Cdti Aux Belt slap
 

I'm running out of ideas so I thought I'd lob this to the hive mind on here. My ZTT had the crank pulley dismantle itself, so I bought a reputable one and after having to get a mega-powerful rattler to remove it (thanks Trikey!), I changed it over. Then it fell off. So after checking everything over again, it was refitted and tightened up to effin tight and marked for movement.

Since this was done, the 'pull' side of the drive belt (from the alternator) slaps around madly at idle. So far, I have changed the water pump (last year), idler, tensioner (pulley and tensioner unit), alternator (after it literally blew up on me) and belt. The only bit left is the PS pump but that has no play and the bearings sound good.
Why would the 'pull' side of the belt do this? Ive even had a DTI on the crank pulley and it is concentric (just in case). at a loss now. any ideas??


PS; I found using a cheap ratchet strap through the end ring of a 24mm combo spanner, then around the engine mount works better than amputating bits of hand regularly for the tensioner....

What make of crank pulley? Assuming the engine is idling steadily, and seeing as you have changed just about everything else, then maybe the rubber compound in the pulley is too soft and causing the belt to flap about?

If you can get the car on a T4 you can check the injector compensation at idle to make sure the engine is idling as it should do.

If the pulley has parted company from the engine once already, and simply put back on with more grunt, perhaps some damage has taken place to the structure of the damper inside the pulley, also if the bolt has been used before, there is no guarantee that this will ever work properly. Always a pulley and bolt together new.

Good point. The problem was, the belt was slapping about before the alternator went pop, which was before the pulley came off. I've DTI'd it for concentricity and its OK, so maybe it has got an internal problem. It was one of DMGRS ones so it should be OK.

The only part left that hasn't been changed (Crank pulley, idler, tensioner and tensioning block, water pump, alternator, belt) is the PS pump. Maybe that has started to play up. I may put another on to try it. One thing that did make me think a bit, was when I first had this car the idle was about 900-1000rpm. I found a woodscrew through the throttle pedal holding the revs up but when I removed it, I could find no reason for it being there. But, now if I hold 900rpm, the belt slap stops. Hmmm..

I can adjust the idle via T4 should you wish Mike, you need to find the issue though!

Cheers, I'll give you a shout. It does make me wonder if this has been a problem in the past that eventually 'wore itself in'??