406oc.co.uk

Yesterday I replaced the cambelt. Used the excellent guide at http://406oc.co.uk/viewtopic.php?f=10&t=8229&p=79562 Took me 4 hours, including half an hour lunch. Everything went by the book.

However, i now hear a very light whining noise. It is only there when the engine is hot. Only at around 1400-1700 rpm, so not while idling. It cannot be heard when cruising on the motorway. Only when driving slowly at relatively low revs it can be heard. Looking under the bonnet with the engine running and revving a bit, it can be clearly heard that the sound comes from the cambelt area. It is not the drive belt (which was also renewed, btw).

I'm sure it is not the cambelt squealing on a seized (tensioner) pulley. I know that sound, this is way softer.

Googling i came across http://forums.tdiclub.com/showthread.php?t=289928 and http://forums.tdiclub.com/showthread.php?t=312026 . Quote:

"ive done thousands of tdi timing belt jobs and found some do whine especially the gates belts"

By chance, the new belt i bought is a Gates.

Other qoutes:

"You can decrease it by backing off the tensioner somewhat, it will be less loud but still present, you just have to be prepared to readjust the tension intermittently(probably at least once a year"
"the noise is normal - the new Kevlar (in my case Dayco) belts make that noise.".

Does anyone have experience in dealing with this issue? Did anyone loosen the tension? Or should i just accept this and live with it?

Thanks!

Did you slacken the bolts holding the camshaft pulley to the camshaft to allow the tension to equalise on both sides of the belt? If you don't it's common to have too much tension and hence the light whining noise you describe. (The bolts holding the pulley on have slotted holes permitting the pulley to be rotated a few degrees relative to the camshaft).

No, i didn't.... this was one of the steps that was explained in Haynes but not in the mentioned guide. I skipped it, also because i did not understand from Haynes why this had to be done.

So that might very well explain. I will follow up on your suggestion. Thanks very much!

On second thought: i skipped it because the pins went into the timing holes just like that. There was no need for adjustment. I thought releasing the camshaft pulley bolts would only be necessary if it was not possible to put both pins (cam pulley + crank pulley) in simultaneously.

I have had problems with that adjustment, can't quite see the point, the new belt is not going to be that different, I did do it and it ended up against the forward stop but checked the timing and it was spot on.

An over tight belt will whine, I have had this problem and just slackened it off a little. Never had this problem with the XUD.

Peter

Ok, so maybe that is the only issue, that my belt is a bit over tight. I will see if i can loosen it up slightly.

Thanks for the suggestion!

Thanks Doggy, read that. I'm not sure if the cam pulley on my 2.0 has the 3 bolts that jasper is referring to:

jasper5 wrote: ↑ WITH THE LOCKING PINS IN PLACE....slacken off the 3 bolts on the cam pulley then turn the tensioner pulley [...] it's important [...] to allow the cam pulley to be moved whilst the tension is set.

Maybe is the above only applicable to the 2.2 HDI?

I'll have a look as soon as i have some time.

Yes, the slackening of the 3 bolts is related to the 2.2 engine.

Your engine whine is definitely caused by the belt tension being too tight.

Fit a 16mm spanner to the cam pulley and gently tap it to the left so that tension is on the right side of the belt (fuel pump pulley) then get hold of the tensioner pulley and try to turn it by hand without the belt moving...if you can't turn the pulley then the tension is too tight.

Slacken the tensioner pulley nut a fraction and fit a 8mm square bar into the pulley hole and turn it a fraction until you can turn the pulley by hand without it being too easy to turn....it should have resistance against the belt. A 8mm square rod for fitting household door handles is a good tool to use.
I've done at least 70 of these timing belts and this is the best way to tension the belt.

jasper5 wrote: ↑Mon Apr 15, 2019 9:17 am Your engine whine is definitely caused by the belt tension being too tight.

That's a clear statement

I've done at least 70 of these timing belts

Respect! Gives me a lot of confidence.

I appreciate it; will follow up.

auxillary or serpentine belt tension roller bearing makes a similar noise my 406 1.8 16v sounded rough as hell on idle and low revs,changed outthe tensioner and all is quiet as can be now,good luck

Solved! Yesterday evening i took half an hour to check. It was exactly as Jasper said.

Removed the top plastic cover in order to get to the tensioner pulley.Then tapped the cam pulley so that the tension on the belt is tight on the right hand side of the pulley, and a bit looser on the left hand side. Tried to rotate the tensioner pulley by hand: no way, it was too much stuck against the belt. So slackened the bolt and loosened the tension until i could rotate the tensioner pulley by hand (with a little force), then tightened up the bolt. After refitting everyting went for a test drive to warm up the engine and... gone is the whining

So indeed, the whine is caused by the tension being too tight. It has nothing to do with "new Kevlar" materials or whatever.

Thanks again for your support! Cheers!

Glad you managed to fix it

I used to maintain a fleet of 60 2.0 HDI vans and replaced the timing belt kits on each one, plus I've done several 406 and 307 HDI ones, plus a couple of 407s.
I had a couple of tight ones amongst all of the ones I did.
I replaced the timing belt kit for a sadly departed old friend off this forum (Puggy) his old timing belt was very noisy due to a very tight tensioner.
The XUD was never tight as the tensioner was spring loaded and gave automatic tension.

All the best

Sounds you have a lot of knowledge about these motors... If you ever come this direction please PM me, so that i can learn a bit more. And we could turn some whine into wine (or beer or whatever you like)

So its sort or normal but not normal? Is the whining anything to worry about or just irritating? I've just had my cambelt changed at a garage and the engine sounds good and its running ok , but definitely different and also some vibration sound at low revs.