C5 X7 aux belt tensioner.

[Peter.N.]

Hi folks

My latest C5 is playing up ( my first Exclusive). The aux belt tensioner is rattling and jumping about at tick over, above 1000 rpm its fine. I have changed the tensioner, crankshaft pulley and belt with a little difference but not much. The alternator and aircon pulleys appear to be running straight and there is no play in the bearings, the belt is running in its correct position.

Can anyone help?

Thanks

Peter.

[mickthemaverick]

When you say jumping about Peter do you mean in line with the belt or across the belt? If inline it suggests something not happy to rotate at low revs and my shot in the dark would be the aircon compressor clutch, as you have already replaced the crank pulley -

[Peter.N.]

Hi Mick. Its jumping up and down until you increase the revs and then it runs perfectly. I have had this problem before but cant remember what it was, I suspect the crankshaft pulley. The aircon pully appears to be running straight, I even rested a piece of stiff wire on it when rotating and could feel any untoward movement. Is the compressor clutch detachable from the pump?

Thanks

Peter.

[mickthemaverick]

Yes I believe so, it was on my Mk1. If the clutch has got notchy it could cause the jumping. Try having it jumping and then turn the aircon on and off to see if there is any difference before digging deeper.

[Peter.N.]

That Idea had just occurred to me prior to your reply! I will try it and let you know.

Peter

[Peter.N.]

You were right Mick, Put aircon on, nothing happened for a few seconds, then clonk -rattle - rattle. I will have to see if I can get the one of the car in the field. I have five here now including the scrap one. There is a 2010 Exclusive on Ebay for about £200 at the moment, needs new struts, MOT just run out - silly man.

Peter

[mickthemaverick]

Hopefully that will sort it then Peter, another notch on the flagpole

[Peter.N.]

Yep, if the clutch comes off, I don't want to take the pump off if I can help it as the aircon works!

Peter

[mickthemaverick]

This will give you an idea and I did mine in situ without having to drain down.

[Peter.N.]

Thanks Mick. How is it held on? does it have a bolt in the centre?

[mickthemaverick]

Yes 10mm iirc, pretty tight and you have to lock the pulley.. Be careful of any shims between the clutch and the pump. Necessary to give the correct running clearance. Your problem may be that a shim has broken away.

[Lenny]

Have you looked at the alternator clutch pulley?
My money would be on that as mine had exactly these symptoms when mine had given up the ghost.
A new one was about £25 (and another £25 for the tool to remove it).

[Peter.N.]

Thanks Mick. I had a look at a new clutch on Ebay, that showed me how it was fitted.

Lenny. Yes I noticed that has a one way clutch as well but I am pretty sure it is the pump clutch as the noise increased considerably when I switched the aircon on. I have had a number of these cars but have never had this trouble before. I have the rest of the new spheres to fit now and suspension drop links.

Peter

[Peter.N.]

Hi Mick.

Attempted to get the pump pully off but presumably when disengaged the thread is on the pump shaft as it goes round, I take it that it is only locked to the pully when engaged, it won't engage until the engines is running which make it a bit difficult to work on, do you know if there is any way lock the shaft to facilitate removing the nut?

I tried something else today, connect the load tester across the battery which draws 100 - 200 amps thus loading the alternator, this also considerably increased the rattle, this obviously put more load on the belt but I just wondered if the alternator could be the problem - instead of or as well as the pump pully?

Peter

[mickthemaverick]

Hi Peter,
I cannot remember myself from when I did mine but if you look at the video I posted, at around 55 seconds you will see it looks like he inserted an allen key into the centre of the shaft and wedged it on the bench to undo the nut. I imagine it can be done with the right allen key bit in a hex socket and long bar while in situ as I did.

As for the new test it does throw up a new theory in my mind. Allow me to think out loud: Originally you said the problem was the tensioner jumping up and down at low revs, by loading the belt with the a/c on it increased the problem, now by loading the belt with heavier demand from the alternator you have the same situation. It leads me to wonder if the tensioner actually has a strong enough spring in the first place, does it allow itself to be pulled in a bit before it has sufficient strength to hold the belt steady? and then release a tad as the load reduces or the input power increases from the crankshaft as you up the revs? Leads me to wonder if the tensioner you fitted is up to spec, was it an OEM part or an ebay special?