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Re: Cam tensioner leak -750 (archive)

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Posted by David Soo on December 24, 1999 at 12:19:28:

In Reply to: Cam tensioner leak -750 posted by Scott Mc on December 24, 1999 at 09:53:58:

: For those of you who have replaced the o ring on infamous the cam tensioner, a couple of questions.
: 1) Does orientation of the tensioner matter?
: 2) Is there a torque setting, or do you just load up the spring?
: 3) Do you need to bleed down or pump up system before removing or firing up?
: 4) Any upgraded materials? This is the third time mine has leaked (first time I will be doing the replacement).
: 5) Any other hints to make the job easier.

: Thanks,
: Scott McFarland
: Sacramento, CA
: 91 750il 98k miles

I replaced mine a year ago, so I may not remember everything now.
1. remove the air filter box in the front engin compartment (passenger side), the intake runners and the Airflow sensor.
2. locate the tensioner which is above the alternator and connects to the front part of the engin. it is cyclindrical in shape, ~1 inch in diameter and ~3 inches long
3. There is a black hard plastic cap at the end of the tensioner. Oil should be leaking from the hole at the end of this plastic cap. Remove the plastic cap from the tension. This may break the cap but this does not matters since it serves no real purpose anyway.
4. Use a long socket to remove the tensioner from the engin wall. The tensioner has a loaded spring inside and it may shoot out if the release is not under control.
5. The o-ring is inside the tensioner. I took mine to a Pepboys and found a 50 cents replacement (metric) I guess a SAE unit will work too.
6. To Put back the tensioner, make sure the roller seats on the chain properly. The roller is the part inside the block pushed onto the chain by the spring. You won't be able to see the chain but you can feel the roller if it is seated properly.
7. Push hard on the tensioner when you install it back in to the block. Once the tread catches, you are home free.

I am surprised to hear that you have replaced it three times. I have a '89 750il and the o-ring hardened after 10 years of service. Once I replaced mine, I have had no problem with it. Your mechanics took you money and did nothing!

Have fun. It takes one hour if experienced.

David Soo


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