Hi -
I am the original owner of a 1998 V70 GLT (LPT motor), bone stock with no engine performance upgrades. It now has about 250K miles on it and has been meticulously maintained and nothing but Mobil 1 has been used every 5000 miles since new. It has never been abused or overheated.
The engine started developing classic lifter tick so I decided to replace the oil pan o-rings and see if that would quiet it down. There was plenty of oil splashing around in the top end of the engine when running, but the hydraulic lifters are original and the oil pan o-rings had never been changed so I figured I would start with the o-rings.
When I got the oil pan off I found the engine super clean inside, but found chunks of the #2 and #4 piston skirts at the bottom of the pan and smaller pieces of same in the oil intake tube screen. The material is from the lower half inch of the exhaust side of both pistons. The oil was not full of shiny particles so I have no idea how long ago this may have happened.
I had the head reworked at 210K due to burned valves on #3 and #5, and at that time the valve stem seals and three exhaust valves were replaced (the third valve was preventive). The car ran flawlessly for close to 40K miles after that and still does - except for the ticking.
I decided to go ahead and tear the engine down and pull the pistons out. The failure modes of pistons #2 and #4 are identical. I have to rule out traditional piston slap because there is no discernible piston slap markings on the pistons or on the cylinder walls. There is plenty of crosshatch pattern seen on the cylinder walls. There is some minor vertical scoring on some cylinder walls (and I mean minor), which I am guessing is probably from when the valves burned and perhaps generated some small pieces of debris that got trapped between the pistons and the cylinder walls. Or I may have generated some debris when cleaning the carbon off the piston tops at that time.
The rod bearings look fantastic for 250k. There is no wear visible on the crankshaft rod journals. All five bearing sets show almost nil wear. No copper showing except where the bearing halves meet.
Interestingly there are marks on the crankshaft counterweights and the bottom front skirts of pistons 2 and 4 as well. I can only assume that the crank has directly contacted the pistons at both front and rear (with the rear breaking off - or the debris from the piston failure got trapped between pistons and crank counterweights while heading down to the oil pan.
I have only one theory so far. When the valves on #3 and #5 burned 35k miles ago the car had to be driven 500 miles over mountains to get it home. It struggled up the mountains and by the time I got it home it was barely running. Is it possible that the rods on #2 and #4 may have slightly bent as a result of that fateful trip?
I really don't have the ability to easily pull the motor where the car sits, so any words of wisdom with respect to replacing just two pistons and their rings - or should I bite the bullet and have the bottom end rebuilt? I know a used engine might be the cheaper route but I personally don't think its worth dealing with an unknown maintenance history. Something about the "devil you know vs. the devil you don't" - unless someone has a cherry 98 T5 motor sitting in their garage
And I don't really want to start down the path of making the changes needed to have a 99+ motor work. I just recently installed new valve timing components, new PCV and a whole lot more on this one.I'm going to take the piston and connecting rod assemblies to my engine shop and see if they can see any discrepancies with the rods. But meanwhile, has anyone seen this kind of failure before? Any other ideas as to what may have caused it?
It's a lovely car otherwise and in excellent condition. I had no plans on parting with it anytime soon.
High res pictures follow ...
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