I just picked up a really rough 1999 Yukon for stupid cheap ($500) knowing it had issues. So far before even driving it any further than home I've replaced the radiator as it had a large crack and the power steering pump. I knew about both issues when I bought it. Now its started poring white smoke from the exhaust and idling very rough and at only around 800rpm. It's also before difficult to start. I'm looking for help diagnosing the problem and hopefully fixing it on my own. Forgot to add it has the 5.7L engine with a little over 180k on the odometer.

 

Welcome to the forum.

White smoke from the exhaust generally means coolant is getting in to the cylinders, intake gasket, head gasket, cracked head or block.

 

How would I go about diagnosing which it is? I'm no mechanic, but pretty handy.

 

To get a sure diagnosis you would have to tear the engine apart. With 180k on it, the easiest thing would be put in a new motor, or do a complete rebuild of the one you have.

 

Compression test.


I 2nd the white smoke = coolant is leaving your engine via the exhaust.

If you have cylinders without compression, you're looking at a bad head, head gasket, or worse...

 

Would the common intake manifolds cause this? Just wondering if coolants getting in could come from there as well right?

 

The previous owner said it occasionally would have white smoke coming from the exhaust while idling, but the idling rough and difficulty starting was a recent development. The one time I've test drove it since it did seem to run a bit smoother in the higher RPMs. Since the radiator leak was causing it to go through coolant so fast he had just been using water instead.

Since the compression test seems pretty easy I'll start there Monday and go from there.

 

Lol, I had a 1995 tahoe that would leak coolant from the water pump.

For all summer, I also used just water

 

Funny that you mentioned that. I forgot to mention I just changed the water pump right before it happen. I wonder if that could have something to do with it?

 

I doubt it, even if somehow it was royally messed up, I don't think it would force coolant into the system.

Did you do the compression test?

Does it idle rough, or is it missing any power?