1995 850Turbo Piston Rings After OverHeat?

motoexpedition · Post by **motoexpedition** » 02 Jul 2014, 08:02

Right...
Heater core leak led to a severe overheat. Engine stumbled then died. After which the engine would spin freely without any compression. ( i even took starter in to be rebuilt because i thought it wasnt engaging the flywheel...after re-install, I noticed the crank was indeed spinning.

The plastic ends of the spark cables melted and fused to spark plugs (so difficult to remove) to give an idea of heat. One item to note is the spark plugs where all loose due to overheat apparently...required little to no force to loosen. No compression test done as it was quite obviously pointless.

Head is off with engine in car. Pistons look fine, bores as well though some pistons have more carbon deposits whilst others are clean. I've started removing the oil sump to do a 'dirty' piston ring swap...(unbolt con big end, push through, replace, assemble). Its not an easy job with the engine in...had engine out twice last year, once replace engine and second RMS...I'm not taking it out again. So im looking for excuses to leave the piston rings as is.

The question is...is it likely the piston rings are fine and the loss of compression was somewhere top end or are the rings bad. Heat rises so concentration of heat would have it the head...plus the plugs being loose was an oddity.

Lets have opinions...volvo says replace but then again they also tried to get me to take the car, then to buy their rediculously priced rings...so theres a conflict of interest.

Post by **Ozark Lee** » 02 Jul 2014, 08:11

Normally, if something bad enough happened with the pistons and the rings to cause zero compression, it is visually obvious after you get the head off. It shows up as scored cylinder walls, chunks missing out of the pistons, etc.

...Lee

Post by **rspi** » 02 Jul 2014, 08:16

You should be able to have a shop or someone test the block for damage. It sounds like the head is toast, I would not try to reuse it. Get a replacement.

motoexpedition · Post by **motoexpedition** » 02 Jul 2014, 12:07

I can still see the honing marks in all cylinders...not one score. I thought that was a good sign as well.

Thanks for the posts.