valve train noise or worse ?

A rapping noise on overrun as you describe sounds like rod bearings to me, GF had the same noise on her Corrado and new rod bearing shells made it go away

nate

Thanks, Nate,

If you're talking about low end bearings, it is relatively good news for repair. But how did it come ? Bad oil, bad load ? As I drive at low rpm, on low throttle, would that be enough for damage to occur in a short period of time ? I imagine oil pressure then doesn't get that high , ie. high enough.

This car ran fine for a long time, until there was an oil problem and fuel system issue, then after a power test it ran worse. It is possible the damage dates from then. But after letting the car sit for two years, at first there was no noise. I'm worried timing has been altered by someone turning the distributor 4 degrees, any-clockwise.

This distributor has a camshaft sensor, which doubles as a crankshaft sensor with magnetic markings. A mechanic said you could turn it as much as you'd like, the computer would still find the right TDP ? If not, could this have any influence on rod bearings wear ?

Thanks again,

Carl

Is the valve lash correctly set? Was it set to the correct gap with the engine at the proper temperature?

How do you know the valves were tightened too much.

A rattling or rapping sound can come from a lot of sources besides valves. An exhaust leak can make a rattly sound when cold, as can loose wristpins, main and connecting rod bearings as well as valves that are not correctly gapped. It is all but impossible to correctly diagnose the cause of noise from a written description on this or any other forum. I would suggest that you have an experienced mechanic disgnose the problem, preferably one familiar with whatever make of car you have.

What is an oil issue. Do you mean the engine was run without oil, or the oil was never changed?

How did you determine the ignition timing had been reset over such a wide range.

Don't start adjusting valves and replacing rockers before you know what the problem is. I would strongly suggest that a mechanic with the proper tools and training take a look at the car.

Yes, measured hot, set cold and verified hot. And reverified cold.

Because of the above, they were checked after a mechanic had adjusted them. They were 2/1000th of an inch too tight, some 3/1000th.

I'm trying to find someone. Had a bad experience with the last one.

The oil was overfilled to a level at least half an inch too high. in the end it, or what was left was removed, but the car consumed the quantity between the dipstick markings in about 1000 mi. There was no interest from the dealer to look into it, although it was strange, but I did not see this dramatic drop again (yet).

The distributor has been turned that much. But was it turned along time ago and has someone reset it to its correct position, or was it turned a while ago and reset, or is it set to less advance now ? I could not get an answer from the dealer, because he said turning a distributor does not affect advance on this ECU engine.

I did have to have the valve lash adjusted because it was much too tight. I asked some mechanics to look at it, but they are confident that this type of engine can stand anything, and never has problems.

Thanks again,

Carl

Actually in the case I'm referring to it was just a bad batch of bearings from the factory and a common, known problem with the G60 motors. I don't know if incorrect timing could affect bearing wear or not; I suppose if it were advanced enough that it was always detonating that that might happen.

nate

Possibly it did. Nice to have someone confirm my thoughts.

Thanks.

I can see valve noise being influenced by RPM (more RPM => more noise) but I'm unfamiliar with valve noise being influenced by throttle.

My experience with rod bearing noise is it is loudest when accelerating / hill climing (more engine power => more noise) and is quiet when off throttle.

I've been told the main bearings tend to be noisy all the time.

Now the "diminishes after about a second" makes me think gear lash. As in something is spinning and the normal resistance keeps the "front" side of the teeth engaged. When going off throttle the spinning item's inertia keeps it spinning so the gear is bouncing between the "front" and "rear" side of the teeth. When the engine speed stops dropping it's back to resistance / "forward" teeth. If the slowing is heavy then the inertia can keep the "rear" side of the teeth engaged.

Driving down a grade, off throttle, at a constant speed would create a similar force on the bearings as off throttle but no inertia / spinning changes.

Do you get the noise under this condition?

Or only when the engine is dropping RPM?

Hi,

That's a thought. This gearbox has given me trouble in the past. When starting up the car again, I will try what it's doing under the conditions you describe. A way to find out is IMHO to disengage the clutch and see if the sound has gone. If it is engine bearings - whichever - the clatter should persist, at least some.

Thanks for the idea.

Carl

"Brian Stell" schreef in bericht news:iR8Ee.5870$_% snipped-for-privacy@newssvr14.news.prodigy.com...

Does your car have a gear or chain driven cam?

A chain could also produce a "bouncing" between "front" of the chain pulling against normal resistance and "rear" of the chain pulling against the inertia to slow the rotation during dropping RPM.

Also, if the chain were stretched or the tensioner weak on dropping RPM the "front" side of the chain could loose and be flapping or banging around.

Again the condition would be dropping RPM (as opposed to constant RPM with engine braking).

Hi all,

I tried Brian's idea, but found that nevertheless most likely the big end bearings are gone.

Thanks Nathan. Hopefully not a big repair, if the problem is still not so old. But big end bearings wearing out can severely load connecting rods, and lead to failures and break-ups, so I just read.

Thanks all,

Carl "Peter" schreef in bericht news:uraEe.151044$ snipped-for-privacy@phobos.telenet-ops.be...

Hi Brian,

Seems we were at it at the same time :-)

No, this camshaft is belt driven, and it's not making noise. But your analysis is worth remembering, and very much appreciated !

Thanks,

Carl "Brian Stell" schreef in bericht news:LXxEe.20675$ snipped-for-privacy@newssvr13.news.prodigy.com...

If you can drop the oil pan easily, why not pull one rod cap and Plastigauge it, also see if you can "wipe" some copper on the rod journal of the crank with a penny. (no copper transfer = good, obviously.) If it passes both tests it's not the rod bearings, if the clearance is large but passes the penny test OK just roll some new shells in and try that.

I understand your concern that the rod bearings would be louder under load, but honestly in the G60 they could be heard most distinctly at about 3000 RPM, when the engine slowed down during a shift. It seems counterintuitive but there you have it.

When you put the new shells in, use lots of brakleen or similar to make sure that you don't have any varnish or gunk on the bearing surface of the rods or caps (will tighten up clearances and interfere with heat transfer) also crank the engine over with fuel disabled until the oil pressure comes up before trying to start it, don't want to dry start new bearings.

good luck,

nate

(I've probably just appalled all the real mechanics read> Hi all,

Hi Nathan,

Thanks. The oil pan cannot be dropped easily, and I'm not going to do the work. Is there any guarantee that the wrist pins are never as quickly damaged as the rod end shells ? It would severely heighten costs.

The counterintuitive reality is not so illogical, IMHO. There is a change in load direction after the compression stroke when throttle is closed, and so the movement causes a sound. With combustion the load is always positive. Only at intake stroke should the load change but even then would a closed throttle cause more shell noise. Am I right ?

What should I do if the penny test is not OK ?

Thansk again,

Carl

"N8N" schreef in bericht news: snipped-for-privacy@f14g2000cwb.googlegroups.com...