Question2000 2.4L 4 cylinder engine. The problem started with a leaking water pump. But my friend kept driving the car for two weeks, pulling to the side of the road and putting in water whenever he overheated it. Lots of valve knocking he told me. I put in a new water pump when he brought the car to me, and I test drove it and heard the knocking. When done, started the car and it purred.. for five minutes... then got rough idle, chirping in the valve train, finally quit. It had low power, but sounded good except at idle. I drove it to an expert and he said we probably got the timing belt off a tooth. So I took the covers off and checked marks, they were perfect. Checked two times. Compression test: should be 170psi minimum. #1:140, #2:125, #3:105, #4:130. Was hard to start, so I pulled plugs, they were covered in oil. Replaced plugs and it started after lots of cranking. Purred.. for five minutes. Finally pulled dip stick. Oil in water, water in oil! Blown head gasket! Ok.. So I pulled the head and its not cracked, slight warpage, I will get it resurfaced at machine shop. Finally, here is my question: There is water on top of the pistons. The cylinder walls are covered in rust spots. I don't want to pull the engine. Should I? If not, what should I do about cleaning/honing the cylinder walls? Do you think the crankshaft bearings will be ok? Is there any way to test this with the engine in the car? Can I risk doing the top end and then just changing the oil immediately a few times to clean out the bottom end?
AnswerHi Chris,
My inclination would be to simply clean up the gasket mating surface on the block, and do the same thing with the cylinder walls/piston top surfaces; just enough polishing with very fine emory cloth to clean the surfaces without doing any other grinding. Then make sure that you don't leave any grit. Because you didn't hear any bearing noises so far I would believe that you may have gotten to the problem before any damage to the bottom end occured. Yes, drain oil, fill and drive a bit, then change the oil once, and then see how it goes from there. I believe in leaving well enough alone on the theory that I might just cause unnecessary damage when nothing needed to be done.
Roland
PS: Thanks for the kind evaluation and comments. Because the compression values were within +/- 25% of oneanother, and as far as the minimum is concerned that would not be relevant unless you had a chance to do the readings promptly and with the engine fully warmed up, a fully charged battery to assure required cranking speed, and the throttle wide open. I suspect that they will be significantly higher all the way around after it is reassembled and tested as described. Therefore I would go ahead and put it back together. This history is not so atypical of a blown head gasket as to go any further, and besides the top end and bottom end are quite separate procedures.
