Source of my noise

[Lightyear]

I think I've tracked down the mystery 'ghugging' sound on my '88 Burb. With a sthethoscope, there is a distinct metallic 'clang' coming from the left-hand cylinder bank. It is the loudest near the second cylinder from teh front on that bank. With the 'scope probe held to the injectors on that bank, the second one is louder than the others, and the noise is present there, as well. The right-hand bank has just normal valve train clatter audible with the 'scope.
I've read somewhere in these pages that a bad injector has an odd sound to it. I'm thinking of replacing the suspect one as a test, then all to match, if that's the right thing. If not an injector problem, is this likely a valve train problem?
Also, I pulled the turbo plenum chamber off today, and there was a lot off thick, crumbly black gook in there. Is this normal? If not, any remedies? Thanks, all.

Buzz

'88 Suburban 4x4, 6.2 w/Banks Sidewinder and TH700R4

[DmaxMaverick]

Try switching your suspected bad inj. with one on the opposite side. If the noise follows, it is the injector. If the noise is unchanged, it is not.

That thick black crud is a combination of CDR oil vapor and EGR gasses (if you have EGR). In most cases, as bad as it looks, it doesn't effect engine performance much, if any. If you have the intake off, clean it. Otherwise, leave it until you have the intake off for other reasons.

Good luck.

[john8662]

Would be nice to hear what you're hearing, but since you've narrowed it down to cylinder #3 (second cylinder on this side) on the Drivers' side cylinder bank I'd check the injector first. When it's making the noise, leave it running, and go grab a 3/4" open in wrench and loosen the nut going to the injector line at the injector. What you'll be doing is loosening it just enough for it to leak and this will stop that cylinder from firing.

Does the noise completly go away?

If so, and I mean COMPLETLY (it will quieten down most time, but not go away entirely) then it could be a failed injector.

Otherwise, it's compression test time, and thats fun in itself, better get yourself a helper!

About the black stuff, it's hard to tell, that stuff could have been in there from the time before the turbo was installed, because you've got a 1/2 ton that DID have a nasty EGR valve installed on it at one time. Perhaps the intake was never cleaned out? Otherwise it could be really oily from blow-by since these engines EAT their own blow-by and burn it for better emissions (and so you don't have to smell it).

[Lightyear]

I'll give that injector test a try in the next few days and report back. As far as the intake, I did have it off to replace a broken fuel line, and it had the same gook inside. I cleaned it out, thinking that all that junk had been in there forever. It's back, about six months later. Does the EGR REALLY serve a purpose? There are no emissions checks on my 'Burb here in GA. Is it worth it to remove the EGR? Will it run better? I do plan to keep the old beast for quite some time, so I'd like to make it run as well as possible. There are a few other bugs, but more on those later. Thanks for all the help so far!

Buzz

[Lightyear]

Here's the latest: loosened the suspect injector, idle dropped but no change in the noise. This morning, while squeegeeing off my mirrors, I noticed the mystery noise was quite a bit quieter right after an overnight cold start. Is this indicative of a valve train problem?
Also, by the gauge, I get 40psi of oil pressure cold at idle, but about 20psi hot. Is the oil pump on its way out? I think it's the original, now with 262K on the motor.

[john8662]

With that many miles it's possible that the oil pump is failing, but at this point I'd think that the lower oil pressure readings were due to wear from a larger bearing clearance. Sounds are usually quieter for several reasons when it's cold. The timing advance is on in the pump, this usually makes the engine louder and you don't hear the noise a bad. Also, the fast idle is usually on, and when your anything above idle, most noises are harder to hear. And finally, the oil is thicker when cold, takes up the void if there is one when it's colder, until it warms up.

Really, with those kind of miles, it's probably wise to keep driving and get your money's worth.

For the oil pressure, I'd sure verify that the gauge inside is close to accurate, by connecting a temporary mechanical oil pressure gauge. The factory gauge is known to be off about 10 psi, reading higher than it actually is.

[Lightyear]

Thanks; that all sounds logical. Is there anything I can do to prolong this engine? I'm the third (at least) owner. I have some records from the previous guys, but they are incomplete. Should I start a re-engine fund, and wait for the bearingd to give up? I really like my truck. It's a great vacation vehicle for me the wife and the dog, and it's perfect for my daily lap of the Atlanta 500. I'm new to diesel ownership, had the 'Burb for about 1-1/2 years, but I want to learn more. I don't see myself ever owning a gasser again. Thanks!