Question: RE - serpentine belt tensioner

Procomm

Procomm

Club Member
Jul 10, 2007
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Gradually Decomposing in a sarcophagus of general
As in the title, does anyone know what sort of mileage to expect from a belt tensioner? I have a strange issue on Gems Cougar where the Serpentine belt Tensioner rocks back and forth as the engine turns over and obviously moves faster the more you depress the loud pedal, now curiously in time with this rocking motion the lights on the car (for want of a better word) flicker, this is all lights so interior light, dash bulbs, stereo light, headlights, side lights tail lights brake lights, reverse lights and even side repeaters or hazards could this be connected or just a coincidence, what do you reckon?
 
Quicksilver said:
Do you notice any difference with the air-con on or off or the steering held tight on one lock or the other?
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no, no change, one thing that I am wondering though is the alternator was done by a garage and they removed the driveshaft to get access to the alternator, I am thinking that there may have been some damage done to the tensioner as they did manage to screw up the ABS with some magical fuse shenanigans thrown in, lights didn't flicker prior to the alternator failing which is why it is annoying me, I hate letting some half trained gibbon loose on one of my cars as I have always had issues to fix afterwards but unfortunately health and time constraint made the decision
 
Have you tried releasing the tension on the belt and spinning the idler to feel/hear if it's 'catching'. If it is it could be momentarily 'stalling' the belt and the alty.
 
yes tried that last night though I was possibly to cautious putting a bar against the tensioner and pushing whilst the engine was idling maybe could have got a bit more pressure on it but was worried about snagging the belt or a pulley wheel, either way I think the tensioner needs changing as I don't think it should be moving back and forth but thought I would ask the question first of how long they are supposed to last as I have never needed to change one before
 
i have found with some tensioners that removing belt and using a spanner/socket move the tensioner through it full range a few times can help, obviously when the belt is off it will move to fully apply position due to spring but rotating it back as far as it will go a several times, but not forcing further than it should travel sometimes allows the spring to "reposition" or clear crap from its range of movement and let it settle, it's worked a few time but not always but its free to try
 
my lights flicker when the revs are low - cheap replacement alternator in my case. i am sure my tensioner flicked like that when the idle wheel went
 
If most accesories are working well, I'd have to go with the tensioner. You're not going to notice brief problems with the aircon or PAS, but you'll damned well notice charging issues (a-la flickering lights).

Have you had the belt off and, if so, what does the running face look like?

Seriously though, if the tensioner is bouncing? It can only be a bent shaft on an accessory (alty?) or a weak spring on the tensioner itself.
 
its a really easy job to change the bearing in the idler wheel and far cheaper then buying a new one - just need a toffee hammer :)
 
Hi Paul...tensioner on mine was completely fubar at 120K, spring and bearing.

What mileage is Gem's car on?
 
Did you get to the bottom of this Paul?
If so was it the tensioner or the alty at fault?
 
This issue has reared its ugly head again, car is running nicely until lights or heater or heated screens are switched on then it starts hunting, save you all scrolling back through the posts, brand new 130amp Bosch Alternator fitted, Brand new 096 battery fitted, Brand new Mega Fuse fitted, battery tested and holding charge at 13.5V with engine running charging at 14.7V headlights and side lights used to flicker, I have changed them for HID's and LED, still flickering but you cant tell. I am diagnosing a power drain somewhere in the electrical system but I am not sure how I can narrow it down, interestingly the serpentine belt tensioner is rocking whilst the engine is running and the lights flash in synch. can someone please let me know if the tensioner is supposed to rock, its about 5mm of movement I suspect the idler pulley needs replacing but should the tensioner move?
 
No. The tensioner should not move at all. If it does, it's either faulty or something is dragging and causing it to bounce.
 
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