2004 MCS, 67K, unmodified. I replaced the SC belt recently (routine maintenance, stock belt) and noticed oil all over the tensioner damper. It does not appear to be coming from the oil filter canister, or from the valve cover gasket; it appears to be coming from the SC damper itself. Is this common? Is the damper failing? When they fail, what's the worst that can happen?

Also, even with the new belt no holes are visible on the strap; is this normal?

 

You should have one hole visible. Double check to make sure the oil isn't coming from your motor mount. They are known to fail on a fairly regular basis. If it is your dampener in the tensioner assembly, the worse outcome is your belt snapping and the tensioner crashing into your crank pulley and wrecking it. The tensioner is about $125 and if you're handy, not too hard to replace. If not, expect about 1-1.5 hours labor.

 

The engine mount is not the source of this leak . . .

 

Tensioner #:

11287509476
http://www.realoem.com/bmw/showparts...94&hg=11&fg=18

 

Blazer, I can tell you, from personal experience, that when the tensioner fails, it can be catastrophic.

Prior to taking the v2 15% plunge, I thought I'd done enough research in possible consequences of doing the mod. Sure, I'd run across posts where the belts had failed, for whatever reasons, however, nothing seemed more serious than the inconvenience of it all. Just replace the belt and motor on.

In my post in the European regional section, I detail the results of my tensioner failure. The result was a €651 bill to cover the replacement tensioner arm, the replacement crank pulley, towing and labor. That's about $945 after conversion. As a result, a couple of the guys from the group down here have installed this strap ($28) from Minspeed, however, I now have this one from Detroit Tuned ($20). Regardless, either one of these stops would have saved me from €550 in repairs and I cannot recommend either one of them highly enough. I've got the bills to show for it. Hope this helps.

Cheers!!

 

That's why I stock tensioners and the DT straps.

 

Fluid loss from the damper does not mean impending disaster, the oil can get on the belt promoting slippage, and the arm will vibrate a little more. I had a tensioner strut without any damping capability for a long time; in fact I would guess many have failed dampers without knowing.


A strap/cable will help in case the belt breaks and it helps retain the strut's bushings that have a tendency of comming undone.

 

Thanks guys, but I'm still a little uncertain about one thing: Why, with a new belt, are no holes visible on the tensioner strap? What is it that is wearing out (or worn out) that accounts for this? And, has anyone found a source for the damper without replacing the entire tensioner assembly?

 

Which belt do you have on there?

 

stock belt from the dealer.

 

If I were you, I'd replace the tensioner assembly. My guess is the spring wears out over time.

 

At this point there are no replacement tensioner dampers available; the whole unit has to be replaced and with your mileage it is time.

Check the part number on the belt and verify it is correct, it sounds like the belt is too long. If you were to route it incorrectly it would be very loose. A worn spring would allow further compression (more strap) not greater extension.

 

What would be the source, at the dealer, of a belt that is 'too long' on a car with a stock pulley? I can imagine the dealer might have belts for 15% and JCW pulleys, but wouldn't those belts be shorter?

 

Yep, I got that backwards...

What does the dampener do on this piece anyways? I've taken the thing off playing with the different stops and haven't noticed it being compressed at all.

 

double check the routing.

 

Never mind...
I thought for about 30 seconds...no sleep last night

 

I did double-check the routing, but I seriously doubt that an engine with a mis-routed serpentine belt would run at all, not to mention one that has run as well as mine has, for 2-3,000 miles, without overheating, throwing codes, making noise, etc.

 

The problem you will have is belt slipping at the supercharger under high loads. Best case is 2 holes then as the belt stretches to have one and a half left over (about mid range). If you max out the tensioner you then under load can throw the belt off the pulleys. Find the problem that is giving you the slack if none look at getting a shorter belt.

 

Can the DT Strap be installed without removing the tensioner? Or at 75000 miles should I get a new tensioner when I do the belt?

Rich

 

I put a DT strap on my '03 S without removing the tensioner. I pulled the wheel and plastic arch for better access, and its still a bit tight, but it seemed like reaching up from below worked best for me. I suppose if I planned to replace the whole tensioner soon I'd do it and the strap at the same time time. Good luck!

 

Great. I was hoping that would be the case.

I am definitely going to do the belt in the spring. I have it already with the tensioner tool. I was trying to get an idea if people felt that at 75000 miles it was a good idea to replace the tensioner too just as a maintenance item.

Rich