Hello folks, I am new to this forum and figured I would start off with a question... :D I was looking at buying a stock 6 speed 1993 C4 and noticed the exhaust pipes had a copious amount of oily soot in them, more oil than soot. Typically speaking I would think this one is burning way too much oil, which isn't good but as I have never had a Vette before and I am looking to buy my first one I am unaware of some of the foibles intrinsic to the Corvette. My question is this....is this much oil in the exhaust pipe normal? Thank you.

 

Hello and welcome to the forum!

My first instinct would be no, that's not good. However it might not be THAT bad. I would drive it and see how it drives, do a compression and leakdown test on it, etc. It could be as simple as some leaking valve seals.

 

First I would check the oil to make sure they didn't put some Aunt Jemima in there to keep it from smoking, and then have someone else rev the car while you look at the pipes to see if blue smoke comes out the pipes. Have them rev it a few times with a little delay in between. If it passes that test, then maybe it's okay.

Compression tests are somewhat useless because if the oil control rings are bad then the compression rings may seal better because of the oil around them. Of course, if the rings are bad due to cylinder wall wear then the compression test will show that.

But oil in the pipes is not a normal thing, at least not on mine. Dry soot is normal, but not oil.

-Dave C.





[Modified by Dave C. '97 Z28, 5:44 PM 9/4/2003]

 

Is this a high milage car and are the cats still in place? The reason I ask is because if what you find is truly oil at the exhaust tips there is a serious problem. Did the car smoke bad when its driven and I have to assume you test drove the car. I have a bit of soot on the tips of my exhaust as well and sometimes if its started in the morning and with a bit of moisture it does feel "oily" but in fact it isn't.

If it is indeed oil there has to be a lot of it going past the cats that isn't burned, normally even if the car has bad valve seals what would get past the combustion process usually gets burned in the cats. So if it is oil then there is a major problem more so than just valve seals. Also is it just on one side or on both?

Do as the previous post states, perform a cylinder leak down test, and when the plugs are pulled look at them for further signs of oil usage. It is also possible that this was a daily grovery getter that gets driven a few miles and is garaged and maybe the oil wasn't changed as much as needed and the oil rings got fouled.

There is a lot of causes for oil consumption, in any case no its not normal for oil coming out at the tail pipes. I checked out a Ford F350 powerstroke job the other night that came into the shop, the turbo puked its oil seals and thus poured oil into the exhaust system, making a huge mess and talk about smoking!


[Modified by tjwong, 10:11 AM 9/4/2003]

 

Not real high mileage, about 108k, and yes the exhaust is complete. I started the car up and it puffed a little, this was in the afternoon and the ambient temperature was about 90 degrees. The deposits were on both sides of the exhaust also. I was just curious, but it think I will shy away from this one, at $8995 it sounded good but I don't want to do any wrenching just after buying my first Vette. Thanks for the input folks.


[Modified by Shoehorn, 10:48 PM 9/4/2003]