Herr Bain, The good news is that you do not have to take the oil pan off to check/replace the relief valve piston. I never took my pan off. I am really happy that I did nót have to take that step. I do not know how many oil pumps came with plastic pistons or when there was a change to metal ones, but I say rather safe than sorry. If you are coming up on a timing belt change, pull the crank pulley and the crank timing belt gear. You will see four Torq head bolts that hold the oil pump in. Remove the bolts and the pump slides straight out. The piston was about $12 and the oil pump kit was about $23 (incl frt seal, oil pump seal, oil pump gasket). If you have a plastic piston in the relief valve you will have to separate the oil pump by removing the back gasket and removing 2 small hex head screws. Push the piston out and put the new one in. That's all. When you get ready to install the oil pump back into the engine you will need a special tool to get the front seal over the crankshaft. I used a thin walled piece of pipe but I think the book called for Volvo tool #5455. It makes the job real easy to get the oil pump back on.

I hope that there are not many of these plastic pistons out there. I feel that something so mission critical should be bulletproof! This engine is way better the the PRV V6's, but for $10k for a new engine there should not be an oil psi relief valve that breaks like this one did!

good luck.