300TDi alternator pulley & serp belt noises

[Countax]

Been getting some strange noises on startup from the front end of my 300Tdi recently and diagnosed it down to the serpentine belt. Many years ago i sorted out the chirping sounds from the belt by putting a shim behind the tensioner to re align the pulleys. But the new noise was only for a short period on cold start up in the morning or if the belt got wet. Going back to the Gates technical page for advice it seems a noisey belt when wet indicates a lack of tension and i have to admit that since i fitted a new alternator a few months ago the tensioner always did look as if it was pushing down too far. Luckily i kept the old pulley off the old alternator and it is clearly larger than the one off the replacement alternator ( approx 60 odd mm verses 49mm dia ) so that confirms the belt tensioner is having to work harded than it should be. My guess is the rev counter is also reading high now because its driven off the alternator which will be spinning faster due to smaller dia pulley.

So if anyone has to replace their alternator i suggest you remove and keep the pulley as it seems all aftermarket ones have the smaller pulley and this might eventually give you the serpentine belt noises i have been getting, which i have to say sound as if something serious inside the engine is breaking up.

Nigel

[cress]

Hi, I have just changed my alternator due to breaking up bearings. the sound off that was quite horific. The alternator was still funtioning, sounded like the rear bearing/ bush was collapsing. Must admit I never checked the size of the pulley, I will do that asap.

I also have a noise from the jockey pulley bearing on the power steering belt. I have re-greased it a couple of times, but replacement is iminent.

Ivan

[BogMonster]

Early vehicles up to about the beginning of 96MY have the 61mm alternator pulley and use belt ERR3287 or PQS000030 for the non squeak version. Later vehicles 96 onwards have a 49mm alternator pulley and ERR5911/PQS000040 belt which is a different length. I believe the change was to make the alternator spin faster and improve charging at idle but it does affect the rev counter as noted.

[Countax]

Early vehicles up to about the beginning of 96MY have the 61mm alternator pulley and use belt ERR3287 or PQS000030 for the non squeak version. Later vehicles 96 onwards have a 49mm alternator pulley and ERR5911/PQS000040 belt which is a different length. I believe the change was to make the alternator spin faster and improve charging at idle but it does affect the rev counter as noted.

Do you know the belt lengths for the versions mentioned above? originally i was using a 1600 length belt, currently it has a 1595 length one fitted and i have heard of people using a 1575 length belt.

Nigel

[BogMonster]

Yep

Just checked the stock downstairs:

PQS000030 is a 7PK1595 for the big alt pulley

ERR5911/PQS000040 is a 7PK1580 for the small alt pulley

+/- 5mm should cause no problems IMHO.

[Countax]

Yep

Just checked the stock downstairs:

PQS000030 is a 7PK1595 for the big alt pulley

ERR5911/PQS000040 is a 7PK1580 for the small alt pulley

+/- 5mm should cause no problems IMHO.

Thx, That was fast. Are you having a competition with Ralf ( Western ) by any chance to see who can come back with the answer fastest

Nigel

[BogMonster]

Thx, That was fast. Are you having a competition with Ralf ( Western ) by any chance to see who can come back with the answer fastest

Nigel

No, I just happen to have a parts shelf with a pile of each about 20 paces from my office PC so it did not take long to find out

[Peter]

Thought I'd let you know how I get rid of my squeaking noises from my 300tdi belt.

Not sure why this works anyway have found it works for me. Take the belt off - very easy on a 300tdi, just got to lever the tensioner back. Turn belt inside out, then with a small flathead screwdriver a good light source, track round the grooves - okay take a while but is quite therapeutic after a while, esp if on back and its sunny.

Every so ofter you'll come to a inbedded piece of what looks like black carbon about the size of a grain of sugar, carefully prise it out with the screwdriver, then carry onto the next one. When clean put belt back on - hey presto no more squeaks.

Of course, if you have a dead bearing in your tensioner, this won't help - but its worth a try.

I reckon this causes the belt to slip slightly and squeak. Give the pulleys a quick rub over with a wire brush, whilst belt is off too.

[Mikey]

Don't know if this is a similar problem. Last week I gave my 300 TDi engine a good clean/degrease with a power washer. Unfortunately the engine developed a squeaking/whisteling belt afterwards. I found that WD40 sprayed onto the belts/pullys stopped the squeak, but only for a short time. This went on for a while, until in desperation I sprayed WD40 into the alternator bearing and windings. It has been silent since then. Not sure why, but it worked.

[Davey1000]

You haven't been getting rid of high resistance connections have you? I've been down that road. After buying a Discovery with charging problems one unscrews the battery earths, power brushes the chassis down to shiny metal and remakes the connection using petroleum jelly. Afterwards the joint is painted over with red oxide to protect it from corrosion. This is a tremendous help but next one notices that the alternator output cable is getting hot. It turns out that the strands of copper wire in the cable lug have oxidised and turned black. It is difficult to clean the wire but a good method is to use a wire brush in a power drill. One gets the brush brushing against a metal block and feeds in the wire between the two. Some wise-guys use ammonia but this is a bad idea as corrosion will recur repeatedly unless ALL traces of the ammonia are got rid of down to forensic levels (lots of boiling water?) Once the strands are clean they can be lightly tinned. They are then crimped into a new lug and soldered. Ideally the lug-to-wire joint should be sleeved with heat shrink tubing but tape will do OK. The problem then arises that because the alternator can now belt out 100 amps, the belt slips, - duh! Spurious pattern part belts will shred within minutes and even the Gates Micro-V on a brand new pulley is only just good enough. Well I've had a gutful and plan B is to ditch the 48.5mm pulley and revert to the 61mm pulley that the original Discovery had. This does need a longer belt, the 7PK1595 instead of the 7PK1580. With any luck it will no longer sound as if one has a flock of birds under the bonnet. Good luck!