300 Tdi belt tensioner and the dime!

Water on the back of the belt got rid of the chirping noise.

So it would seem it's not bearing noise, nor water pump pulley/belt noise.

The chirping returned once the back of the belt dried.

Interestingly, when I placed a bit of water on the ribbed side, the chirping again stopped. Uggh.

However, the chirp was replaced by a brushing noise akin to a tyre clearing water on the road, and the noise moved to the water pump pulley. The noise was simply the water being squeezed out between the ribs of the belt and ribs of the water pump pulley. Why did it stop the chirping? Just another, less effective way of relieving stress under the tensioner?

I also got rid of the chirp by carefully pushing the tensioner arm (fractions of a mm) toward the engine using a screw driver (akin to the coin effect). Applying downward force on the arm also got rid of the chirp.

Using a breaker bar and 15mm socket I lifted the tensioner up a bit to take some stress off the belt, and got an increase in chirping.

Also ran some 90 grit paper on the tensioner wheel as it rotated, but an increase in matte finish made no difference to the chirp.

Given the vehicle is a post 1996 I also checked I had a 1580 belt on.

Those series of tests indicate to me a new tensioner is in order. That 1 is not doing the job.
Cheers Scott

Unfortunately the one in question is new. Another is on its way. Not really holding my breath that the problem will be solved.

The belt is slipping, but not longitudinally, but across the belt, that is why the coin works.

We need to work out the reason for that, and a more permanent fix.

Quote:

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Originally Posted by workingonit

Unfortunately the one in question is new. Another is on its way. Not really holding my breath that the problem will be solved.

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Ahh, did not know it was new! That is annoying, mine did it so I replaced and it went away, so I assumed the tensioner was cactus. It was at 320k .
Cheers scott

take the belt off wash it in hot dishwashing liquid dry it put it back on
I use the dayco belt should get at least 150,000 from a genuine tensioner
cheers

Tried the belt wash - sorry.

Next! ;)

If replacing the current 'new' tensioner (having filed the protrusion of it) with another new does not work, then I may try tweaking the old 'new' by trying to bent the arm itself more toward the engine to better align the wheel with the belt.

The squeal is gone for the moment. Doing some miles will determine the truth of it.

Recap - squeal coming from under tensioner wheel, relieved by application of water to back of belt.

Took the unbranded old 'new' tensioner off (the one from new, where the hollow centre bolt originally protruded, before I filed it down).

Put the new Dayco tensioner on. Squeak still there, but audibly moved left to where the viscous fan hub resides. Uggghhh.

Application of water to back of belt no longer relieves squealing to any great extent. Water to ribbed side does, momentarily.

Took belt off. Examined ribbing. Noticed lots of polished dots and dashes of rubber caught in the ribs. Clean it all out with scribe tool, then wire brush. Reinstall belt. Squeal still there. The belt is branded Contitech, 1508, made in Croatia.

My understanding is that 1508 length belts are for the later Discos with the smaller alternator pulley. The Disco in question fits that description.

I keep some Contitech 1605 belts for the older Discos I have, with their larger alternator pulley.

I grab one of these new 1605 belts and install it. Low and behold the squeal is gone!

The Contitech 1605 are made in the UK. And the rib pattern is different! The summit of the rib comes to quite a sharp conclusion. Like this ^^^^^^

By comparison the Contitech 1508 ribs conclude as quite a wide plateau. Well, should say 6 of the 7 ribs terminate as a plateau. The rib closest to the engine, looks like it may have worn on the edge, as the summit is more sharp like the 1605, wear possibly being indicated by the belt thread being very visible compared to the edge closest to the radiator, and by comparison to older belts left over from previous services.

Put the old 'new' unbranded tensioner back on, and squeal is still gone :)

Is it just down to rib cross section shape?

My vehicle with the Dayco belt is out and about, so won't see it for a few days. Interesting to see the rib pattern.

Just going out again to start the vehicle up, to enjoy and re-acquaint myself with how the engine should always sound :)

Talcum powder on the belt stops the squeal for months at a time or until you wash the engine or drive through water.

It also makes the engine bay smell nice. :)

Hi guys, I had a problem with my serpentine belt squeaking, and this was my solution.

get a small wire brush, ( steel or HT brass) from autopro etc , about the size of a big tooth brush.

While the engine is running hold it against each pulley in turn to clean the dust etc out of the grooves, ( cranks shaft pulley excepted because of access issues).

Then hold it against the ribbed side of the of the belt to remove dust from the belt ribs and deglaze the belt. it should be good then, it worked for me for a long time. I depends where you drive, if its very dusty you can expect the squeaks to come back, similarly if the belt is old the surface will harden up. ( or get can of "CRC belt grip" in industrial belt cleaner and conditioner)
be careful not to let the brush get caught between the pulley and the belt
Sometime its the tensioner that squeaks because the bearing is dry, the first time it happen i prised the seal off and put some grease in there and put the seal back as a temporary fix. It worked well until i could a new tensioner.

I later punched out the bearing of the old tensioner and fitted anew one and carry it for a spare. cheers simmo