Thread: 300tdi squeak after timing belt change

Originally Posted by Landi

Just had my timing belt changed on my 300tdi, and after a day of driving it, it has developed a squeaking noise. Doesnt seem to be affected by speed. Does it at idle and on the move. What should i check for?

Does it have aircon?

My D1 has A/C and my squeaky noise(sounds like a trapped bird) is from the A/C belt. Sprayed it with belt grip goop, and goes away for a few miles and then back again.
Going to change the A/C belt, in the hope it goes with the old belt.

Did you change the front main seal, engine block to crankshaft, not the front timing cover seal?
I couldn't work out a way to get the old one out, and greased up the OK looking old one as I fitted the new crank cog .. but paying for it now as it started to leak a short while later!

So now I have to redo it all again to replace the front seal.

if you didn't change the front main seal, you'd know it's leaking as it runs out the drain plug(wading plug hole) and runs along the sump appearing like a sump leak as it smears the sump with oil!


.. live and learn I guess(for me).

Belt Tensioner
Good ol penny trick 10 cents will do the trick
Discovery Penny trick - YouTube

Yeah i have a feeling its the tensioner. Just not sure why its decided to start making the noise now. Looks like its all been put back together correctly. Never heard the noise before gettinf the timing belt done.

Did you do any work other than just the timing belt change?

If you changed the serpentine belt then try the old one back on.

From my experience I've not had a timing belt squeal. Just to check, if you have wading plugs installed, take the timing case one out to see if you get oil, belt fluff or bits of rubber with a wire probe. I find the o-ring on the crank, behind the crank pulley, is a bugger to install. In theory you slide the crank pulley, over the key, toward the waiting o-ring in situ. Under pressure the o-ring is then supposed to bed itself in a seat in the crank pully. Often as not the o-ring does not seat and gets squashed or pinched. I install the o-ring in the pulley before installing the pulley, and work the o-ring over the key as you go.

Check the rubber bonding in your harmonic balancer in case the two halves are separating and making a noise - also check that the crank nose bolt has not worked loose ie not torqued up properly.

I've got 4 disco 1 tdi300s. Three out of four vehicles give no real problem when it comes to belt squeal. Detect the faulty part, replace it, squeal goes.

The fourth vehicle is a right royal pain in the...

It basically has a new viscous fan bearing, new tensioner, new harmonic balancer, new water pump, and new power steering pump. I've even replaced the bearings in new units just in case, but to no good effect. Only the alternator has not been replaced.

Different teeth profiles and rubber formulations on the same belt brand and part number!!!! give different results. So you can no longer rely on ordering a replacement of the same non-squealing belt (that is wearing out) and expect the new one to be equally quiet. In a system not working properly I've found square profile teeth give more squeal than tapered teeth.

Try putting water onto the back of the belt. If the squeal goes then it is more likely to be an alignment problem related to say the tensioner arm than a bearing issue primarily - that's not to say a bearing is not causing the problem, its just not squealing.

Regarding my problematic disco, getting a lever behind the tension arm, when the engine is running, alleviates the noise.

I also noticed that the flange (radiator side) on the viscous fan pully hub, was being polished as the belt came off. Moving the viscous fan bearing forward in the timing cover (toward the radiator rather than the engine) greatly relieves the squeal, but then the belt starts to protrude a couple of mm to the side of the tensioning wheel. Ugghh! I'm beginning to suspect a basic machining flaw in some part of the front of the engine, or belt tensioners are not being made to exacting standards. I get the impression that the tensioner is pushing the belt aside, off track, like pushing a hamock aside between posts.

The tensioner halfs are separated by a teflon disk. In my experience the disk wears thin on the drivers side, remaining near factory thick on the passenger side. This indicates to me that the tensioning arm, under spring pressure, tends to want to point to the front of the vehicle over time. This uneven wear throws the pressure arm on the tensioner out of alignment giving rise to a squeal. Simply replace the tensioner. Have tried several aftermarket tensioners, where the teflon fails very quickly (did they use plastic from an icecream container?). Dayco has given best results.

Would not recommend the coin behind the tensioner. I tried something similar on a tensioner where the teflon had worn unevenly. Solved the squeal for several months. Then the tensioner sheared it's bolt, hitting the airconcompressor taking out one of its mounting threads! The coin removes the ability to bed the tensioner properly to the mounting point, leaving the bolt to take all the stress.

I had a squeaky type noise on the wife's tdi300 Disco. Only really at idle, was the serpentine belt tension pulley bearing seizing up. You can buy a complete unit for about $100 or a bearing for less than $10.

Eventually it started to sound like a whip crack when you reved it up.

At different times we had the tensioner bearing begin to give trouble and run off centre, and also later the air-con pulley seized in the middle of The Simpson (we just disconnected it).