'95 Buick Riviera Supercharged Engine Knocking

[Red-Z]

My wife has a '95 supercharged Riviera. The engine became overheated and blew a headgasket. After repairs, the engine has a loud knck with the frequency of a valve tap. Can anyone help me diagnose this?

 

[cabech984]

Who did the repairs? Can you determine if its top end or bottom end knock?

 

[Red-Z]

Who did the repairs? Can you determine if its top end or bottom end knock?

A local auto shop replaced the rear head, head gasket, and did the valve job. The sound is louder overhead than it appears underneath. It sound louder in the front than the rear.

 

[cabech984]

And you know for a fact that it didnt do it before the repair? How long were you driving it w/ the blown gasket before the repair was made? Could have spun some bearings if you had alot of coolant in the oil. I'd take it back to the shop and see what they advise.

 

[Red-Z]

And you know for a fact that it didnt do it before the repair? How long were you driving it w/ the blown gasket before the repair was made? Could have spun some bearings if you had alot of coolant in the oil. I'd take it back to the shop and see what they advise.

I drove 30 milesbefore repair. Shop thinks it may be a deformed wrist pin, but I don't trust this advice since it is often a misdiagnosis. What else could it be?

 

[eastwoodad]

I would rule out that it isn't an exhaust gasket first. That is quite possible since they had to remove the head and believe me an exhaust gasket can make some racket!! I would rule this out first, though it sounds like it is internal.

 

[Red-Z]

I would rule out that it isn't an exhaust gasket first. That is quite possible since they had to remove the head and believe me an exhaust gasket can make some racket!! I would rule this out first, though it sounds like it is internal.

It sounds louder from above the engine than underneath. It sounds louder from the front of the engine than the rear. It was the rear head gasket that blew and was replaced. what else could it be?

 

[cabech984]

Is there any way you can post a sound clip of the noise? 30 miles could have done some damage, but if it wasnt knocking during the trip and is now knocking, either you tore up some bearings or yes, the shop did something wrong repairing it. You should have them check the oil pressure w/ a manual gauge. does the driver info center on oil pressure? If so, what is it reading?

 

[Red-Z]

I couldn't tell if it was knocking before the repair because the blown head gasket was too loud. There is no engine oil gauge, just a warning light, but no warning. Valve lifters are quiet. It's a tap/knock sound and I can probably record it and convert to a wav file.

 

[Red-Z]

Is there any way you can post a sound clip of the noise? 30 miles could have done some damage, but if it wasnt knocking during the trip and is now knocking, either you tore up some bearings or yes, the shop did something wrong repairing it. You should have them check the oil pressure w/ a manual gauge. does the driver info center on oil pressure? If so, what is it reading?

It's a "Toc" sound

 

[garyk1970]

Ive heard a supercharger bearing go out knocking like crazy before,i was sure the engine was bad, the tech listened for a second and said ;nope bad supercharger...

 

[Red-Z]

This sound synchronizes with one cylinder, not a clatter like a bearing