screaming alternator belt

[martymart]

1.9 dg engine

The alternator / timing belt screeches like mad on start up and first few revs of the engine. Once its warmed up the racket goes away. Is this anything to worry about and/or can I do anything to eliminate it?

Any suggestions would be greatly appreciated

cheers

Martin

[marlinowner]

It means its too loose and slips when the alternator is working hard. There should be about half an inch of up/down movement in the centre of the belt on the part of the belt with the longest run between pulleys. To adjust, slacken off the alternator bolt that attaches the alternator to the slotted bracket and lever alternator away from engine until belt tension is correct. Don't overdo it, if the belt is too tight the alternator bearings will suffer. If it still screeches, then maybe a new belt is in order.

[CovKid]

Hmmm, don't assume its the alternator belt. I say this from hard experience. Belt AND pump make very similar noises and tightening the belt will often silence either or both - for a time, but leaving the problem unresolved is asking for trouble. The important thing is establish which.

Remove the belt completely and grab hold of the waterpump pulley (you can't really check with belt on). If it has play in it, the bearings could be on the way out and that screech is the first indication that the pump is knackered. It can come and go - often first thing. Many assume its the belt, tighten it (which takes up play at pump pulley) and then forget about it. If the pump is wearing, eventually the bearings will collapse (when they feel like it) and/or pump will begin to lose water catastrophically. If it happens on the road, and chances are thats what it will do, it isn't fun. The engine will overheat rapidly (within minutes) and it can be costly. If pump fails, you MUST stop immediately and get a tow home.

Test: https://www.youtube.com/watch?v=LghNy400HzI" onclick="window.open(this.href);return false;

If pump is worn out, follow: https://club8090.co.uk/wiki/Co ... overhaul_3" onclick="window.open(this.href);return false;

If its just the belt (less likely in my experience), you can roughen the pulleys to increase grip and fit a new toothed-style belt but I'll bet its the pump....

[ghost123uk]

I'll bet its the pump....

How much do you bet? I'll bet 2 pints it's a slack belt. (But while you have the nuts loose to adjust it, best check the bearings anyway )

[CJH]

One more thing to check:

I had a squealing belt, even though I'd recently tightened it. It turned out the bracket at the base of the alternator was broken, so the whole alternator was loose. Easy check - with the belt on and both alternator bolts done up tight, try rocking the alternator forwards and backwards - there should be little to no movement.

[Timburrows]

Could also be pulleys worn so the belt is tight in the bottom of the pulley when tightened but soon lose as it's not being gripped by the sides of the pulley as belt is to narrow or the pulley is to wide

[martymart]

All

Thanks for the suggestions. I've checked the tension on the belt previously and it felt Ok to me. The inner face of the pulleys is polished and shiny so I could see some slippage occurring there. I'll slacken it off as suggested and see if there is any play in the pump or alternator but not the news I was after when I have a 100 mile run to bus fest this weekend!

I'll update later when I've had a look

Cheers

[Ralf85]

If it's the pump it should give up about half way to Busfest!

[itchyfeet]

You missed coolant on the belt, dripping from somewhere, soon dries off.

[martymart]

Bugger!

Well did the checks, removed belt roughed up the contact surfaces with emery, refitted and retentioned and it still squeals like a stuck pig!

There is some very slight play in the water pump pulley,about half a milimeter or so, so I'm going to have to replace it. The worry is, the run to Busfest this weekend. I'll be watching the temp guage all the way!!!

[CovKid]

What was that about TWO pints of beer John? Will hold you to that.

Well, its not really a solution but you could try a squirt of oil behind waterpump pulley and see if the little that works into bearing quietens it until you can get the pump swapped. You do at least have the luxury of a WIKI 'how to' including all the potential probs you may encounter. Definately replace it before Winter. They start noisy, then fail not too long after so best done. I'm sure you'll get to Busfest and back fine (no bets this time though).

At least you got the warning.

Check alternator too although you tend to get a rumble rather than a squeal with alt bearings.

[Timburrows]

Bugger!

Well did the checks, removed belt roughed up the contact surfaces with emery, refitted and retentioned and it still squeals like a stuck pig!

There is some very slight play in the water pump pulley,about half a milimeter or so, so I'm going to have to replace it. The worry is, the run to Busfest this weekend. I'll be watching the temp guage all the way!!!

Could try crimping the pulley with a pair of mole grips(other grips are available) to tighten it up temporary set right they would squeeze the pulley evenly if it's made of tin

[CovKid]

Except, thats not the cause of the squeal - in this instance its the pump. As they reach the end of their working life, they make this noise on startup and even worse in cold weather. Once the water starts circulating, the bearing often shuts up but its merely a prelude to more extensive wear and failure. As I said earlier, commonly people overtighten the belt to compensate as they assume its a slipping belt. This then puts load on the waterpump bearings, which temporarily makes the noise go away (play removed). They are even more convinced its the belt then and it becomes a vicious circle, over-tightening the belt, accelerating pump bearing wear, creating more slippage, more polishing to pulleys until pump has had enough and finally gives out. The only solution is a new pump - sooner, or indeed, later.

Crimping pulleys? Nice idea but you can't do that without distorting them and its still doesn't address the cause. You'd be masking it. In the case of a slipping belt, its better to use that sticky anti-squeal stuff they sell specifically for the job.

May find this useful: http://www.youtube.com/watch?v=MR3t71Lhoy0" onclick="window.open(this.href);return false;

And: http://www.classic-car-buyer.co.uk/feat ... ump-wisdom" onclick="window.open(this.href);return false;

If only the 1.9DG waterpump came off that easy