leak in exhaust manifold gasket

[Broslice]

In my '95 celica gt,

Ever heard of a leak in the exhaust manifold gasket allowing oil to burned?

Would the pressure formed in the exhaust cause the vaccum to suck up oil?

[Janaz]

Hello Broslice,

I've just gotten through a long, hard project of dismantling the entire exhaust system for a '95 Mitsubishi Eclipse in order to replace the cat converter and all the exhaust gaskets. So I might be able to help with your question.

Strictly speaking, I don't believe a leak in an exhaust manifold gasket would cause oil to be burned. I think you're getting mixed up here. An exhaust doesn't create vacuum. It allows gases from the combustion in the engine to flow out. If your car is burning oil, most likely it occurs within the engine.

So... is your problem that oil is being burned, or that your gasket is leaking? If you think oil is being burned, what tells you this? And if you think your gasket is leaking, what tells you this? I would answer these questions first.

Hope this helps

[Broslice]

I did a few basic checks... The PCV valve was sucking up oil so I replaced it, solved the problem. I replaced the exhaust manifold gasket as well. However, it looks as though someone messed with it before becuase when i pulled off the nuts, one of the bolts popped off with it and there was some of that metal re-thread stuff on the bolt into the block. It looks like someone cross-threaded it.

What should I do to tightin it down? I've been looking at those helicoil thread repair kits, but they're like 70 bucks. Any suggestions?

[Janaz]

Ok, first of all, if your exhaust manifold can't tighten down all the way, it might leak. So that's a problem. But, fixing the exhaust manifold won't solve the problem of burning oil, if your engine does burn oil.... Anyways, here are some ideas on how to fix the thread on your exhaust manifold to tighten it down.

First of all, check to see if the bolt needs to be replaced. If it's just the bolt that is threaded - and that might be the case - you can buy a new bolt for probably less than a dollar at a hardware store like Ace. Then your problem is fixed cheap. So first of all, I would get a new bolt and see if that works.

If the thread of the actual hole is messed up, this is a little more problematic. There are a number of solutions for fixing a threaded hole. You can buy a heli-coil kit, I know auto parts stores sell them for about 20 or 30 bucks. Personally, I have never used a heli-coil kit, so I don't know how well they work. What I do to fix thread holes is to buy a "tap" at a hardware store. A tap is a special bit that cuts a new thread into a hole, and they usually cost less than 10 dollars. You will need to get a tap that is only a couple of mm larger thread than the hole - MAKE SURE THE TAP IS NOT TOO BIG! Drill out a new thread with the tap, buy a new bolt to fit the new thread, and you can now get the bolt real nice and tight.

[Janaz]

Oh, one more thing: make sure you know how to properly use a tap if you do buy one, ie using cutting oil, being careful, etc. If you don't know how to tap a thread, you could mess up the hole.

[Broslice]

The bolt that I need is 10 mm x 1.25 but the thing is, the next size up is 12 mm x 1.25. That seems like a lot more, and the last thing I want to do is drill too big of a hole. The heli-coil tool is sweet, i just gotta get around to buying one.

As for now, i'm driving around with a missing bolt, and everything is working great. Also, quick question, what do you think caused the leak in the manifold? Back pressure due to catalytic converter? How could I check this? I looked inside when the manifold was off, it looked like a honeycomb, so thats good i suppose...