Belt jumping

[dave225]

A few times now my accesories belt has jumped sideways a couple of grooves on the A/C compressor pulley. Each time I recall I've used some higher revs. Easy to get back of course, but I reckon the belt tension is slacker than I think it should be - is this the signs of a knackered tensioner?

Apart from getting a replacement - is there a manual tensioner that can be used in place of it? or were they just on the older engines? (My F-reg 2.0 non-turbo non-A/C had one).

[Mark B]

Remember that the tensioner is actually a damper as well. It's generally the damping getting weaker that allows the belt to jump. I'm not sure that a simple manual tensioner would be a good idea on a car with air con as it is the compressor engaging that causes the biggest transient loads which the tensioner/damper combination is designed to allow for.

[chris aka zaphod]

Might be worth checking all the pulleys, for bearing wear, and check the belt hasn't stretched before condemning the tensioner.

[phoenix]

Jumping a tooth or two is normally a sign that the tensioner is failing, but it is definitely worth checking the pulleys etc. The other thing that may be causing the problem is the A/C compressor if say the expansion valve was partially blocked that would cause a very high load.

I'd agree that you wouldn't want to use manual system. IIRC older models that had manual tensioners tended to have multiple belts that were shorter. It is in part the length of the belt that necessitates a dynamic tensioning system.

[dave225]

Just got a new tensioner unit, but I can't budge it leanng all my 12 stones on it! Does anyone know if it should move "by hand"? The old one moves quite easily when leaning on it, but then I'm not sure how knackered it is.

[chrisw]

There is a special tool for doing the belt tension  detals were on the old forum which i cant access now (seems it doesnt like my email address so no password reset).
basically its either a spanner with a very large lever (mines 30inches long) attached to it, or you can make a belt compressor with a bit of DIY engineering and a suspension spring compressor.
I had to change mine a couple of yrs ago due to the same reason its def sounds like yours is knackered if it wont compress.

[chrisw]

 hi got this link from the olde saabscene website
a 3rd alternative to my suggestions
I hope it helps.
http://saab9000.com/procedures/tools/tensioner.php

[Mike9000Aero]

If you don't have the special tool lean on it for a bit as you have to overcome the dampening effect and it will slowly retract. Don't forget one of the bolts is opposite thread.
Mike

[chris aka zaphod]

I did a bit of a bodge and lowered the tensioner on an extended axle stand, and let the weight of the car do the work. As a former H&S senior consultant, not recommended, unless you have done a risk assessment, first  !

[dave225]

Epilogue:-
As I eventually realised - and others already knew - the LH thread is so you can use a breaker bar to lever the tensioner down to get the belt on. It seems a new unit can't be sucessfully compressed by hand (without ruining the hand).
I'll know for next time!