Drive belt popped off!?
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Veteran Member
Joined: May 2014
Posts: 5,906
Likes: 2,182
From: Bremen, Germany
Drive belt popped off!?
Hi there,
I normally lurk in the X308 and X27 sections of this forum, but have a patient with something I have yet to see again.
It is a 2001 XKR coupe. Metal tensioners, good overall condition. About 125k mikes on the clock (200k km). Engine runs smooth, everything works. Except...
As I was with the owner to buy it, the tensioner arm for the serpentine belt would 'snap' every so often when it was really cold. Like -5°C (really cold for my area of the world). One morning, my friend wanted to take the XKR for a spin, but it started and the serpentine belt just come off, straight after starting and remained there then for 3 months until I had time to set it up again.
Was a pita to get it on again yesterday (we all know how cramped that engine bay is). As it was refitted, I started the car: no snapping of the tensioner arm (snap = gets stuck, tugs round, loosens off a again and males a bang sound like knocking metal on metal). The car ran like a gem.
Today was around 10°C, yesterday about 15°C. Both times no nasty noises.
What would you say could be the culprit? The alternator, waterpump, powersteering pump and air con compressor all turn easily for what they are (the compressor harder if you turn the non-clutch part - normal though). The pulleys are fine (one seems to squeak).
My thoughts are that the belt is too new/too stickey and tends to get stuck to a pulley or so resulting in the belt getting stretched back and forth... Or that the tensioner arm is damaged but it is attached to temperature...
Any thoughts, guys?
Cheers
Damien
I normally lurk in the X308 and X27 sections of this forum, but have a patient with something I have yet to see again.
It is a 2001 XKR coupe. Metal tensioners, good overall condition. About 125k mikes on the clock (200k km). Engine runs smooth, everything works. Except...
As I was with the owner to buy it, the tensioner arm for the serpentine belt would 'snap' every so often when it was really cold. Like -5°C (really cold for my area of the world). One morning, my friend wanted to take the XKR for a spin, but it started and the serpentine belt just come off, straight after starting and remained there then for 3 months until I had time to set it up again.
Was a pita to get it on again yesterday (we all know how cramped that engine bay is). As it was refitted, I started the car: no snapping of the tensioner arm (snap = gets stuck, tugs round, loosens off a again and males a bang sound like knocking metal on metal). The car ran like a gem.
Today was around 10°C, yesterday about 15°C. Both times no nasty noises.
What would you say could be the culprit? The alternator, waterpump, powersteering pump and air con compressor all turn easily for what they are (the compressor harder if you turn the non-clutch part - normal though). The pulleys are fine (one seems to squeak).
My thoughts are that the belt is too new/too stickey and tends to get stuck to a pulley or so resulting in the belt getting stretched back and forth... Or that the tensioner arm is damaged but it is attached to temperature...
Any thoughts, guys?
Cheers
Damien
Last edited by Daim; Apr 23, 2017 at 09:13 AM.
Senior Member
Joined: Jul 2014
Posts: 812
Likes: 268
From: Damnville, Virginia
My '97 XK8 did that banging noise when cold and eventually threw the belt. It was the bearing in the belt tensioner pulley doing it. When cold the bearing would bind causing the belt tensioner arm to snap back making the sound. I replaced it with a metal pulley with new bearing and also replaced the stationary idler with a metal one with new bearing. No more problems after that.
Here is the thread on it starting at post #22.
Dave
Here is the thread on it starting at post #22.
Dave
Last edited by DaveInVA; Apr 23, 2017 at 08:19 AM.
