Twittering Multi-Rib Belt - XM 2.5

rg · Post by rg » 11 Jun 2005, 01:51

Folks,
I changed the aux. belt on my XM recently, and adjusted it to the advised tension, namely 5mm deflection under "firm thumb pressure" on the longest run.
It now "twitters" for around two minutes on start up.
I hate over-tightening things, and fear for the life of my alternator bearings, but I seem to recall that these belts need to run at a considerable tension, that is, erring on the side of tight rather than loose. Firmer thumb pressure makes the belt deflect around 12mm (ish!). Is twittering always a sign of a slack belt?
Any advice and insights welcomed!
rg

jeremy · Post by **jeremy** » 11 Jun 2005, 01:56

Probably the problem - used to get it on my BX if I wasn't careful as someone had lost the tensioner bolt.
I made a new tensioner which solved that problem. I now have a noisy belt which responds to silicon spray - must chuck it soon!
I don't think alternator bearings are that feeble are they?
jeremy

rg · Post by rg » 11 Jun 2005, 02:14

I've just replaced the alternator on my Isuzu 4x4, but not through belt abuse, so I'm a bit sensitive.
Silicon spray worked well on the 4x4 when the belts were getting elderly and worn.
rg

citronut · Post by **citronut** » 11 Jun 2005, 03:39

multi rib belts do need to be tighter than V belts ever used to be,if it twiters it needs tightening regards malcolm

BX-Basis · Post by **BX-Basis** » 11 Jun 2005, 03:59

If the XM has AirCo (it most likely will have AirCo...), the belt must be tightened very carefully. There are 2 tensioners. One automatic tensioner and one manual tensioner. First of all you insert a 4 mm bolt in a hole at the tensioner to block it. Then you tighten the belt with the manual tensioner. The tension is ok when you can take out the bolt withou forcing it. After that you turn the engine 10 times (the belt makes exactly 1 turn). To check if the tension is correct, you must be able to insert a 2 mm bolt into the tensioner's hole. If not, just repeat the procedure...

rg · Post by rg » 11 Jun 2005, 08:19

BX-Basis,
Thanks very much. It's non-air con., and I've got the instructions on how to adjust.
Thanks
rg

BX-Basis · Post by **BX-Basis** » 11 Jun 2005, 14:50

A non-AirCo XM 2.5 ? What a rare thing ! (at least in Germany) Good luck and don't forget to have a look at the hidden water pump belt on the other side of the engine. Many 2.5 owners don't even know that there is another belt until it breaks...