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Loud chattering noise from engine

This is in regards to a 1994 Chevrolet Corsica with a 6 cylinder engine and

165,000 miles.

I bought the car new in 1994 and have always used Mobile-1 synthetic oil with regular changes and have taken very good care of it. It has always ran smoothly with no problems.

A few days ago I started the car and a very loud chattering noise immediately began coming from the engine. I am sure that it is a rocker arm. I believe that only one rocker arm is doing this and that the others are ok. After idling for a few seconds it smoothed out and everything sounded ok. Later in the day I started the car again and it did the same thing. It's been a few days now and the car still does this. When it chatters it is very noticeable and after it smooths out it is perfectly quiet. It definitely is not a rod knocking.

The strange thing is that this noise doesn't always happen when I start the engine. It will do it on cold starts as well as hot starts. I can shut the engine off after driving several miles, wait thirty seconds and start it again, and it will chatter for a few seconds and then smooth out and be quiet. I can let it sit awhile or overnight and start it and it may or may not chatter, but it usually does.

The engine is otherwise smooth and is delivering full power with no other symptoms of anything wrong.

I am not a mechanic, but it is my understanding that pushrods are hollow with a hole going up the center for the oil to get to the rocker arm. Is it likely that I have a pushrod that is clogged up? If so, should I run some detergent oil for a while, or dump a can of motorflush into the crankcase and then change the oil? The oil that is currently in the engine is only a couple months old and is perfectly clear and clean.

If I take this to a local mechanic shop, what am I looking at spending to have the pushrod and rocker arm replaced?

Thanks for the help.

Reply to
j
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Did you ever have the hood open when it happens? Might be the idler bearing sticking, which causes the idler arm to jump around. Makes a loud clattering noise. Pretty cheap to fix.

--Vic

Reply to
Vic Smith

If it is valve noise I would suspect a failing lifter before a pushrod or rocker arm. Your engine has hydraulic lifters which in very simple terms are hydraulic springs to keep all the slop out of the works. They can fail such that the oil leaks out and they have to "pump back up" once the engine is running and the oil pressure is back up again.

At this point we don't know for sure that it is a valve train problem though... Lots of other things can make ticking noises.

Steve B.

Reply to
Steve B.

Did this happen right after an oil change?

Reply to
Ashton Crusher

No, I changed the oil a couple months ago.

Reply to
j

Take your oil filter off and try a different one. After running the engine, check your oil level and bring it back to full. Make sure your replacement filter is something other than a Fram. Try a Wix.

Reply to
Kruse

Too bad because this seems to happens lot lately to folks that use Fram oil filters.

I actually thought I blew my engine after a hard 4500 mile run and an oil change at the end of it. The start up valve train noise was 'bad', then I remembered about the damn oil filter I got on sale. I forgot about the Bad Fram filters.

Changed the filter out to a generic store brand white one and my engine went back to a purr.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > No, I changed the oil a couple months ago.
Reply to
Mike Romain

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Its not a rocker arm, its a hydraulic lifter that is draining when the engine is stopped. Probably has a piece of grit in the check valve seat, or its finally just worn enough that it leaks down. When you start it back up, it takes a little while to finally pump the lifter back up to normal volume.

Its harmless, but annoying.

Reply to
Steve

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