I just received a set of "within spec" used Mahle cylinders and pistons that were alledgedly from a low mile Euro engine. 5 of the cylinders are marked within the triangle 5. One is marked 4. Four of the cylinders have a black residue around the base of the cylinder. Not sure what this is, but I never heard of using any sealer at the base of a turbo cylinder. Also the top surface is "rough" on one cylinder with what I would call gouges and would probably need to be machined. If one cylinder is machined on the top surface will that cause any problem? I'm talking a few thousands. Still in the process of measuring the ovality, taper and piston diameter. The height 5 and 4 measure only 1 or 2 thousands difference. Obviously these were not the original factory installation in my view. What do you guys think? Send them back? or Work with them?

 

A follow up. The 4 cylinders with the sealer on the base all have a small groove in the contact flat. The other 2 do not have the groove. Was this a modification to improve the seal at this point? On closer measurement the cylinder marked with a 4 is within .001 of the others. How much variation can one have on the same side of the engine? If I need to machine the gouged cylinder obviously I will have to match it with the other 2 cylinders. Should I consider having all machined for a ring seal to the head? Or as stated above "work with them or return them"?

 

Second follow up. I found that the 4 cylinders with the groove on the bottom flat are from a 964 Turbo. Not sure about the Height Group 4 cylinder as far as I can find only Group 5 or 6 were ever used. Sending them back and probably buy a new set of Mahle P&C's.