The alternator belt has been slipping on and off for a while, then eventually it snapped. Before it snapped the belt had been tightened because of the slipping noise. Since then the alternator and PAS belts have been replaced but the alternator belt is still slipping. It seems like the belt won’t stay tight. This all started after I had the cam belt and water pump changed. All work has been carried out by a mechanic, not me. Is there anything else we should be looking at that would cause slippage or any reason the belt isn’t staying tight. 1998 MK1, manual, no air con.
if your new belt is slipping, it is either not tight enough or there is a partially seized pulley somewhere.
These belts need to be quite tight - check the adjustment specified in your manual. When you press the long run of belt with your thumb, it should only move a small amount. If the belt has become too loose make sure that the adjuster bolt and the adjuster mounting bolt on the alternator are tight. There is a retaining bolt at the base of the alternator that should also be tight but unless this is missing, your belt will not loosen if this bolt is loose.
If the belt is tight enough, check the pulleys on your alternator and waterpump. Maybe one of these is causing the problem. The ribbed alternator belt on my MK2 snapped recently when the alternator partially seized.
Thanks. We’re thinking it might be the alternator sticking, but can’t understand why the belt keeps slackening off. All are bolts are present and have been tightened as much as possible. I’ll re-post this afternoon after it’s been looked at again.
All checked and re-tightened. Hopefully slipage caused by belts finding their place on the pulleys so just needed nipping up again after use. Alternator, PAS and water pump (which is new) all turn fine with no sticking. Fingers crossed its all ok now. I suppose i’ll have to take it for a good blast to test it, shame that!
Update; drove the car from cold a short distance, parked left for 30 mins, started up and got the squealing slipping sound again. Checked the belts and both seem tight. Will leave the car over the weekend and test it again on a short run next week. Anyone got any ideas?
Just tried car again and belt slipped for a few seconds on start up then was fine. Both belts tight. Any thoughts anyone? Is it something I might have to live with?
When I fitted a new belt, I had to tighten it up twice in the next week or so, then it’s been fine ever since - I guess it naturally expands a bit. Sounds like yours is doing something odd beyond this though, if you’ve checked the bolts are tight, not sure what else it could be (though check it’s definitely the right type of belt as someone else mentioned!). I think you’d definitely be justified in going back to the mechanic and asking him to check his work. Could any of the bolts be crossthreaded and maybe not as tight as you think??
had to readjust mine a few times once replaced befor it finally settled down, but that was a “V” belt. Sounds like yours is what I know as a “serpentine” belt which is a flat multi ribbed type. Check your manual but I have always found these need to be much tighter than a “V” belt to prevent slippage.
When adjusting the belts it is VERY IMPORTANT to loosen the bottom alternator bolt ( this can be a bit akward so people tend not to do it ) fit the belt adjust as neccessary then tighten the bottom bolt fully.This bottom bolt can also be tight on the threads but the actual housing where the bolt passes through the alternator can be elongated or oval shaped from previous person not tightening it properly last time,; Hope this makes sense but may well be the problem!!
Thanks Robert. Bottom alternator bolt was defiantly loosened before attempting to change/tighten belts. As to the condition of the bolt housing, I’m not sure. Just tryed car by the way and it didn’t slip this time. Thanks for everyone’s input. I’ll keep this updated with any developments.
Found the slipping belt problem to be the alternator adjusting bolt keeps coming loose. Would changing the bolt and block cure this or is it a sign of another problem?
Thanks Rob