Much needed help and instructions on how to replace tensioner pulley
 

Hi,

My son's 92' 325i w/M50 engine is getting noisy from a dried out bearing on the tensioner pulley. I have the parts in hands, but lack of directions. Would some one point me to some instructions on how to replace the tensioner pulley on a e36 with M50 engine?

Thank you in advance.

Jay
SmileWavy

I have done this several times on my two e36s.

1) It is tight working in there. You will like yourself better if you remove everything that is easy to remove to give yourself more room. I have done the top one with the fan in place, but you will find it worthwhile to remove the fan to do the top tensioner. To remove the fan, you need to remove the air filter housing and the cover over the radiator, and you need to make a tool that holds the bolts in the fan pulley so you can hold it still while breaking the fan loose. The tool is a piece of steel strap about 1/8" thick and 1 1/2" wide from the hardware store. Drill two holes in it that will fit over the heads of the 10mm bolts in the pulley. Note that the bolts through that pulley are in a rectangular pattern. You will have to grind a notch in the side of the strap between the holes to fit around fan shaft. This takes a while to make, but you will find that lots of jobs are easier with the fan off, so you will use your new tool often if you have it. The fan is LEFT HANDED THREAD.

2) The bottom tensioner is the one that fails most often. It is held on by an allan screw. That screw is very tight. A good quality socket-mounted allan wrench is a plus. A pair of channel locks will twist the tensioner to release the tension on the belt so you can slip the belt off.

3) While you are in there, replace the belts. Also, look for evidence of cooling water leaks from the bottom of the water pump and the thermostat housing. While you have the fan and belts off is a good time for some maintenance on those items if they are due.

M50 Tensioner
 

The top one which tensions the alternator, waterpump, powersteering belt is pretty easy to replace. Remove the air filter box and disconnect the air temp sensor that mounts in it (10mm socket) (I cover the sensor with a plastic cap while it is exposed) and set the box aside. The tensioner is visible then. Pop off the dust cover with a little screwdriver and you can remove the pulley with a 16mm socket. Turn clockwise to release the belt after you review the belt path.
Replace the pulley with the new one, and put the belt back in place. With your droplight examine the belt on all its pulleys to be sure it is properly seated before you start the engine. Remember to snap the little dust cover back on.

You can run the engine with the air filter off to verify all is OK and listen for any other noises. If all OK, reinstall the filter box and you're done.

If you are changing the one for the AC compressor, you will need to take the fan off.
I usually just pull the radiator if I am going to be doing work on the stuff from thermostat housing on down. Much easier to remove things without breaking stuff.

Be careful removing the fan when it has been on a long time. The nut may be very tight and if you use too much leverage, you can slip and can break the plastic t-stat housing and the plastic fan pulley. I've replaced mine with aluminum parts.

Thank you guys!! I have ordered the tensioner with pulley and the off-set pulley (?), I will replace them as soon as I get them.

Again, thanks!!

Well, I managed to get top tensioner pulley off with much effort. I also managed to removed the middle pulley with the fan and the radiator on with a heavy duty allen wrench. However, when I bough the pulley, I managed to ordered the pulley for the mechanical vs. the hydraulic one, so I have to buy one locally, which is outrages price. Oh well, live and learn.

Here is the question. Do I have to remove the entire hydraulic tensioner to mount the pulley back on or I can just do it from the car?

You guys were right, the one is bad is the middle one.

Thanks,

Jay

You don't have to remove the tensioner. I had never removed one until last weekend when I noticed that there was lateral play in the tensioner hinge and I pulled it off to see if I could figure out where the play was coming from and whether I could correct it. Once the belt is off, just three easy bolts and it comes off.

I could not figure out why mine had lateral movement. I overtorqued the bolt through the hinge bearings and got rid of a little bit of the play without affecting the hinge action of the tensioner.

All back together now - No more bearing noise at all. I replaced the idler pulley and the tensioner pulley. Oh, and I did replaced the upper radiator hose since I saw it got pinched from the clamp.

Now, I am on the next maintenance item and the last item, which is the transmission fluid. I guess, I will head into the Tech Info Center to read up on "how to" section for this task.

Any other suggestions, please feel free to share.

Thanks everyone for contributing to my success with the pulleys swapping.

Jay