Weird Engine Sound after Head Gasket

[DirtyMech]

I did a head gasket recently on a 2000 Intrepid. It has a a V6 DOHC engine with 4 camshafts and 3 timing chains. After the job, the car now makes a hard cranking sound while at idle, which sounds almost identical to a diesel engine, though perhaps a bit louder. The sound is most noticeable at idle and does not become louder with acceleration.

 

I was wondering if any of my fellow Subaru driver-mechanics have had a similar experience that might explain this sound comming from a gasoline engine. I'm a bit afraid I might have messed up something. My potential guesses are:

 

- One of the header or EGR exhaust gaskets. I resued all the gaskets except the head gaskets (the guy was cheap).

 

- The cranshaft pulley might be too loose. I wasn't able to get it very tight because its an automatic and I had no grabber tool. I noticed a moderate wobble in the crankshaft pulley after the job as well.

 

- Loose camshaft. The front cap for one of the four camshafts had both bolts round out slightly in their bores, so only 8 of 10 bolts are snug on it. These are the only bolts that rounded out during the job.

 

- Bad cylinder seal. I haven't had a chance to do a cylinder pressure test, but will do one soon.

 

I doubt its the timing chains because the car accelerates and idles smoothly (except for the noise)! Could any of these, or some other thing, cause a diesel-like sound from a gasoline engine? Thank you for all input.

[Reveeen]

I resued all the gaskets except the head gaskets (the guy was cheap).

 

Then you should have sent him somewhere else.

 

The front cap for one of the four camshafts had both bolts round out slightly in their bores, so only 8 of 10 bolts are snug on it.

 

These engines are, well, what they are. You will get all kinds of strange noises out of them if things in the cam, chain, front pulley/damper, aren't within spec, noises such as you describe (though I like the sound of a diesel engine), even switching the rotational direction of the cam chain (re-using the old one, flipping it around) can cause a noise as the chain, and gears, take a "set" to them. . The crankshaft end play can be excessive, and just by disturbing the front, can cause a sound like a bad rod (not quite the noise you describe). These engines are the "bic lighter" (cheap, and disposable) of the auto industry.

 

All you can do is take it apart, carefully inspect EVERYTHING, replace anything questionable, and re-assemble carefully to spec.

[DirtyMech]

I resued all the gaskets except the head gaskets (the guy was cheap).

 

Then you should have sent him somewhere else.

 

The front cap for one of the four camshafts had both bolts round out slightly in their bores, so only 8 of 10 bolts are snug on it.

 

These engines are, well, what they are. You will get all kinds of strange noises out of them if things in the cam, chain, front pulley/damper, aren't within spec, noises such as you describe (though I like the sound of a diesel engine), even switching the rotational direction of the cam chain (re-using the old one, flipping it around) can cause a noise as the chain, and gears, take a "set" to them. . The crankshaft end play can be excessive, and just by disturbing the front, can cause a sound like a bad rod (not quite the noise you describe). These engines are the "bic lighter" (cheap, and disposable) of the auto industry.

 

All you can do is take it apart, carefully inspect EVERYTHING, replace anything questionable, and re-assemble carefully to spec.

Yea I should have. Ho well.

 

Thanks Reveen. Will do. New exhaust gaskets, timing chains, and tighter dampner...but fixing the 10mm head cam bolts in an aluminium head would be near impossible, no?

I suppose I would notice the camshaft slightly loose if I removed the cover once more and tried to jiggle it.

[idosubaru]

there's also a non-subaru discussion forum i believe. this thread might end up there if you can't find it.