Alternator bearing problems?

Johnny C · Feb 12, 2008

I had a high-pitched whine coming from the rear end (of the car not me) which I thought might be the clutch starting to die (it's got at least 50k on it). Well, it turned out not to be from the clutch. Main clue was a bang, a burst of smoke and the smell of burning rubber. A non-Porsche alternator belt had been slipping when I let the clutch out and basically melting, there are bits of melted rubber scattered around the engine compartment.

So a porsche one was fitted (at no cost). The bearing on the alternator seemed fine, but the squeak has returned when I'm dropping revs coming up to a junction and I accelerate quickly it if the traffic lights turn green. At least the belt is intact, it's due in for a service so will get the alternator checked out properly.

Has anyone else had a problem like this? Bearing runs fine when you turn it by hand, but for some reason when you're dropping revs then accelerate quickly it sticks?

burrow01 · Feb 12, 2008

Hi,

Is it the bearing or is the new belt slipping?

Pete

Johnny C · Feb 12, 2008

The noise is coming from the belt, but only under those circumstances. I'm assuming that the bearing is okay in 'normal' operation but when the rotation of the drive pulley increases significantly the bearing can't cope. Any enlightenment appreciated!

Porker993 · Feb 12, 2008

I had it on my 964. A bit of WD40 works wonders - cures the squeal for a few weeks. The only long term solution though, is three new OE belts fitted by someone who knows what they are doing using all the right shims etc. Not a DIY job in my experience, unless you know what you are doing ...

Johnny C · Feb 12, 2008

partly why I think it's the bearing and not the belts, new Porsche belts were fitted by 9M last week. Took a few goes to get the right alternator belt, they come in two sizes and it depends on what the mechanic who initially fitted it had for breakfast as to which size it is.

The old one melted on the way home so I got recovery to take the car to 9M, it's 20 miles and I wasn't going to risk it dying on the motorway. The garage who came to recover it offered to fit a new one, he said he thought he had the right size in stock and once fitted one on a Porsche. Like I'm going to choose that option over getting the right belt fitted properly!

Porker993 · Feb 13, 2008

I've never head of the alternator bearing going on a 993, though it's not impossible I suppose. Time for a second opinion, methinks.

burrow01 · Feb 13, 2008

ORIGINAL: Johnny C

So a porsche one was fitted (at no cost). The bearing on the alternator seemed fine, but the squeak has returned when I'm dropping revs coming up to a junction and I accelerate quickly it if the traffic lights turn green. At least the belt is intact, it's due in for a service so will get the alternator checked out properly.

Has anyone else had a problem like this? Bearing runs fine when you turn it by hand, but for some reason when you're dropping revs then accelerate quickly it sticks?

Hi,

This was exactly the same symptoms I had with a slipping belt - maybe it just needs retentioning?

Pete

tomwinton · Feb 13, 2008

When I got a belt that slipped in the wet - they diagnosed it by squirting WD40 on the belt itself.... guess this could be a good way of checking belt vs bearings....

Johnny C · Feb 14, 2008

Well, it's a moot point now. it made some horrible squealing noises on the way home last night, I thought the clutch had gone. Seemed fine this morning, tootled in to work. Halfway (just past the turn off to 9M) the airbag and ABS light came on, which is a sign the electrical power isn't enough (for some reason the battery light hadn't come on). Then 2 miles on the headlights started to go dim so turned them off. Then another mile on the stereo went off (had only kept it on for traffic alerts). I thought 's**t' and pulled over to the slow lane for when the engine finally died. It kept on going though, the warning lights getting dimmer and dimmer until I finally limped into work. Belt's fine so the alternator has gone completely. As luck would have it it's booked in for a service tomorrow, so I'll get the recovery man to recover me there again.

I certainly get my money's worth out of AutoNational!

Porker993 · Feb 15, 2008

That's an interesting experiment which seems to show the 993 engine can keep running with a flat battery ! You did not even have enough current to power the radio, but there was enough to deliver a healthy spark to twelve spark plugs. How odd. Maybe one of our resident autoelectrical experts can explain ?

Johnny C · Feb 15, 2008

I know zilch about the electrics, I wondered if the electrical had some waterfall limiter system so that current was preserved for the door locks/immobiliser and engine and maybe lights, then surplus for electric windows and sunroof (which take far more power than a standard stereo radio) and other bits like that, then surplus for the stereo, ABS and airbag is last.

Alternator is definitely gone. I got recovered to 9M but the archways going in only have 10ft clearance and the truck was 10ft 6", so they brought a battery out to jumpstart it and get it round to the garage. I drove it 400yards, the engine was still cold to the touch but the alternator pulley was too hot to touch.

The alternator went on my old 3.2 on the M6 once; the battery light came on at J8 (M5 link) and I got up to J16 before it died completely, but that was with the leadlights on and a smaller battery.

I reckon that I got just short of 50 miles out of it, but that was driving without any lights on and (for once!) the rush hour traffic on the M62 between Warrington and Manchester wasn't too bad, fairly steady. If it had been stop-start I doubt I'd have got as far as I did.

It is good to know that if a belt goes on these cars you're not stuck in the middle of nowhere, I've done 30miles on the motorway with no fan belt at a steady 50-60, you couldn't do that in a watercooled car

Porker993 · Feb 15, 2008

ORIGINAL: Johnny C
It is good to know that if a belt goes on these cars you're not stuck in the middle of nowhere, I've done 30miles on the motorway with no fan belt at a steady 50-60, you couldn't do that in a watercooled car

That's what I was thinking - no way could you do that with a water cooled car. On a 993, even if the alternator belt goes, you still have engine cooling.

Hope you get it fixed soon and it's not too much dosh. [

]

Johnny C · Feb 15, 2008

Hope you get it fixed soon and it's not too much dosh. []

LOL, when was it ever not too much dosh?

The alternator can be replaced if you're lucky without engine out, but as the clutch is almost certainly on it's last legs (50K+ on it) they're going to drop the engine and check the clutch and replace that if it's within 0K of it's life, which saves a bit on the labour of dropping the engine for both jobs separately. Was toying with the option of a low-mass flywheel, but as most of my driving is motorway commuting with only the odd blast through the Welsh hills, it's not worth the aggro. I know a remap would help with the cold start stalling problems and gearbox chatter but it won't cure it without a MOTEC job and the cost of that isn't justified given that I'm a motorway-eating porschemonkey rather than a trackday one.

One thing for anyone who's ever recovered to 9M - the archways on the way in have a 10ft clearance. Never been a problem before (and I've been recovered there often enough in the past) but some of the newer recovery trucks have a 10ft 6inch top, so make sure when you phone the rescue people that you tell them there's a 10ft clearance on the way in. It's okay if the car is rollable with steering - it can be pushed/jump started through, but if steering had gone say then you'd be stuck.