Anyone replaced their drive belts themselves?

[Tangent]

I'm at 60k miles which seems to be the recommended belt change interval since the S55 suffers from the same affliction as a few other BMW engines where it can suck a broken drive belt into the crank case. I always DIY but looking up the procedure for replacing the water pump belt looks weird enough I'd like to get some feedback from anyone that's done it.

The alternator belt looks pretty straightforward with the usual type of tensioner but the water pump belt tensioner looks really weird and the procedure seems unclear. It talks about rotating the engine to de-energize the belt pulley, removing screws, and then continuing to rotate the engine until the belt goes slack with a sudden and loud noise. You then replace the belt and rotate the engine in the same direction to tighten the belt so you can tighten the screws again. I don't get it; how does rotating the engine in the same direction both loosen and tighten the belt? Between this and the apparent need to remove the fan cowl which needs the removal of the pump for the charge air cooler I'm really hoping there's a better way to do this than the factory method...

[Tangent]

For anyone going to do this in the future it's actually pretty straightforward once you see it. The hardest part is getting the cooling fan out of the way but the good news is you'll at least be able to clean off your oil cooler; mine had an impressive amount of debris on it.

So the water pump pulley has a slot that the center nut is in. When you remove the 4 10mm bolts around it the pulley can slide in that slot. So first you have to rotate the engine with a 22mm socket on the crank pulley so the visible part of the slot is facing the crank pulley. That way when you remove those 4 bolts it won't be able to slide. With the bolts removed you then rotate the engine again. Once the WP pulley has moved enough it'll slide in that slot to be closer to the crank pulley. Apparently it can do this pretty suddenly and loudly though it didn't for me. Replace the belt and then rotate the pulley again so it slides to the other side of the slot again which has the belt pulled tight and allows reinstallation of the bolts

Edit - visible slot *toward* pulley, not away.

[wangboy925]

No DIY thread on this with pictures or video?

[Tangent]

I was thinking about doing a video but it was a 110 degree day and I just didn't feel up to dealing with messing with the camera while doing all the work as well lol. Follow these instructions all the way until they actually remove crank pulley bolts; you don't need to do that. Then see these directions for reference on doing the water pump belt. The alternator belt is the standard piece of cake using a T60 torx in the tensioner; see these instructions as a reference for the belt routing. If I have a slow work day coming up I might compile this into a single instruction set but this will give you everything you need.

[jwt67]

I am thinking about replacing these belts. I have one question. How do you rotate the crankshaft with a DCT?

[Tangent]

When in park only the transmission is held in place by a parking pawl, the engine will still rotate when you use that 22mm socket on the crank pulley. Mine is a DCT and there was no issue there.

[jwt67]

Originally Posted by Tangent

When in park only the transmission is held in place by a parking pawl, the engine will still rotate when you use that 22mm socket on the crank pulley. Mine is a DCT and there was no issue there.

Thank you!!

[andrei.m4]

Originally Posted by jwt67

I am thinking about replacing these belts. I have one question. How do you rotate the crankshaft with a DCT?

when dct car is stopped no oil pressure to the clutches this mean clutch slip. The only thing hold your car on park is a mechanism in the gearbox close to the driveshaft.