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Calling all ears! So this is my 88 convertible. Just bought this week (knowing about the sounds); towed home and first time letting it run to try to diagnose the sound. It bangs and squeaks and I think it's on the passenger side, maybe top end. But here's the thing; engine starts good enough and the idle is solid. You can hear in the video how it warms up right away and the idle comes down and settles. I even pulled it out of the garage and turned it around to point inward (we backed it in from the tow truck), strong enough that I really had to push on the brakes hard.
I'm wondering if this isn't an engine sound but rather something in the transmission or thereabouts? Maybe that would explain why I had to step hard on the brakes and it seems to pull so hard when in drive.
First step remove drive belt from the accessories to see if noise changes or goes away. (Don't run car long)
Next is to disconnect the transmission from the flex plate, it’s Not a hard thing to do but car needs to be off the ground as much that is Safe.
With car raised remove the Touqe Converter cover and remove the Converter bolts and push the Converter into the transmission to move it away from the plate, start up and listen.
Unfortunately your noise sounds like bottom end so the next step would be pull pan and some bearings I think you have a few spun from the Churp
. You could also pull a quick 1/2 cup oil sample or give a look at dip stick see if it's milky of silver.
Last edited by s carter; Sep 10, 2022 at 02:34 PM.
I'd start with dropping the oil for visual inspection, followed by removing the passenger valve cover. Removing the serpentine belt is a good idea also (^^^mentioned above). I hope you find something minor, but I'm with the above mentioned bottom end....it sounds like the crank thrust/thrust bearing is gone along with main/rod bearing/s. Hopefully you get lucky👍
edit: Just keep thinking about this one....Longshot, broken lifter causing one of the little dog bone lifter keepers to get wedged somehow and one or both of those lifters to rotate sideways and the tin finger that holds the dog bone down scraping on the misaligned mess????....Very interested in diagnosis!
Last edited by '78CorvetteS.A.; Sep 11, 2022 at 04:17 AM.
To my ear, doesn't sound like bearing knock. It's too intermittent. I've not heard bearing knock that isn't a consistent knock determined by rpm. I would add to what has been suggested by saying take the valve covers off to look for issues both static and while briefly running. Sounds to me like something loose bouncing around and getting randomly hit by something. Maybe a baffle or something loose or broke off under the valve cover (maybe a long shot). Hard to say what though.
I have heard many sounds come out of these Engines, and I can agree 89MNvett that you don't condemn until all things checked on knocking. But that Churp is not a happy sound
Removed the accessories belt, that’s not it. Will lift tomorrow and look at trans and then pull the pan. Needs new oil anyway, its black (not milky, no speckles yet).
[edit] …think I’ll start with the top end first and work my way down.
Alrighty then! I almost got the oil pan off. But it won’t clear the cross member; there’s about a half inch clearance.
I’m wondering why others have been able to do this but I can’t. So I called the previous owner, asked a few more questions about the engine and apparently it came from an IROC. Different oil pan?
Update. OK, took a lot of muscle (even broke an extension!) and WD40 to get those bolts off but finally freed the engine from the trans. Ran it; noise is still there.
While I was down there, pulled the pan but doesn’t look like anything’s wrong. No scoring on the bottom half of the cylinders. Rods are tight up and down, side to side. Oil looks and smells old but no flakes or sparkles.
So i started tearing into the top end. Bout half way and I’m pulling out bolts that are filthy (not just stained, I mean grunge).
Then I think back to what the fella told me when I bought it; he said that it’sa rebuilt engine taken from an IROC. Says he had a guy rebuild it. I mentioned the oil and he says that was from break-in and he only drove it 2000 miles before it started to knock. Then he let it sit for a couple years.
Now, I’m not one to accuse lightly, so this is just me trying to figure out what I’m dealt with so I can plan right. But given that I see filth and grunge everywhere, right bolts, and something flopping around in the engine, I’m thinking it’s one of:
the rebuilder was an idiot
the rebuilder lied and the seller was duped
the seller lied… uh, left out some key detail. Yeah.
I'm waiting to hear the Ahha Moment when big problems is found.
It's a little after the fact but have you given the Exhaust a smack with a fist or rubber mallet to see if the catolitic converters haven't fallen apart and are now Rattling around inside the pipes
. Never mind forgot you have the Chirp which is rotation problem
Last edited by s carter; Sep 24, 2022 at 10:17 AM.
Hoping the squeaking isnt a spun bearing.
check the pushrods...may have a lifter issue that can wreak audio havoc.
Hoping you didnt get bs'ed about the rebuild.
If you need a cherry picker you are welcome to make use of mine.
Its light, collapsible not a 200 lb monstrosity
Ill be out of commision for a couple wks...afterwards I could give you a hand perhaps.
Alright, I've got it down to the manifold but have three bolts with stripped star pattern. Some of the bolts came out REAL easy. These three, I tried with a breaker bar but it just stripped them. So going to drill them and back them out with the little reverse-thread thingys (can't remember what they're called... but I have some).
Knockin 'n Squeakin...
