Help Installing Engine Belts

I have undertaken to replace the pulleys, tensioners, and belts on my S65 and everything has gone smoothly up to the point of installing the new belts.

For quite some time yesterday I tried to install the alternator drive belt but could not manage to get it mounted on the tensioner pulley. Even after compressing the tensioner all the way, the belt would not slip on as it just did not seem to have enough slack.

I confirmed all of the part numbers and proper installation (i.e., tensioner arm, pulley, and belt), and confirmed that the belt and pulley are the same size as the old ones. But I just can't get that belt on the pulley.

Can anyone suggest any tricks or methods for doing this? Do you start mounting the belt on the underside of the pulley and work up & around? Or do you start on the top and work downwards? Should it be such a tight fit with the tensioner fully compressed? When removing the original belt I do not recall it being so difficult to take off the compressed tensioner.

I am at an impasse!

Check your belt routing (there's a different routing pattern for different model years - someone can chime in), check your part numbers, and make sure you yank that tensioner. When the tensioner is pulled as far as it should be, the belt goes on like a nice slipper. You don't need to take the tensioner off unless you want more work or are already replacing it.

I had the same problem but realized I wasn't pulling the tensioner hard enough. I remember there was something (a line or a bolt) that was blocking the travel of my wrench. So I had to use a breaker bar and socket with more clearance and pull the tensioner about 5 degrees more than I was before. I was scared I'd break something, but the tensioner rolled over slightly more and my belt went over the alternator easily.

Edit: if you see the pic below, there's a metal line to the left of the tensioner. You need clearance around that line to pull the tensioner as far as you can. Like the poster below said: the alternators the easiest last mounting point.

Double check the obvious first, that you have it routed correctly and the belt is on the inner (nearest to engine) track of the crank pulley. Then place the belt over the tensioner pulley in advance of pushing the pulley down with your wrench or ratchet and instead try to use either the alternator pulley or the water pump pulley as the final or last pulley you place the belt over to set it in place.

Thank you RedScytheM3 and Theodore!

I just got it on in a few seconds just now. After reading your posts I double checked the routing, and it was fine. Then I tried again with my breaker bar, short extension, and 14mm socket. Still no go so I checked for obstructions, as RedScytheM3 suggested, and noticed that the extension was hitting the oil line to the oil filter, preventing full compression of the tensioner.

After switching to a box wrench and going at it from the driver’s side fender, it compressed all the way and easily got the belt over the alternator pulley.

Thank you both very much! I feel foolish for not noticing the obstruction earlier (having spent a few hours trying to get the belt on).

rantarM3 wrote

Thank you RedScytheM3 and Theodore!

I just got it on in a few seconds just now. After reading your posts I double checked the routing, and it was fine. Then I tried again with my breaker bar, short extension, and 14mm socket. Still no go so I checked for obstructions, as RedScytheM3 suggested, and noticed that the extension was hitting the oil line to the oil filter, preventing full compression of the tensioner.

After switching to a box wrench and going at it from the driver's side fender, it compressed all the way and easily got the belt over the alternator pulley.

Thank you both very much! I feel foolish for not noticing the obstruction earlier (having spent a few hours trying to get the belt on).

Perfect! That's what the forum is for! Don't feel foolish the same thing happens to a lot of us. Glad I could help

I just order a set of acl bearings. Do these come with one for the top and bottoms or are they are all interchangeable? thanks

Angr2387 wrote

I just order a set of acl bearings. Do these come with one for the top and bottoms or are they are all interchangeable? thanks

search is your friend
https://www.m3post.com/forums/showthread.php?t=1490200&highlight=acl

I'm stuck, I've confirmed nothing is obstructing my wrench, it just simply won't go far enough to get the belt even close to going over the alternator, any tricks in missing

dsm2173 wrote

I'm stuck, I've confirmed nothing is obstructing my wrench, it just simply won't go far enough to get the belt even close to going over the alternator, any tricks in missing

You might have a short belt?
Incorrect routing?
Your wrench is unknowingly contacting something?

I used to struggle with getting the belts back on until I made this wrench.

Game changer.

The ac belt has been a giant pain in the ass. I used the biggest breaker bar I had to force the tensioner done and it took 2 people to get the belt started around the last pulley. I then had to use a pry bar and slightly crank the engine to get the belt seated. Took hours to get it seated fully. Not long after the bolt that holds the pulley on the tensioner sheared off(probably from me forcing the tensioner down so hard.
Any ideas? (Car is a 2010. Uses the double sided belt that runs under the PS pulley)
Currently using a single sided oreilys belt until I can get a new double sided and hopefully not break the new tensioner pulley and ruin another belt

Oreo Cat wrote

The ac belt has been a giant pain in the ass. I used the biggest breaker bar I had to force the tensioner done and it took 2 people to get the belt started around the last pulley. I then had to use a pry bar and slightly crank the engine to get the belt seated. Took hours to get it seated fully. Not long after the bolt that holds the pulley on the tensioner sheared off(probably from me forcing the tensioner down so hard.
Any ideas? (Car is a 2010. Uses the double sided belt that runs under the PS pulley)
Currently using a single sided oreilys belt until I can get a new double sided and hopefully not break the new tensioner pulley and ruin another belt

From my understanding you’ll need to get a whole new tensioner-pulley combo, or try to source the bolt and get the old one out somehow. I don’t think you can use a single sided belt because it drives other components with the other side of the belt-hence it being double sided from the factory

Oreo Cat wrote

The ac belt has been a giant pain in the ass. I used the biggest breaker bar I had to force the tensioner done and it took 2 people to get the belt started around the last pulley. I then had to use a pry bar and slightly crank the engine to get the belt seated. Took hours to get it seated fully.

