1987 944 (non turbo, non S2)
208,000 miles on the odometer

I recently dropped my 944 off at the shop with a charging issue. The symptom was a 2 volt draw and the alternator was diagnosed as the culprit. As it was put to me, there was something inside the alternator that was causing the problem and has been replaced. I can only assume what happened next is not related.

While undergoing a test drive by one of the shop techs, the motor developed a disturbing "rattle". So severe was the rattle that the engine was switched off for fear that a connecting rod was about to come through the block. I never heard the rattle so am taking their word on the severity of the noise. They re-started the motor and listened to the rattle in an attempt to diagnose the source. They determined that the rattle is temperature as well as load sensitive and the rattle increases as the temp. increases and the oil thins. Oil pressure was good and there was no metal in the oil pan or on the drain plug upon inspection. They felt the rattle was emanating from either the #3 or #4 connecting rod and that it was undoubtedly a connecting rod bearing. They have removed the sub-frame, raised the motor and removed the oil pan. The bearings have been removed and determined that they only showed signs of normal wear and are not worn enough to cause this. A new set will be rolled in. They have also determined (without removing the head) that the wrist pins and bushings are okay and that there is no significant play. The crankshaft looks good, the con rod bolts look good, using a boroscope the tops of the pistons look good and that there is no significant carbon build up. Their suggestion to me now is to put it back together, run it and see if they can't determine what else may be causing the rattle. This does not set well with me for I fear that it will just have to come back apart or worse--cause a catastrophic failure.

Can anyone think of anything that may simulate a bottom end failure sound yet isn't?

Oregon Region PCA Member

 

Was the "rattle" just a sound within the engine/oil pan, or was there actual movement/vibration of the engine? My thought upon reading was "rod bearings", but once you addressed that, my next thought is: when was the last time the engine mounts were replaced? Or, possibly some loose/broken hardware on the engine mounts? What about a broken balancer belt, or a broken/loose balance belt tensioner that has allowed the belt to skip teeth? Curious. . . keep us updated, please!

PS, might want to also post this up above in "Water Cooled > 924/44/68" - seems to get a lot more traffic than down here in the model specific forums.