2002 S60 2.4 turbo ascertaining correct crank position

Madmartigan9 · Post by **Madmartigan9** » 07 Jul 2014, 06:34

I have recently changed the head gasket and in so doing the crankshaft was possibly rotatated once or twice.Hence,I have bent all 20 valves. I am now having new valves fitted and the head skimmed. Before I re-assemble,how do I know whether the crankshaft is on an exhaust or compression stroke?

draser · Post by **draser** » 08 Jul 2014, 08:37

Need to bring piston #1 to TDC and lign up the mark on pulley to mark on block. Then hand rotate cam shafts to have valves closed for #1 cylinder and align marks as you would for timing belt change. Look at valves and piston locations to make sure they're correct. Then rotate crank 2 full revs and line up marks. Rotate cams 1 full rev and align marks. You should have next piston - based on firing order - at TDC and coresponding valves up. Do that for all 5 making sure that as you have the piston up at TDC the valves are up as well. When you're back to piston #1 and all crank/cam shafts line up to their marks then you can install the head.

Post by **chrism** » 08 Jul 2014, 15:14

When the crank sprocket is set on its timing mark, the engine is NOT exactly at TDC, but rather a few (or maybe several?) degrees off of TDC, thus none of the pistons are all the way at the top of their stroke. This is what some people refer to as the "safe" zone and it is where you want the engine sitting at when you reassemble the head. That way you don't risk valve/piston contact. When you get ready to install the timing belt, double check that the crank is set on its mark (safe position) and CAREFULLY rotate each cam to align with its timing mark. If you feel any internal contact when turning a cam, stop and figure out why. Once the belt is in place and tension applied, check all three marks again. Then rotate the crank at least two revolutions, again being very sensitive to any internal contact. Do all of this without any spark plugs in so that you will be more likely to feel internal contact if it were to occur.

Question: Did you remove either cam sprocket from its cam? If you did then there are a couple additional steps and an alignment tool required to insure correct cam orientation.