Questions and Answers
Knocked Up Olds
Q. Hi, I have a 1992 Oldsmobile Cutlass Supreme Convertible with a 3.1 liter engine and 4-speed automatic transmission. The car is a fuel injected V-6 and has all the bells and whistles that were available (air, power everything, etc.) The car has 140,000 miles on it.
Recently, I have noticed a "knocking sound" that is louder under the car than from above, and appears to be towards the front of the engine (passenger side since this is transverse mounted). The knock increases with an increase in engine RPM. At first, the knock was only very intermittent and after the engine was hot, but now, the knock is constant (hot or cold) and is very noticeable at idle. I have attempted to locate the knock with a cheap mechanics stethoscope, but really haven't had much luck, mainly due to the cramped engine compartment.
I am the sole owner of this car, and have tried to religiously take car of it. I have used Mobil 1 in it for the last 90,000 miles. My fear is that this is either a connecting rod bearing knock or a main bearing knock. Is this engine known to have those types of problems at this milage? I had hoped to not have those problems based on using the synthetic oil and proper maintenance.
Thanks for your help!
DavidA. Well dave, I wish I could tell you it's nothing to worry about, but I can't. From what you describe it is a bearing knock, most likely a rod bearing.
First thing to do is to have the oil pressure checked with a mechanical gauge and make sure the knock is not the result of low or no oil pressure. I doubt this is the case, but still worth checking.
If the knocking recently started and the damage is not too severe, the connecting rod bearings can be replaced without an engine rebuild. I have been pretty successful replacing rod bearings in engines that are knocking. It all depends on the guy doing the job. The rod bearing journals have to be polished well and accurately measured to get the correct bearings.
If done with care, this repair can be permanant. As to why it went at this milage, all I can say is it happens. Some go 200,000 miles without a problem and some kick the bucket at 50,000 miles.
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