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Old 13th August 2021, 20:20   #1
Shapfell
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Default 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....
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2004 Conn SE 1.8
Work so far:-
Gerry T, Rad Fan Resistor, Handbrake Compensator, Bonnet Catch Block, Leather Handbrake gaiter, Journey Camera,
Sean's DD Unit with Freeview!, Towbar, Rear Sunblind, Smiley!, Headlamp Protectors, Alloy Intake, R75 Brolly, Puddle lights, reversing camera.


2006 MG ZTT 160+ cdti auto; for disposal.


2004 Connie CDTi Tourer; replacement for the ZTT.

Last edited by Shapfell; 13th August 2021 at 20:25..
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Old 13th August 2021, 21:06   #2
Mike Noc
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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.
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Old 14th August 2021, 10:58   #3
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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.
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Old 14th August 2021, 12:13   #4
Shapfell
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Originally Posted by RogerHeinz57 View Post
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.
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2004 Conn SE 1.8
Work so far:-
Gerry T, Rad Fan Resistor, Handbrake Compensator, Bonnet Catch Block, Leather Handbrake gaiter, Journey Camera,
Sean's DD Unit with Freeview!, Towbar, Rear Sunblind, Smiley!, Headlamp Protectors, Alloy Intake, R75 Brolly, Puddle lights, reversing camera.


2006 MG ZTT 160+ cdti auto; for disposal.


2004 Connie CDTi Tourer; replacement for the ZTT.
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Old 15th August 2021, 13:06   #5
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Quote:
Originally Posted by RogerHeinz57 View Post
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.
I believe that when the bolt is being tightened that no loading goes through the rubber damper.-----

Be most unwise if it did.---
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Old 15th August 2021, 13:15   #6
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Quote:
Originally Posted by Shapfell View Post
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.
If it was flapping about with the old belt and doing the same with the new belt then more than likely the belt can be discounted as the problem.

It sounds that there is an intermittent load being applied to the the belt to make it flap.---( ie. Both belts. ) Are you sure as well that the tensioner is working correctly ??---That a steady load is being applied to the belt all the time ??

It could be that one of the other items that's being driver by the belt is close to seizure.--Idler roller, alternator etc.
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Old 16th August 2021, 11:44   #7
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If it was flapping about with the old belt and doing the same with the new belt then more than likely the belt can be discounted as the problem.

It sounds that there is an intermittent load being applied to the the belt to make it flap.---( ie. Both belts. ) Are you sure as well that the tensioner is working correctly ??---That a steady load is being applied to the belt all the time ??

It could be that one of the other items that's being driver by the belt is close to seizure.--Idler roller, alternator etc.

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..
__________________
Oh well, it's only money......

2004 Conn SE 1.8
Work so far:-
Gerry T, Rad Fan Resistor, Handbrake Compensator, Bonnet Catch Block, Leather Handbrake gaiter, Journey Camera,
Sean's DD Unit with Freeview!, Towbar, Rear Sunblind, Smiley!, Headlamp Protectors, Alloy Intake, R75 Brolly, Puddle lights, reversing camera.


2006 MG ZTT 160+ cdti auto; for disposal.


2004 Connie CDTi Tourer; replacement for the ZTT.
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Old 16th August 2021, 12:45   #8
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Quote:
Originally Posted by Shapfell View Post
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!
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Old 16th August 2021, 15:29   #9
Shapfell
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Originally Posted by trikey View Post
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'??
__________________
Oh well, it's only money......

2004 Conn SE 1.8
Work so far:-
Gerry T, Rad Fan Resistor, Handbrake Compensator, Bonnet Catch Block, Leather Handbrake gaiter, Journey Camera,
Sean's DD Unit with Freeview!, Towbar, Rear Sunblind, Smiley!, Headlamp Protectors, Alloy Intake, R75 Brolly, Puddle lights, reversing camera.


2006 MG ZTT 160+ cdti auto; for disposal.


2004 Connie CDTi Tourer; replacement for the ZTT.
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