Hello, this is my first post so please forgive me if I am in the wrong category or my question has been asked before, I searched and didn't find anything. I have a stock '91 dx hatch. D15B1 engine. When I bought the car in January, it was in poor condition and I have put around 2000 into restoring it. I had the head rebuilt (valve guides, piston rings, & rod bearings) replaced gaskets, replaced oil pump, starter, alternator, water pump... Basically everything but the block is brand new. The car originally had no exhaust after the catalytic converter, which I got rid of and installed a new exhaust without the cat. I also replaced suspension/brake components, but I have no problems with them. My problem is I took the car on the freeway, which I have done countless times since I had the repairs done and after maybe 15-20 minutes of driving, my car starts blowing thick white smoke from the exhaust. I let off the gas and it stops, but as soon as I try to accelerate, the smoke comes back and it continues to blow until I stop the car and turn it off. It smells like oil burning, which is exactly how it was before I had the repairs done. The problem goes away if I come to a stop and turn the car off for a little bit and then I can accelerate normally back to freeway speed. But again, 20 minutes of 55-60 mph and it starts blowing smoke. Any ideas on what could be going wrong?

 

Since you've replaced a lot of parts that narrows the field quite a bit. About the only thing left in my opinion would be the block. I would perform a compression test and cylinder leak-down test both cold and after running on the highway for awhile.

 

So a damaged block would cause this to happen? The head was rebuilt in February and the problem just started happening today. Wouldn't it have been doing this the whole time if the block was bad?

 

Yes and no.

Yes, if it was always bad it should have always been blowing smoke.

No, there is something that comes to mind. If you have a closed system, for this example your brake lines. And slowly but surely you have a wheel cylinder leaking. It doesn't leak a lot, but it leaks. One day that wheel cylinder gives up and bust open. So you fix the problem by replacing that wheel cylinder. Now it holds pressure 100% and stronger than ever. But now there isn't that leak and there is more pressure on a different wheel cylinder. That wheel cylinder starts to leak and busts.

Now take it from me, that does happen. Happened on a car of mine actually. Your fixed head could cause a problem else where. It's a possibility.

But to me is sounds kind of weird. Only high way speeds you say? Never sooner? That will take some investigation. Warming it up to blow smoke and then removing a spark plug to do a cylinder compression test sounds like a bad idea to me. First off, everything is hot which isn't really good for your hands. But more importantly, everything is hot. Hot aluminum is known to change shapes. Which is why you don't remove a head on a hot motor. If you remove the spark plug the aluminum may warp. Not saying it will, but it could.