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Old 31st January 2020, 14:15   #71
drjonts
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Default So that is what the bung is for!

OK...so armed with mirror (thanks to the missus), torch and Mk1 eyeball, I popped out to the car, located the bung and had a gander.

It would appear that the tensioner piston is just about fully compressed and has hardly moved since being re-set at the cambelt service 24k miles ago. I think I can see that the locking holes are just about still aligned.

Question...is it possible to install a replacement tensioner wheel so that when bolted to the block it is pinched tight, therefore cannot rotate and will simply keep the piston compressed? Or is it impossible to do that with the design of the bolt / attachment? Just thinking of scenarios. UPDATE: I think Gary (Lovel) has experienced the binding of a non-branded tensioner owing to the thrust washer / spacer tube sizing. See HERE

Otherwise it looks like the piston is not doing its job of taking up the slack on the belt. From the surface appearance (i.e. general / light reddish brown surface rust I think the hydraulic tensioner is the original and wasn't replaced at service.

If I am correct, then that means there is nothing to chase on parts/warranty as the usual recommendation is 100k miles for the tensioner...but as Gary said, the unit can simply be weak / failing and not doing the job.

I will snap some pictures of what the mirror reflection yielded in case it is useful to everyone. The bung obviously allows inspection of the tensioner position so that assessment can be made of what is happening.

Onward with the diagnosis!

Jonty

Last edited by drjonts; 3rd February 2020 at 00:25..
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Old 31st January 2020, 18:02   #72
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Hi Jonty, It certainly sounds like you have similar noisy issues as I had, also my timing belt kit had also been replaced 25,000 miles previously, that's if we can believe the previous garage had actually replaced all the parts.

It does sound like your tensioner is not keeping the belt tight, the slapping/ knocking noise is a sure give away. I understand the hydraulic tensioner rarely fails, but some people like to replace and others don't, mine was not replaced and thankfully all is well over 3 years later.

Will you do a complete belt kit change? I dont think its possible to just replace the belt tensioner with all parts in situ.
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Old 31st January 2020, 18:43   #73
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Cheers Wes.

Will keep you posted here on what I find in case it is useful info. for future members.

If I end up getting right in there I suspect a front belt and all the moving parts will get done...even if I save the rear belts for another time!

Cheers,

Jonty
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Old 2nd February 2020, 17:56   #74
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Default Pictures

Hi folks,

Update: I didn't have much time before the rain came the other day and I thought while the engine was cold and the belt 'slack' I would see what I could do as a test tweak to the cambelt tension. As it looked like the tensioner piston really hadn't shifted in 23k miles, I thought...why not see if anything can move in there.

So I got my little 3/8" ratchet and a flat screwdriver bit together, a mirror lodged beneath the area of interest at an angle and a torch on a magnet, I set about attempting to get the flat of the screwdriver bit into the small gap between tensioner piston body and the pulley carrier. After a lot of tries (mainly of course due to moving backwards with the mirror image) the bit was in place and I gingerly pulled on the ratchet handle.

Didn't feel like very much had happened to be honest, but on checking, the belt must have tightened very slightly as I didn't have the same slip back and forth on the cam sprocket. I took another look down at the mirror and tried to convince myself that a tiny shift had taken place and perhaps I couldn't now see alignment of the pin holes in piston and tensioner body. Perhaps this had moved a mm or 2?

Had forgotten to snap a before picture but managed to get a set up to snap what I could see now.




These show the position after things moved a tiny bit - there was less of the piston showing before I tweaked things when the locking pin holes looked to be still aligned.

Bit the bullet today and started the car up. No obvious flapping from cold on the run between cam sprocket and waterpump and no obvious 'tight belt' noises. Left it running for a bit and things seem OK. Will repeat a few cold starts and see if the piston stays where it is rather than being pushed back on cooling. When happy I'll put the cover back on and try o keep an eye and an ear on it.

