Squeal when decelerating when hot

[Bucksspeedyboy]

Hi all, I have a 2001 1.9 Z3 which has done 80,000 miles and is used daily. A couple of months ago, when the weather first got warm, after a period spent in stop-start traffic it suddenly developed a squeal that appeared to be coming from the engine somewhere (!). But it only happened when decelerating/ taking foot of the accelerator, it didn't happen when accelerating and apart from the noise the car ran fine. When I finally parked, the squeal continued until the revs dropped right off. That evening going home, all was fine until after about 20 miles or so the squeal started again. At the time I wondered if it was a belt slipping or something when the engine got really hot in the stop-start traffic. It went into my usual garage a couple of days later for them to check it out, but they couldn't find anything or get it to make the noise again. Since then I've had it intermittently, always when the car has been running a while and got really warm.

Last night, I was stuck in long stop-start traffic on the M3 and then the M25. It was a very warm evening and sure enough, after a while the squeal started and got progressively louder the longer I was in the traffic. Eventually I got off the M25 and sat for a while to let the car cool down (the engine wasn't overheating or anything though). When I set off, the squeal was still there whenever I took my foot of the accelerator, but it got progressively quieter as I drove home for about 30 miles at a reasonable pace in non-motorway traffic and the air temperature got cooler (it was about 8.30 pm). By the time I got home, the squeal had just about disappeared. This morning I did my usual journey to work - about 20 miles with a mix of traffic conditions; there was no squeal at all. Any ideas?

[Del]

Personally I would suspect either a bearing e.g. water pump, tensioner pulley, alternator or a possible problem with the viscous fan coupling - which is supposed to lock and spin faster when the engine gets hot. From by own 1.9 experience, the bearings I've mentioned will all be getting tired at 80,000 - particularly water pump and tensioner

[Bucksspeedyboy]

Hi Del, thanks for this. I don't think it will be the water pump and tensioner as I had the pump go about 10,000 miles ago and so had a new one fitted. Thanks for the other suggestions though.