Anyone with BAD piston slap/oil consumption....
02-14-2004, 02:39 AM
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Anyone with BAD piston slap/oil consumption.... I haven't been here in a LONG time, and I have no idea what my old user name was. Now that I actually have something to post I had to make a new login. This is my name on many forums now... so I guess it will work here, too.
So my car has had really bad piston slap (duramax volume when cold, VW rabbit volume when hot) and used excessive oil since I bought it. This has never made me very happy. Last November (at 32,000 miles) I finally took it to the stealership and complained. They said "Holy crap, that thing sounds like a diesel ." I said "Ummm.... yeah, I know." So, after they talked to the big guys at GM, the best they could come up with was replacing all the rings.
Neither myself or the head technician though this would do a bit of good... but his hands were tied. They ordered the rings, and a couple of weeks later they were replaced.
Guess what... no difference. GM said to give it a few weeks and see if it got any better. Of course it didn't.
So, January rolls around and I take it back. Same technician looks at it and talks to GM. GM says this time we can replace the pistons with new pistons, and put the 'larger' pistons in the 'larger' holes. We all know that piston slap comes from an cylinder overbore (and so does GM), so how will this do any good?
I talked to the tech about it, and we were both pissed off about the whole situation (him because he didn't want to tear it apart again, me because it's my damn car). So, I got home and did some reasearch. What I found was interesting, and probably not commonly known: The LS1 only has .001" of tolerance for it's factory bore specification. I called one of my mechanic friends back home and asked him if a .001" over-bore could cause the sound I'm hearing. His response was "F*%k no, man. It'd probably take at least .003" over to get it to sound like that once it warms up."
So, I went back to the dealership a few days later once they had it broken down (heads off, pistons out) and took a look. Sure enough, #1 cylinder had visible scuffing at the bottom of the stroke. Piston slap doesn't effect the engine's reliability, eh? I talked to the tech about the possibility of it the bore being out of spec, and he said if it was, GM would have to buy me a new engine. #1 cylinder bore: 3.900"
This tuesday my new engine showed up at the dealership (with a corvette oil pan installed, oddly enough). They swapped the oil pan and hooked everything else up and.....
ZERO piston slap. It was 45 degrees outside, and not even the slightest noise from a cold start. I can actually HEAR the valvetrain!
Also, my last engine had the little 'bullseye' on the block. This one doesn't, and it's a bit less 'bright' than the other. I haven't checked the number on the back of the block, but I will tommorow. I think I already know what I will find.
Summary: GM sucks. They design a great engine, then skimp on the QA and they let a lot of out of specification engines leave the factory in our cars. Bad piston slap does increase wear on your engine (visibly at 32K miles, I might add). Make them fix their mistake while you still have a warranty, or you will likely be paying for it at 125K miles.
Discuss.
So my car has had really bad piston slap (duramax volume when cold, VW rabbit volume when hot) and used excessive oil since I bought it. This has never made me very happy. Last November (at 32,000 miles) I finally took it to the stealership and complained. They said "Holy crap, that thing sounds like a diesel ." I said "Ummm.... yeah, I know." So, after they talked to the big guys at GM, the best they could come up with was replacing all the rings.
Neither myself or the head technician though this would do a bit of good... but his hands were tied. They ordered the rings, and a couple of weeks later they were replaced.
Guess what... no difference. GM said to give it a few weeks and see if it got any better. Of course it didn't.
So, January rolls around and I take it back. Same technician looks at it and talks to GM. GM says this time we can replace the pistons with new pistons, and put the 'larger' pistons in the 'larger' holes. We all know that piston slap comes from an cylinder overbore (and so does GM), so how will this do any good?
I talked to the tech about it, and we were both pissed off about the whole situation (him because he didn't want to tear it apart again, me because it's my damn car). So, I got home and did some reasearch. What I found was interesting, and probably not commonly known: The LS1 only has .001" of tolerance for it's factory bore specification. I called one of my mechanic friends back home and asked him if a .001" over-bore could cause the sound I'm hearing. His response was "F*%k no, man. It'd probably take at least .003" over to get it to sound like that once it warms up."
So, I went back to the dealership a few days later once they had it broken down (heads off, pistons out) and took a look. Sure enough, #1 cylinder had visible scuffing at the bottom of the stroke. Piston slap doesn't effect the engine's reliability, eh? I talked to the tech about the possibility of it the bore being out of spec, and he said if it was, GM would have to buy me a new engine. #1 cylinder bore: 3.900"
This tuesday my new engine showed up at the dealership (with a corvette oil pan installed, oddly enough). They swapped the oil pan and hooked everything else up and.....
ZERO piston slap. It was 45 degrees outside, and not even the slightest noise from a cold start. I can actually HEAR the valvetrain!
Also, my last engine had the little 'bullseye' on the block. This one doesn't, and it's a bit less 'bright' than the other. I haven't checked the number on the back of the block, but I will tommorow. I think I already know what I will find.
Summary: GM sucks. They design a great engine, then skimp on the QA and they let a lot of out of specification engines leave the factory in our cars. Bad piston slap does increase wear on your engine (visibly at 32K miles, I might add). Make them fix their mistake while you still have a warranty, or you will likely be paying for it at 125K miles.
Discuss.
