P38A DSE fan belt tensioner bouncing and rattle

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johnnie4x4

New Member
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5
Location
Newtown Mid Wales
The aux belt tensioner is bouncing around and on a couple of occasions has gone over center and then alternator light comes on. I can get out a flip back but I am wondering if my crank damper is worn out. It does not seem to be lose and does not appear to wobble, see video.
As I have nothing to compare to are they all this rattly, have got a Disco 300 which is quieter. Any advice appreciated. It is a 1997 auto, not that that will make any difference.
 
How easy is it to move the damper assembly. On my own I need a foot long screwdriver to shift it and when it starts to move it goes very slowly due to the resistance.
 
johnnie4x4 said:
The aux belt tensioner is bouncing around and on a couple of occasions has gone over center and then alternator light comes on. I can get out a flip back but I am wondering if my crank damper is worn out. It does not seem to be lose and does not appear to wobble, see video.
As I have nothing to compare to are they all this rattly, have got a Disco 300 which is quieter. Any advice appreciated. It is a 1997 auto, not that that will make any difference.
Click to expand...


Should be smooth with little bounce. The tensioner arm tends to crack. Some people reinforce them. I'd advise not going Britpart unless you want to replace it every 3 years.
 
Mark Piercy said:
How easy is it to move the damper assembly. On my own I need a foot long screwdriver to shift it and when it starts to move it goes very slowly due to the resistance.
Click to expand...
I used a long bar about 2ft long with a bend on the end of it, is for removing wheel nuts and just the right shape, problem is top hose gets in the way with a straight one. Does your engine sound as rattly as mine?
 
The tensioner pressure spring unit is oil damped. Damping oil can be lost over time. Remove it and check for damping oil.
 
As above its very likely the little tensioner, mine was exactly the same on my 5 series. No damping effect and very worn bushes, I think it was around 20 quid off the bay
 
I am no authority on this but just from my experience the tensioner you're showing, mine went through 2 of them, then my mechanic took the one in my pic apart cleaned it out and put it back again, and I never had any trouble after that

20190131_154142_IMG_0214 (1).JPG
 
1682928964202.png
the bolt/disk to the right of the picture.
Be very careful when tightening the little bolts back into the aluminum as they can strip the threads really easily. A little thread lock to help.
When undoing the Allen bolt disk the whole assembly may turn if it's been over tightened as well.
 
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