Alternator belt tensioner

[wsanders123]

While replacing the water pump on my 95 M3, I decided to replace my belts as well. I go the A/C belt off with no problems, but when it came to the alternator belt (main belt), I basically stripped part of the tensioner. While using a hex socket to get some leverage on the tensioner, I managed to strip the tensioner just enough that I can no longer apply any leverage on the tensioner to take slack off the belt. I know, not a good situation.

The car has 65K on it so I am not sure that the tensioner itself needs replacement. Any ideas on how I can take the tension off the belt so I can replace it? How about removing the upper roller on the alternator bracket? (Fig 5 on page 121-6 of Bentley).

Thanks!

 

[manuel]

ouch! this is gonna be a tuffy. what you might be able to do is, cut the top of another bolt and weld it on top. use that turn the hex bolt. then just get a new one...but thats a poor man's idea.

 

[tablet]

Is this the first time you've attempted this task? Can you physically see what you stripped or is everything by feel only?

Reason I ask is because when I replaced my belts (328i 97), I used a 8mm allen for my AC and 16mm socket for the water pump/alternater pump. Yes...the tensioners were different in my vehicle. I initial thought that the previously owner had broke off an allen key in the water pump/alternater tensioner and I assumed this by feel. I didn't find out that it actually required a 16mm socket until I decided one day to visually inspect it with a flash light and mirror.

I hope this is the same problem. Otherwise good luck.

Ken

 

[wsanders123]

I will take a look with a mirror, but I thought along the same lines and tried to fit a larger socket over the engine belt tensioner. I am going by feel, but the larger socket did not seem to fit.

I cannot seem to find any instructions for removing the hydraulic tensioners in the Bentley manual. Is anyone familiar with how to do that for a six cylinder? If there is a way, I figure I might be able to cut the belt and just replace the tensioner part that I stripped with a new one.

 

[BigEarl325is]

I say it's just as easy just to buy a new tensioner. They're only like 30-50 bucks (don't remember exactly) If they ask it's the mechanical tensioner, not the hydraulic one (the M3 might be different but I doubt it) we have a hydraulic tensioner for our A/C (it looks like a little shock) but we have a mechanical one for our alternator water pump belt. It's only three bolts, you'll be able to feel it once you get the belt off. Just take the three bolts out, pop the new one in with the same three bolts and you're ready to go. If you haven't gotton the old belt off, just take a pair of tin snips and cut it off, then use the new belt of course. Hope this helps.

 

[wsanders123]

How can I submit a picture/attachment? I have a diagram of the bolt that has been stripped.

From what I can tell, my car does have hydraulic tensioners for both the A/C and engine belts. I am leaning towards getting a new tensioner, but am unsure of how to remove the tensioner and replace the problem bolt. Looks like there is a bolt between the tensioner and the idler pulley (upper roller) running through the assembly that I should be able to remove (this would be easier to explain with a picture). Easy? Difficult?

Thanks again.

 

[BigEarl325is]

Are you sure you have two hydraulic tensioners? They're both tensioners that looks like little shocks.

 

[flyinH]

the main belt should have a mech tensioner.there are 2 or 3 bolts that hold the tensioner on.once you get those off,the whole tensioner will come off.but like bigearl said,get the old belt off first.getting to those bolts with the belt on would be a serious PIA,plus the bolts would be under tension from the belt,making them difficult to remove.

 

[wsanders123]

I double checked and went into the dealer with my VIN, where they confirmed that I do have hydraulic tensioners for both the engine (main) and a/c belts. Got a few pointers on ways to tackle the job without replacing the tensioner, including how the dealer replaces the belts. They apparently don't even bother with leveraging the tensioner out of the way as described in Bentley by cranking on the tensioner bolt. As soon as I get some free time I will try it again and see how it works.

Thanks again.

 

[wsanders123]

Well, got the main belt off. I do have two hydraulic tensioners, so I basically got under the car, and pulled on the belt in two places. I pulled down on the belt running from the alternator to the power steering and then pulled out on the belt from the crankcase to the power steering pump. That basically leveraged the hydraulic tensioner out far enough that I could slip the belf off of the power steering pump. From there it was no problem completing the rest of the water pump, belts, thermostat and radiator hoses replacements.

Putting the new belt on worked pretty much the same way, I ran the belt around everything but the power steering and just pulled down from the alternator and out from the crankcase to leverage the tensioner out of the way.

It worked great! I didn't replace the bolt, although something like tap out might work to back the stripped bolt out. I figure I am good for several years, so we shall see for the next time.

Thanks for the help!

 

[BigEarl325is]

Wow, I am truly amazed. I guess ///M decided that the M3 deserved two hydraulic tensioners. I know my friend has a 95 325i and his belt setup is the same as mine (well not exactly, but he does have a mechanical tensioner)