Fingers crossed I may have saved the belt from running slack and doing any potential damage. I can keep an eye on things for a bit and hopefully extend the lifetime of everything until the time is better for a belt change. Obviously I can't check the pulley wheels and I still have a feeling that something is 'jammed' enough to not move under the piston action - either the piston itself is stuck or weak or the pulley carrier is stiff (having also found Gary's (Lovel) post about a binding pivot).

Cheers for now.

Jonty

Last edited by drjonts; 3rd February 2020 at 00:27..
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Old 2nd February 2020, 23:32   #75
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Final thought for the night...could the tensioner pulley/idler wheel bolt be slightly loose and allowing the wheel position to rotate back in over a long time thus releasing belt tension? That could explain it partly but the tensioner piston would, I assume, have moved out a bit in sympathy?

My brain says monitor with the knowledge that eventually something more will need doing no doubt. I still feel something is binding and not allowing the tensioner to operate freely.

Jonty

Last edited by drjonts; 3rd February 2020 at 00:21..
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Old 3rd February 2020, 16:53   #76
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Quote:
Originally Posted by drjonts View Post
...could the tensioner pulley/idler wheel bolt be slightly loose and allowing the wheel position to rotate back in over a long time thus releasing belt tension?
Jonty
Yes , I have seen this happen . Probably where people have believed the idler wheel bolt to come ready tightened ; I too have read early instructions which say this bolt must not be disturbed as it is preset in position
If it is loose , the idler wheel then moves back until it rubs on its backplate , loosening the tension .
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Old 3rd February 2020, 17:47   #77
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... am I to assume that I have to accept that it's all going to have to be done again after just 25ish thousand miles?
Hello Jonty,

I've just read your story and I would say that the answer to your question is yes. Setting up the tensioner pulley according to the INA instructions is essential and the garage which worked upon it last probably did not have access to those instructions. You have though.

Simon
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Old 3rd February 2020, 17:50   #78
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Thanks Chris - I guess I have a worry that this could be the issue. If that is the case then there will be no question about what I will need to do. At the minimum it would be take everything off the front and at least renew the tensioner idler and piston...without disturbing the timing!

But, I am back to head scratching today...cold start and the belt seemed to have gone back to flapping . Stopped the engine without it warming up and felt the belt...a bit slack again.

So I will get the mirror and torch out and have another look at the tensioner piston. If it has retreated once again then I assume that the spring is weak and unable to overcome the force required to tension the belt.

Will keep everyone posted.


Jonty

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Old 3rd February 2020, 18:01   #79
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Cheers Simon.

I have indeed learned a few gems along the diagnosis journey and when I got the car from my Dad-in-Law and there was the sound of a failing pulley somewhere I didn't want to risk doing a belt change myself.

I'm normally OK with the spanners and it's a case of being methodical and following the salient advice on the forum and in the Haynes manual. As pennies are a bit tight I am not sure there is much point in considering getting this sorted on some sort of warranty basis after 4 years and the mileage as it could be the tensioner piston yet, so I might just pop the car on the drive for a bit and set to the task.

Would anyone have any experience of the cut price timing tool sets that have become available (about £50)?

Cheers,

Jonty

BTW...anyone any experience of X350 XJ8 Jags? I was wondering what a 4.2 V8 would be like?
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Old 3rd February 2020, 18:05   #80
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Originally Posted by drjonts View Post
... at least renew the tensioner idler and piston...without disturbing the timing!
You'll need the service tools to prevent the timing being lost. Please note though that the tensioner pulley won't need renewing unless its bearings are shot. Your problem appears to be that it hasn't been set-up properly. The "piston" is very unlikely to be faulty as Trikey has said (mine wasn't and it's nearly 20 years old and 100,000 miles).
Quote:
Originally Posted by drjonts View Post
... I assume that the spring is weak and unable to overcome the force required to tension the belt.
There is no spring, the tensioner is hydraulic and its associated pulley needs setting-up according to the INA instructions.

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