Hi all,
I am new here and not quite sure of the protocol in asking questions or engaging really so please bare with me. I bought a 94 Corvette a couple of months ago and am having a few issues with it, probably the worst being a pretty intense oil leak. I have had it looked at once and was told it was probably the transmission pan gasket and it would need replaced (done-and still leaking). I have had a different mechanic, take his time looking underneath it and has deduced it is most likely my intake manifold gasket. So, I have a couple of questions and that is, are manifold gasket leaks a common problem for this kind of car? And secondly, I was quoted a price of $504 to replace the intake manifold gasket as well as an EGR valve, (parts & labor-which I've been told it also needs since it idles rough). Does this sound pretty legit? (this would also include an oil change and added anti-freeze because he said I would lose that during the process).
My Dad has a garage with a lift installed and we have done our fair share of things in it, so I've contemplated trying it ourselves (and already talked to him-and he's on board), but just trying to figure out the best way to go I guess.

Oh, one last thing. I've ALSO been told it could be the rear main seal and even leaking out of the head gasket. My original mechanic absolutely went through and eliminated the rear main seal and he said that while it's possible oil could come out of the head, it would be extremely odd and rare.

Anyway, many thanks in advance for your help!

 

Yes the "china wall" area at the back of the intake manifold is one of the places the LT1 is most likely to leak. I'm not saying that the LT1 is a leaky engine - I'm saying if you have an LT1 that is leaking oil, the rear intake area is a common place. You can tell the difference between a china wall leak and a rear main leak: clean the area well, run the engine and watch for new fluid drips. For the average shadetree mechanic, the rear main is not an easy fix. The china wall is much easier... sounds like you and dad should be able to tackle it together.
Yes the quote sounds legit for the work being done. Be sure to ask that the old parts be returned to you.
Oil coming out of the head gasket would be pretty rare, but oil coming out of the valve cover gasket (top of the head) is fairly common.
Hope this helps you.

 

Awesome. I think that does help me out quite a bit. I personally thought that the figure for the work seemed fair as well, but I think I'll probably get together with my Dad and tear into it. While not a licensed mechanic, he's been in the car business (sales, salvage yard, auto-body, mechanic) since the mid 90's so he's pretty good with stuff. (plus it's a good excuse to hang out with him and drink a couple of cold ones!)... Thanks a bunch!

 

The intake is not too bad a job and it is a common source of an oil leak. The LT1/4 engines don't have coolant through the intake manifold, so it is a dry job. (although the throttle body has coolant, it can usually be moved without disconnecting or a big leak.)

The egr valve is also pretty easy. It is located at the rear of the intake and especially if you remove the intake it is a couple minute job to change it.

To me (and I am cheap) I would balk at the $500. The intake gasket and egr can be had for under $50 and can be installed in a few hours with normal hand tools.

And..

Welcome to the forum.

We like pictures. You should show us your car and tell us some about it. I like '94's. I had two. (an admiral blue and a white)

Good luck.

 

Hi QCVette,
Thanks for the response. I think we have decided to just work on it ourselves. We're pretty confident we can handle it now. Eh, the car needs a bit of work even outside of that. It's black, grey interior, 146k miles, with 96 year wheels on it. The interior needs work (seats), but I'll get it looking good eventually. I've had a 73, 90 ZR1 and another 94 back in the day, but those were investments in the car biz, and never one that I intended to keep, so I like having one (now that I'm no longer in the car sales biz) that I can keep.

Thanks again

 

So .... First off - Welcome to the Forum !!!

Ad far as the oil leak goes - Yes any SBC may tend to have issue with leaking from the rear of the block (a.k.a. The China wall). Doing new Intake manifold gaskets, and resealing the ends of the manifold is not too bad a job - it will probably take you a solid morning to pull the intake and most of - if not all afternoon - to do the cleaning and replacing of the parts you removed in the morning, but nothing too too terribly hard or complex to do.

However - you might just want to invest in a bottle of leak check dye to verify that is the problem before you start spinning wrenches. Leak Check dye is dye that you put in the oil that will fluoresce under a black light. So - get some brake clean - spray off the back of the motor to clean the accumulated crud off, pour the leak check dye into the oil and run the car for a little while. Then at night look at the back of the engine compartment with a blacklight (typically available on Ama*** or at a hobby shop). If it's the intake seal - you will see the area around the back of the motor fluorescing like crazy - if it's the rear main seal - you see the fluorescing - but only in the areas that the oil ran down. That should verify where your leak is before you spin any wrenches...

The leak check dye is typically available at better oil parts stores or on-line.... A few oz should cost less than $10.


GOOD LUCK !!!!

 

Welcome

Here's a photo of mine with the intake off, the China Wall is the area at the top and bottom of the photo. I happen to use The Right Stuff to seal the area. Would strongly recommend you get a Factory Service Manual (FSM) for your 94, these can be found on eBay and sometime here on the forum.
Don't forget to ask for help if you get stuck with something, everyone hear is a great source of help.

 

Nice looking car.

I agree with jph46 that the FSM is a good investment. The printed versions can cost quite a bit, but there are also CD versions that are the same thing except in an electronic .pdf format. Rock Auto has them for $22.99. I got one for my '96 and it is a scan of the printed manual with every page and illustration. Although I like the printed versions better, they are usually about $100 used.