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MG MGF Technical - Driving surge / resistance - squealing aux belt

Hi Chaps & Chappesses!
this is a real conundrum at the moment and something that doesn't seem to fit (but then my knowledge of modern cars is limited - by choice!!)
have an MGF VVC '97 (going rusty!!) the auxhiliary belt is squealing under acceleration and sometimes also when cruising. When it does you can feel resistace building up in the car - similar to when you drive thru standing water - and then when the squealing subsides the car surges and returns to normal driving until the belt squeals again.
Noticed it on friday on the M62 heading both directions and since the aux belt has been chittering.
Is there a direct connection I'm not aware of between the incidences of belt squeal and resisitance surge or is it just coincidence? I thought the aux belt just drove the waterpump and alternator. there doesn't appear to be any incresase in engine temp / reduction in electrical activity elsewhere when the squeal / resistance occurs?
Is the belt reducing the consumption buy the coil pack causing it to fire intermittently? It's a guess, but would like a 2nd , 3rd & 4th opinion! Coil pack is recentish - c 10k miles & car lives outside all weathers.
Belt is due to be changed out tomorrow - (not by me) Just need to know if there's anything else Ishould be looking for.
cheers
andy
Andrew Tyson

Hi Andy,

The water pump is driven by the cambelt. The aux. belt drives only the alternator and aircon - if fitted. Getting the belt changed tomorrow should be treated as urgent as it's been slipping for some time. If that belt breaks it can get itself entangled with the cambelt with disastrous results. If the new belt shrieks as you first start the engine it will need further tensioning.

HTH

willyphixitt
W A Nixson

Hi, Thanks. Already booked in but is the "surge / resistance due to the belt sipping or should I be looking at other components?
cheers
andy
Andrew Tyson

When you have the belt changed, also have the alternator and battery checked.
The only connection that might cause both faults is that the slipping belt has caused the battery to lose charge.
Geoff F.
Geoff Farthing

Maybe it is the other way round and the noise is caused by something like alternator or waterpump bearings on the way out, randomly finding a stiff orientation and causing the belt to slip. Either way replacement tomorrow sounds good!
Charless

I think Charless makes a good point, as would be the case with air con. When the aircon compressor loads up so does the load on the engine and belt and could cause the type of effect you describe as can the other things noted above. Does your car have aircon?
Robert (Bob) Midget Turbo

This could be a heavy electrical load, such as an intermittent short circuit. As it starts to draw high current it makes the alternator hard to spin to the extent you feel the drag in the cars speed, and the drive belt cant transmit the torque. If it it still does it after a belt change then maybe swap out the alternator, it could be an internal fault. Failing that it will looking for a short, it must be before any fuses as it would open them, if it is a short.
Stan Best

I have similar problem but not to the extent you mention. Its a rare occurance and only happens when there's been a heavy down pour of rain that I hear the squealing.
P A Blundall

If the squeal only happens when there's water around, that means water is getting onto the belt, which will then slip and let the alternator decelerate, so the ignition circuits will pull charge from the battery which will result in a small voltage drop, which will be felt as a loss of power as the spark weakens.

The closing panel in the driver side wheelarch is there to protect the belt from spray, so the first check is that it's in place and firmly attached. It also protects the exposed part of the cam belt, so its importance should not be underestimated.
bandit

This thread was discussed between 04/10/2010 and 05/10/2010

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