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MG MGF Technical - Alternator Belt Tension


I have found my alternator drive belt is badly worn and needs replacing. Unfortunately I don't have my Rave CD to hand (on holiday at my parents). I think there was something in there about measuring the belt tension after fitting the new belt.

If someone has the Rave CD to hand please could they remind me of the contents of this page, specifically how to re-tension the belt.

Thank you.

Peter Stubberfield

The manual talks about mm of deflection under load in pounds. Basicly just like any other drivebelt it should be tight enought that it can be turned over 90 degrees in the centre of the length with moderate effort.

You can see why Rover are more precise!
Will Munns

as Will suggests

Apply a force of 10 kg to alternator drive belt at
mid run of the belt and measure the deflection between crankshaft pulley and alternator pulley. Deflection must be 6 - 8 mm.

Hi what is the correct path for the alternator belt ?
My wifes car has aircon
I can't seem to find the correct path . I was told There was change over in belt length that year- 1998.

The belt goes outside of the crankshaft pulley, the A/C Compressor and Alternator then inside (below) the belt tensioner pulley.
The BT pulley must be released by the end nut and adjusted by the adjusting bolt below the pulley.
If you are still lost, call 422525 and I have a copy of the WSM in L.Spa.
Geoff F.
G. Farthing


Direction is clockwise:
Start from top of crankshaft pully, then under tensioner pully, then up and over alternator pully, then down and under aircon compressor pully and then to underside of crankshaft pully then to the top where you started.

This next bit may be information overload, but here goes anyway,


To Check:
1. Disconnect battery earth lead.
2. Raise rear of vehicle. WARNING: Support on safety stands.
3. Remove road wheel(s).
4. Remove 2 scrivets and Torx screw securing closing panel.
5. Remove closing panel.
6. Check condition of drive belt. Renew a drive belt that shows signs of wear and splitting.
7. Apply a force of 10 kg to the drive belt between crankshaft pully and aircompressor pully, at position directly under and inline with the idler pully. Measure the deflection between the crankshaft pulley and air conditioning compressor pulley. Deflection must be 9 - 10 mm.

1. Loosen nut securing drive belt, tensioner pulley.
2. Increase drive belt tension by turning the tension adjusting bolt clockwise.
3. Tighten drive belt tensioner pulley securing nut to 25 Nm.
4. Recheck drive belt tension.
5. Fit closing panel and secure with fixings.
6. Fit road wheel(s) and tighten nuts to correct torque. (70nm)
7. Remove stand(s) and lower vehicle.
8. Connect battery earth lead.

Hope this helps.



Will print and try it now.
The Female easyout worked on all four locking nuts BTW and will replace with a different (non MGRover)set tomorrow.
I almost could apologise for winning the rugby world cup now , almost !!
Alan. releived in

many thanks for your offer , I re- read your email above and that little detail about the nut inside the pulley (I had undone it previously but nothing happened)is the bit that clinched it.
I think I will tell my wife to buy a WSM on Ebay, she can borrow my tools. I want to get get back top the midget and make a start on the frogeye sprite !!!!.
Will keep your phone # for future reference if that's OK. Alan 774295

Only 3 nuts on each wheel now. On Ebay I see some-one called Dave in leamington is selling locking wheel nuts at about 12 a set.

Sure your wife pays for your efforts.
What is the Reg. of your Frogeye ??
We sold ours locally some 30 years ago. If you have any spare time, then my wife's 69 Stiletto is under restoration in the garage with a 1986 Tax Disc.

Now I am worried. The local tool store sells the Female EasyOut that will remove the MGR Lock Nut without the key drive.
My Astra has a key drive bolt with a spinning outer ring. Does anybody know of this type for the 'F'
Geoff F.
G. Farthing

Thank you. These are the numbers I was after. I used a spring balance and piece of string to apply the load to the belt.

Unfortunately, having reassembled I forgot to remove the piece of string before reassembling so it got wrapped around the alternator pulley. Had to take the wheel etc off again to unwind it. I was very lucky not to get it snagged in the cambelt.....Idiot!!

P J Stubberfield

@ Branko,

is this OK 4you ? ;-)

PS. the manual is wrong in some minor details. Corrected above.
Dieter K.


No Problems, and well done again.

Who needs mechanics when we have your site for info. :-)



This thread was discussed between 31/03/2005 and 05/04/2005

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