#3 cyl. noise iden?

[2369488]

Warmed up the car last Sat. drove about a mile (never over 2500 rpm). Engine just stopped no warning. I pulled the car over and restarted with no problem except a noise was coming from the engine like a value or rod was bad. Oil pressure is good - no change from normal. Noise appears to be coming from #3 cycl. removed valve cover everything tight nothing loose. Removed starter. Again everything looks OK but when the engine is started it has a major knock in the area of the #3 cycl. (1986 930 - 47K miles. Eng. refreshed at 40K, K27, Andial intercooler

Any thoughts on what the noise is?

[JFairman]

You could try removing the spark plug wire from that cyinder, or the others one at a time while it's idleing.
If it's rod knock the sound may change some.

It may be a bad idea (risk of more damage) to run it at all with it the way it is so... start it again at your own risk.

[WERK I]

I noticed in your post that you removed "valve cover". Did you remove both valve covers or just the one? With these engines it's pretty hard to isolate a noise, because they are so damn noisy to begin with. Go get a stethoscope at a parts house and it will help you isolate the sound.
What's disconcerting is the engine stalled when the noise first appeared. That makes me lean towards a spun bearing, but you said you never went over 2500 RPM.
This may sound silly, but check your spark plugs. A loose spark plug will give you a sound that you swear the engine is going to disintegrate.

[NathanUK]

Check your headstuds too after removing both valve covers.

[2369488]

I or I should say my mechanic used a stethoscope to isolate to the #3. I will suggest to him that he pull the spark plug wire on #3 to further confirm.

Thanks for the input. I'll keep you posted once we decide on a final course of action. It is looking more like we will need to pull the engine.

[spuggy]

Originally Posted by WERK-I

What's disconcerting is the engine stalled when the noise first appeared. That makes me lean towards a spun bearing, but you said you never went over 2500 RPM.

#3 or #6 are certainly the ones most prone to spin, I'm told. I span #6 bearing sub-3000 RPM in traffic, so it can be done.

About 1000 miles after an overrev, and I thought I'd dodged the bullet... A few weeks later still running great, shifted up into 3rd @ 40 MPH (915 box) and suddenly lost power when the clutch went home and I had to use surprising amounts of gas to prevent RPM dropping off. Then the scary noises started a few seconds later, when I was still thinking WTF?

The rod bolts can be over-stressed and just let go anytime afterwards they feel like, I think. My wrench says he's had 3.2's that just let go for no identifiable reason whatsoever (same crank, rods, bolts). I hate the factory rod bolts.

[2369488]

Thanks Spuggy. Your description of the bearing failure is very similiar to mine.