Monday, 10 May 2010

WTF!! Where's my Idler / Deflection pulley??

Recently I'd been trying to find the cause of a squeal or whistle from the engine area under gentle acceleration between about 1200-2000 rpm. I had my water pump, thermostat and belts changed about 18 mths ago and noticed the squeal start BEFORE that job was done.

I found some great vids over at bimmer forums, a user called BimmersGarage, which are posted on youtube. Whilst watching the vids i noticed that the arrangement of his pulleys and his drawing were not like mine from what I could remember, so i went out and checked, and sure enough it looks as though my idler pulley is missing!! Was my tensioner pulley taking up the slack???

Below is the schematic diagram by Bimmersgarage showing the lay out of the belt, tensioner and pulleys.

In the 1st video, 10 secs in it very clearly identifies the pulleys, and its pretty clear when you look at the pic of my car that there is NO DEFLECTION PULEY (part no 15 here) I've not noticed any significant ill effects from not having this, but what could be the possible ill effects of this??

Well I posted this problem up on E46Fanatics, and after people doing some head scratching and digging, the long & short of it is that not all M54/52 engines had the defelction pulley, if this was the case it appears to have been on Euro cars. Below is a pic I took of the TIS manual which clearly shows that not all had the "Auxillary Tensioner Roller" as BMW calls it.

So in the end i could rest easy that my M54 wasnt missing some vital parts. In fact it might even release a few more bhp...... new mod.........deflection pulley delete!!

1 comment:

  1. Hi, I don't have an idler pulley on my E46 either. How did you route the belt back onto the pulleys? Did you route the belt back on to the tensioner last? Thanks Vin