3.9 V8 fanbelt adjustment pulley mechanism

**Utemad** · 15th March 2008, 04:16 PM

Hi all.

I have been in need of a new fanbelt adjustment pulley mechanism for a while. I managed to stop the squeal for a while by adjusting the back edge of the unit off the block for a while but it now squeals again.

While my Dad was here (mechanical engineer) he had a quick look.
His opinion of the failure is that due to the offset of the pulley (the load) the bush between the bolt and the rest of the unit gets unevenly worn. This is exacerbated by the fact that the bolts shank does not go all the way through the bush. The thread begins about 13mm before the end of the bush so there is no real support there. You can see the difference in wear when you peer into the bush. Also if you put the bolt into the bush from the side that is normally up against the block there is very little slack compared to when the bolt is put into the bush as it would normally be assembled.

He said if I could punch out the bush and replace it then it would probably be fine (given the spring and whatever else is inside is okay). Also that if I got another bolt (of correct type) that had the shank go within one thread of the end of the bush (to allow for correct torque of the bolt) then it should not happen again nearly so soon (looks original at 195k but been worn out for probably 20k).

Is this news or already a known fault (the bolt being the problem not the bush wearing out)?

What is the correct tension for the bolt?
RAVE doesn't say specifically but it is about 10mm and RAVE says 45Nm for M10 engine bolts.

Has anyone successfully punched out the bush and replaced it?

Thanks.

**101RRS** · 15th March 2008, 04:26 PM

I would have thought it lasting for 195K is pretty good

. Why not just replace and you will get another 195K before you have to worry about it.

Garry

**Utemad** · 15th March 2008, 04:44 PM

Because I like to fiddle

It appears that the front side of the bush has a narrower outside diameter than the rear side of the bush. Probably changes diameter at the change over point of the two halves of the assembly?

I'm going to try and shim the bolt and see what happens.

If all else fails I'll just order a new unit as you say.

**Pierre** · 15th March 2008, 04:51 PM

I've had a problem like yours, but on 300TDI. I've found that the rubber suspension in the bush centre has (or is in the process) broken down - allowing the outer carrier to misalign and "droop", shifting the belt centre off line.

The simple solution is to get a new tensioner. British 4WD in Hobart offer the part (ERR4708) for about $146 + post, but some searching and haggling might yield a better price.

HTH

Pete

**Utemad** · 15th March 2008, 05:16 PM

Not sure where the rubber bit is you mention. The bush on this one is metal.

The part number for this is ERR3440
A Dayco part.

**101RRS** · 15th March 2008, 07:16 PM

Originally Posted by Utemad

Because I like to fiddle

Now that will get you into trouble

- or make you go blind

**100I** · 15th March 2008, 07:33 PM

I haven't pulled one apart to know what you'd need but try Allied Bearings at Ashover rd Rocklea, they have a surprising aray of bushes.
BTW I'm with you, I'd rather repair something if I can just to see if I can, and also improve it so I or the next person needn't bother with it again.

**Utemad** · 15th March 2008, 08:04 PM

I'm not game to punch the bush out til I have another unit as it is my daily driver. I will however be pulling it apart when I do. Til then I'll shim the bolt and see what happens.

**sclarke** · 15th March 2008, 08:26 PM

I would just replace it...
They are not that dear considering how long they last....

Try the front timing cover on the 300tdi.... Bearing fails at 200k and the front cover assembly is $500..........

**Pierre** · 16th March 2008, 05:31 AM

Typical - some bits common, easy ones different. Can't remember what a V8 one even looks like! But surely it's not going to be that expensive, not like a 300 tdi timing cover, as Clarkie says.

Pete

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