Need help changing my belt - problem with hydraulic tensioner

nishsab · Jul 27, 2011

Hi Guys,
I feel like I'm losing my mind. I read a bunch of DIY posts and thought I could replace my belt myself. I was able to change the a/c belt without any problems. However, I can't get the hydraulic tensioner to release tension on the multiple component belt. I've tried so many times the bolt is starting to strip. I'm attaching a picture of the belt system. I highlighted the bolt i have been trying to turn. My understanding is you turn the bolt at the top of the hydraulic tensioner clockwise and it will release tension on the belt. How hard am I supposed to press because I can't seem to press hard enough? Is it possible the tensioner is broken and that's why it won't release? Am I trying to turn the wrong bolt?
Please help!!!
email: nishsab@gmail.com
Any advice/guidance on what I'm doing wrong would be greatly appreciated.

A less important question, anybody know where I can get another bolt in case I completely strip it? Would a hardware store stock it?

I can't thank you enough!!!

540indiana · Jul 27, 2011

I had trouble with this as well. If I remember correctly, you will need to loosen the bolts immediately to the right of the bolt you are trying to turn. I believe it is jst the tup bolt of the plate.

194449 · Jul 27, 2011

You are turning the wrong bolt! Pop the center cap on the tensioner pulley wheel itself and turn the center bolt (probably allen or torx) in there clockwise (that's right). You are not trying to take the pulley off, but to move the pulley wheel arm in the direction that slackens it off the belt.

Go to your BMW dealer to get a replacement bolt for the hydraulic piece. No idea why you were trying to take that thing off.... Probably 50 cents...

[edit].... I retract everything. I misread your car type so I'll let the 540i people chime in. Ignore my post.

rph74 · Jul 27, 2011

The bolt you circled is the incorrect bolt! The bolt you need to loosen is lower and to the right of the circled bolt (at about 5 o'clock).

When you go to put the new belt on, you will need 2 wrenches going at once. There is a "fake" or cast bolt at about 4 o'clock in your picture (to the right and slightly lower of circled bolt) that uses a 17mm socket. You will use that fake bolt to apply tension (I used a long wrench because it requires quite a bit of force), and at the same time, you will tighten the 13mm bolt at 5 o'clock to lock the tensioner in place. Lastly, you tighten the other 13mm bolt that resides in front of the cast 17mm bolt.

It's actually very easy and intuitive once you've done the job.

16valex · Jul 27, 2011

Here is your pic but with correct circle on which tensioner pulley to rotate.

cn90 · Jul 27, 2011

http://www.bimmerboard.com/forums/posts/119957

bluebee · Jul 27, 2011

cn90 said:
http://www.bimmerboard.com/forums/posts/119957

To help others in the future, I added a reference to this thread in the canonical thread on hydraulic & mechanical tensioners, and, in the thread on the differences between mechanical & hydraulic belt tensioners.

- How to tell if you have mechanical or hydraulic belt tensioners (1) how to switch from mechanical to hydraulic (1) and what is the difference between the two types (1) (2)

Melrose · Jul 29, 2011

Yes the instructions are wrong in Bentley. You don't realize that there is a fake bolt welded to the plate. You have to loosen the bolt on top of that fake bolt first and then the one to the right. The arm will now move. Use the fake bolt with 17mm to tension it completely down, and lock it in place with the right hand bolt . Then go back and tighten the cap bolt on the fake bolt. It fooled me too. What a dummy uyou feel like.

Need help changing my belt - problem with hydraulic tensioner

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