I have a 2000 Kia Sportage that has been seriously overheated twice (that I know of). I got it used with 160k miles. It has 252k miles now. The first time it overheated the head warped. I had it machined and all was good for 2 years. The second time (right now!) I got a reconditioned head. When I pulled the old head I noticed some scoring on the front wall of the #2 cylinder. It's fairly smooth until the very top of the bore, but then it's noticeably rough between the area where the upper compression ring and the oil ring would be at the top of the stroke. In the image that's not glare- it's a different texture. With such high mileage I'm really not wanting to put any more money into repairing the bottom end. Is scoring like this common? What problems might I expect if I leave it like it is?
It looks like the piston is worn and is moving around at the top of the bore. 252k, I would think it is about average.
September, 30, 2012 AT 6:20 PM
The overheating has damaged the piston rings and most likely you would have pistons knocking noise coupled with loss of compression and oil consumption if you are not going to do anything with it.
I would suggest at least to have a look at the piston rings and replace them.
October, 19, 2012 AT 10:09 PM
Well, of course I took the shortcut and just slapped it all back together. A couple of years ago after getting the head shaved because of warping the compression was 90-75-75-90. After putting the reconditioned head on it this time it is 125-75-125-125. My compression gauge is ancient and sticks so the numbers might not be quite right but obviously #2 is low. The car runs better than ever, but smokes like an old mosquito smoke truck. It's all bue oil smoke. It also leaks oil now, which it has never done before. If I start it and just let it idle it will smoke as long as it is running. If I drive it the smoke clears up within a mile or two and doesn't return, even when idling. There is very minor blue smoke after that if I rev it up with no load but not enough to bother me. I've driven it about 60 miles.
I do have a very light tapping sound now. It's barely noticeable with the hood open and not noticeable at all with it shut. Maybe that's the piston tapping?
I don't have any noticeable blowby from the oil dipstick tube, but with the oil filler cap off it sounds like I have an exhaust pipe coming right out the head.
October, 20, 2012 AT 12:21 PM
75 psi is very low as compared to the others. Since you have been running the engine, recheck the compression to see if there are any difference. The smoke is oil burning and it could be from the piston rings or the valve seals.
November, 4, 2012 AT 12:41 AM
I finally had time to work on this again. The #1 and 2 piston rings were fused to the piston. They looked horrible. New pistons and rings are on the way. The rod bearings looked great but I'm replacing them too. I deglazed the cylinders. They look better than I expected now. I'm beginning to see some light at the end of this tunnel!
November, 4, 2012 AT 8:47 AM
I had recommended checking the pistons rings as they can be damaged by overheating.
After this work you should be good for another few more years. Btw since engine is out, ensure you desludge it well and avoid oil treatments at regular oil changes.
November, 13, 2012 AT 12:03 AM
It turns out 3 out of 4 pistons had fused rings. I'm pretty surprised it ran at all like that. I replaced the pistons, rings, wrist pins, and rod bearings this weekend. The engine runs GREAT now. I was pretty apprehensive since this was my first time fooling around with a bottom end but it was really pretty easy- except for getting the oil pan off! I had 145-150 psi on all four cylinders before running it for seating. The way the intake, plugs, and coils go into this engine make it pretty impractical to check it again after running it, but I'm very pleased with the compression numbers. The oil leak appears to have been at the rear of the oil pan. The sealant was thinnest there and it's not leaking now. I guess blow-by caused that leak. I haven't road tested it yet but I'm looking forward to seeing how it performs with good compression. It has been low for years. Thanks for the comments.