I usually leave the tensioner pulley portion of the belt off and slip it on there.
When the belt is around the ridged pulleys, it gives slightly more room to compress the tensioner and slip the belt on. Trying to slip it over the crank pulley (or ac comp), usually won't work because there isn't enough slack.

But yea it's a tight fit.

Same with the alt/wp belt. You want to leave the tensioner pulley part of the belt off and slip it over there because it's a smooth pulley, vs the ribbed alt pulley which you'll have a harder time trying to slip the belt over.

Hard to explain but easier to show you in person if I could. I've done so many it's second nature to me.

rantarM3 wrote

Thank you RedScytheM3 and Theodore!

I just got it on in a few seconds just now. After reading your posts I double checked the routing, and it was fine. Then I tried again with my breaker bar, short extension, and 14mm socket. Still no go so I checked for obstructions, as RedScytheM3 suggested, and noticed that the extension was hitting the oil line to the oil filter, preventing full compression of the tensioner.

After switching to a box wrench and going at it from the driver’s side fender, it compressed all the way and easily got the belt over the alternator pulley.

Thank you both very much! I feel foolish for not noticing the obstruction earlier (having spent a few hours trying to get the belt on).

Hey guys,

I am having a weird issue. The problem is the Drive belt tensioner Pulley I ordered from FCP Euro came with a Torx bolt instead of the Hex bolt. It’s the BMW original part I am not able to use an offset wrench and not able to pull the tensioner all the way down to slide the belt in. I am using a T50 Torx bit on my breakerbar but the bit is long and hits the oil extension lines. .
Anyone run into this issue and any tips because there is no way I can get the belt on without pulling the tensioner all the way down…I really don’t want to deal with removing the oil lines just because of this. Appreciate any tips from the folks here…

M'EM wrote

Hey guys,

I am having a weird issue. The problem is the Drive belt tensioner Pulley I ordered from FCP Euro came with a Torx bolt instead of the Hex bolt. It’s the BMW original part I am not able to use an offset wrench and not able to pull the tensioner all the way down to slide the belt in. I am using a T50 Torx bit on my breakerbar but the bit is long and hits the oil extension lines. .
Anyone run into this issue and any tips because there is no way I can get the belt on without pulling the tensioner all the way down…I really don’t want to deal with removing the oil lines just because of this. Appreciate any tips from the folks here…

Figure it out? I’m looking to replace that pulley with their torx bolt pulley.

Well FCP Euro did confirm that part was updated. They recommended this tool:

https://www.fcpeuro.com/products/volvo-serpentine-belt-tensioner-tool-s60-s80-v70-xc70-xc90-cta-8760


But I rented the Serpentine belt kit from Autozone and ordered some low profile Torx bits and Sockets from
Amazon. Going to give it a try tomorrow..

M'EM wrote

Well FCP Euro did confirm that part was updated. They recommended this tool:

https://www.fcpeuro.com/products/volvo-serpentine-belt-tensioner-tool-s60-s80-v70-xc70-xc90-cta-8760


But I rented the Serpentine belt kit from Autozone and ordered some low profile Torx bits and Sockets from
Amazon. Going to give it a try tomorrow..

Well that’s annoying. Let us know how it works out.

I ordered this from Amazon

https://a.co/d/g9OZmqj

It worked like a charm. The bits are super low profile and fit in the offset wrench. I was able to clear the oil lines and pull the tensioner all the way down and slip the belt over the tensioner pulley. Job done! I dint even have to use the Kit I rented from Autozone.

One thing I would recommend is to put the belt on the tensioner pulley the last as it’s a smooth surface and the belt slides right on.

What I would recommend is to put down your purse first...

j/k...It is a PIA. The bolt head makes it harder but I have to put my body weight on it.

I always make sure the belt is seated on the ribbed pulleys and the belt is running over top of the ratchet. I turn the ratchet and slip the belt over the tensioner puller.

I got mine on, but at one point while trying to get the belt on (last part of the belt going over the tensioner) I snapped the bolt causing the whole pulley to just fall off. Really wish bmw made it more simple, I can take off the belt on my Tacoma with one hand.
Alternator died on the m3 last month and I haven’t even bothered touching it because I don’t want to deal with the belts right now

M'EM wrote

I ordered this from Amazon

https://a.co/d/g9OZmqj

It worked like a charm. The bits are super low profile and fit in the offset wrench. I was able to clear the oil lines and pull the tensioner all the way down and slip the belt over the tensioner pulley. Job done! I dint even have to use the Kit I rented from Autozone.

One thing I would recommend is to put the belt on the tensioner pulley the last as it’s a smooth surface and the belt slides right on.

Would you mind measuring the height of the T-30 bit from that set? I’d like to see if it will work for the oil filter housing removal (as opposed to cutting one down as most people seem to do). Thanks.

nick3753 wrote

Would you mind measuring the height of the T-30 bit from that set? I’d like to see if it will work for the oil filter housing removal (as opposed to cutting one down as most people seem to do). Thanks.

It’s 0.75 inches.

M'EM wrote

It’s 0.75 inches.

Thank you.