sure what to do - misfire sounds right as it was running rough. I'm really concerned about the two clunks that I heard - they were not together.. maybe a minute or so apart.

Rich

Kinda hard to tell over the intertubez. The N* is an interference engine and if anything is out of timing, the valve(s) will kiss the piston(s). So I'm wondering if something happened to a cam chain, chain tensioner or teeth on the cam gears causing it to skip/jump timing. Which that might have been the noise you were hearing initially. However I don't know that I'd classify it as a rattling sound, more like a clunking if the chain is slopping around on the teeth.

I would drain it. As to what to put in, again, as long as it meets Dexos or prior GM4718M or GM6094M, that's all you need. Whether you put in synthetic of conventional is your wallets's choice, which right about now, I'd go with the cheapest considering the situation.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I had kinda ruled out timing chain related things just because I had read elsewhere that the chains and tensioners on the northstar are pretty bulletproof. Tensioners lasting up to several hundreds of thousands of miles and certainly outlasting the engine itself. It ran fine today up until I parked it in the garage... running pretty normal. The sound was there when I started it to come home and then went away when I let it sit for a few minutes before I took off.. but then it ran like it always does. Parked it in the garage and then did the two tests. Removed the water pump belt... ran it for 10-15 seconds - rattle/knock was there and shut it down (maybe the short starts were not good for it?) and then replaced that belt and removed the drive belt - same test. Ran for 10-15 seconds and shut down... Maybe I should have let it run each time for a minute or so to get the oil pressure up and the oil to the top end?

Draining the oil might be good as I could see if there is anything in it as far as metal or anything. I'll have to use a different pan because I have one of those enclosed ones with the hole in the center.

Rich

It's a pretty simple mechanical layout. but nothing is infallible and there is a reason the N* was discontinued.

N* cam drive;




I'm just trying to think of things here. Other thought, bent connecting rod(s)? This could happen from hydrolocking if enough coolant got in to the cylinder. And we all know N*'s have had head gasket issues...

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

I will have to come back after work and read through some of these. A few of you might know me from the Bonneville group on facebook, I own Northstar Performance in Ontario Canada.

I know a lot of people hate the Northstar but when the issues with these motors are dealt with, they are a wonderful powerplant that is very, very reliable and have a lot to offer. The 3800 L67 is a great motor as well, and I have had a couple of SSEI's and an Olds LSS with an L67.

Ok changed the oil... nothing really noticeable in the oil or coming out of the filter without actually cutting the filter apart. Finished the change - put new oil in and fired it up .. much quieter on start up... heard a couple of faint clank sounds... SES light on solid now - still running a bit rough - sounding like it's missing on one cylinder or something but apparently no misfire reported? What does a solid SES light mean? I can't read the codes presently.

Also the exhaust smelled normal this time. Didn't let it run too long - good oil pressure.

Rich

There are several 100 DTC's it could be. Without it being scanned, I can't armchair QB that one. But my guess is that it's something related to the misfires.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck