belts, tensioner, and idler this weekend

I noticed a little something a couple nights ago when I was tucking my car away for the night. A little extra noise that shouldn't be there. I got out the stethoscope and found the main engine drive belt tensioner (mechanical) was making some noise. As most of us here know, the BMW dealers cannot get the mechanical tensioners any longer, so I ordered a new tensioner, idler pulley, and both drive belts from oembimmerparts.com. I think I have a project for the weekend now. I might regret it later, but I didn't order the AC belt tensioner.

I thought about replacing these pulleys when I had the car apart for the oil filter housing, but decided I needed to save a few bucks since they weren't making any noise yet. That was short lived.

I also ordered a transmission filter, but I probably won't get around to doing that this weekend.

oembimmerparts.com did it again
With the free shipping option, I had my order in less than 48 hours. They have great prices and great service. I know this sounds like a shameless plug, and to some extent it is. I'm just a satisfied customer. They did the same thing last month when I ordered a radiator and brass bleeder screw. They're terrific.

I'm hoping I can sneak everything in and out without removing the fan and shroud. I think I can do it if I just remove the power steering fluid reservoir.

The AC belt is a walk in the park. Remove splash guard, un tension tensioner, put clip (or small metal dowell) into the lock holes on the tensioner to hold it in place, remove the 2 bolts, and install the new one, remove the clip and your done. I just did mine a week or so ago. It started with the top idler roller, replaced that and then everything else went to hell. I had to remove the idler to get to the waterpump tensioner. I think all in all it took me about an hour.

Edit: I removed the fan, and the one end of the upper radiator hose (radiator end) and moved it out of the way. It can be done without removing this I am sure, but boy it was easier to get the fan off with that out of the way. Expecially when you are using channel locks to remove the fan... Came off without a fight tho. Best of luck!

I too just did my idler and tensioner recently. Just removed the fan and airbox and moved the shroud to the driver side after removing the small expansion tank hose. My ac tensioner needs to be replaced but I will wait for spring time. With new rollers, my motor no longer dips below the idle mark during shifts. Agrred with Nine6, ac tensioner should be easy from underneath the car. Best part about that DIY is that I discovered that one of the mounting bolts for my alternator had almost completely backed out. I would not have noticed this if I did not have the belts off with a clear view of that area.

I would do them all in one shot.

haha...I'm doing the very same thing tomorrow. All new belts, tensioners plus oil filter housing gasket, new disa unit, cleaning MAF and icv. Looking forward to it and I hope it will be stress free. I'm going to give it a shot without removing the shroud so I will have to get underneath for the ac tensioner. This afternoon I'm doing valve cover gasket and new NGK spark plugs. Happy wrenchings!

My DISA just took a dump... Domino effect...

Can a misadjusted tensioner cause the engine to idle too low to run? I did a recent repair in which I needed to remove the belt to access the power steering. I did notice that the tensioner spun once or twice with a "click". I couldn't get it to spin back to the original lock position but I put the belt back on anyway. Now, I'm having some issues: Check engine light, very low idle to shut off. Strange sounds...

AsymMetric - No. There's not really much of an adjustment to the tensioner. It's automatic. Even if the pulley bearings seized, the engine would still run for a little while. The belt would just slide over the pulley until it broke or shredded.
Are you referring to the little tooth that's on the idler pulley mount that is supposed to fit into the mounting point so that the pulley is aligned correctly? If so, you need to remove the belt, loosen the bolt, line up the tooth with the space where it's supposed to fit, and then tighten and reinstall it.

I just finished my installation. I remove the airbox and moved the PS reservoir out of the way. I also removed the fan from the water pump pulley, but left it in the shroud. I did not remove the shroud. This gave me enough room to work and it was actually pretty easy. The idle is is much quieter now.

Originally Posted by vavet5308

AsymMetric - No. There's not really much of an adjustment to the tensioner. It's automatic. Even if the pulley bearings seized, the engine would still run for a little while. The belt would just slide over the pulley until it broke or shredded.
Are you referring to the little tooth that's on the idler pulley mount that is supposed to fit into the mounting point so that the pulley is aligned correctly? If so, you need to remove the belt, loosen the bolt, line up the tooth with the space where it's supposed to fit, and then tighten and reinstall it.

I just finished my installation. I remove the airbox and moved the PS reservoir out of the way. I also removed the fan from the water pump pulley, but left it in the shroud. I did not remove the shroud. This gave me enough room to work and it was actually pretty easy. The idle is is much quieter now.

Glad to know your install went well. I had to postpone mine after getting.so busy all day. Good to know I won't have to remove the shroud for this. There seem to be other opinions that there isn't much space to replace the tensioners with it in place. I dont want to do more than I need for this project. Next spring I will replace the waterpump, thermostat, expansion tank, radiator and hoses.

So how tight do you have to get the belt when re tightening the tensioner, is it one of those things where you need a second set of hands to pry on it when you tighten the bolts?

BMW belt tensioners are all self-adjusting (spring loaded). You just bolt them on and pivot the arm far enough to slip the belt on, then release the arm.

Ok thanks.