A Rattling sound at rear of engine... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 05-24-2003, 09:53 PM   #1
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Default A Rattling sound at rear of engine...

Sounds like its directly underneath the rear valve cover. I asked a mechanic and he said he could hear it but didnt think much of it (wasnt a real top-notch mechanic), but I really want to know what it is. It bugs the hell outa me, its not loud and you cant even hear it when the car is moving.

I found where it was rattling at using a garden hose but I am not extremely knowledgable in all things mechanical and dont have any idea what it would be. I made sure it wasnt my exhaust or anything external.

I noticed my car also shakes very slightly at idle every couple seconds. Other than that it runs great, has no problems when I am driving and even drives fine a WOT.

I ordered a Chilton manual for bonnevilles at the local Hastings and will get it in a week or so, but they dont always answer these type of questions. They just tell ya how to take **** apart.

Any help greatly appreciated
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Old 05-25-2003, 06:22 PM   #2
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Can you get car up so you can get under it? I had similiar sound and it ended up being cat converter. These engines are pretty tough, but I guess it could be valve train. Compression and leakdown test would give an idea if it'* valve train or combustion area related. Is it a tick or more solid sound?
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Old 05-26-2003, 03:27 AM   #3
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Its kinda of a constant rattle at idle, very slight. I could get underneath it but I am pretty sure its under the rear valve cover on top of the engine, ill try it anyhow. Also my car doesnt really "shake" it kinda shudders when it idles.

Could it be a lose lifter/piston? dunno how that would be fixed.

It drives like a new car and gets about 50-55 on the oil pressure gauge, at hot idle it goes down to 40 sometimes, maybe 35 at the least. The original owner used it for highway use, almost solely.
Definetely not a tick.

I am guessing the 2 problems are related, but they may not be.
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Old 05-26-2003, 04:12 AM   #4
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Sometimes my car will rattle or shake slightly at idle also. I can feel it through the brake pedal, if that makes sense. It is bugging the hell out of me, even though it happens very rarely. It may not be the same problem but I hope I find out the problem. Misfire?? I don't know. Anyway, I'm changing my plugs (cheap Bosch) to AC Delco, and installing my Taylor wires tomorrow. Hopefully it won't happen again.

I also had a rattling sound from what I was sure was the Cat converter. It happened at idle and got quieter when driving. Somehow I haven't heard it in several months.
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Old 05-26-2003, 03:22 PM   #5
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If I have a soft motor mount will it cause the engine to move more than normal or does there have to be a problem to have the engine move at all when idling?
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Old 05-26-2003, 05:56 PM   #6
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Yeah I dont think its a MM. I had this problem and I was told by someone to put a bottle of Mystery Oil in my oil next time I changed it. Anyways I canged it and put it in.. I also put some In my fuel. This stoped my knock/tick/tap. I suggest you do the same. Its cheap stuff and it will supprise you in what it does to your engine.
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Old 05-27-2003, 02:45 AM   #7
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Ya it wouldnt surprise me if it was due to a buildup of crap in my engine. I dont know how regular the people that had the car before me had the oil changed. I ran it in my fuel for a week and it cleared it completely out but havent ran it in my oil yet. Its only been 500 miles since I changed my oil so it may have to wait a while.

I'll get one of those flush products and put itin there. They always worry me though cause they say add it on top of your old oil. I was always afraid it could screw something up having a quart extra of fluid in my oil.
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Old 05-27-2003, 10:37 AM   #8
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I run slick 50 in my car when I change my oil and it seems to work good but that mystery oil is awesome.
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Old 05-27-2003, 11:45 AM   #9
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Hi

Try a double treatment of auto-rx. I hear its excellent at clearing out sludge and other combustion matter.
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Old 05-27-2003, 12:35 PM   #10
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Whats that stuff lght1? Where does it go in the engine or in your fuel? Just wondering
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