Alternator belt replacement question

[awagnon]

I've asked this question on the 1150R and Sport Touring forums, but I'll ask it here also.

I've replaced the alternator belt on my 2002 RT a couple of times and tightened it according to the 1/4 turn rule. I went to buy a belt for my 2004 1150R tonight and the certified BMW tech warned about using that same technique. I was aware that BMW changed belts after 7/2003. I thought the only difference was length. However, he said there is a difference is stretch which requires the use of a an adjusting gauge he showed me. It goes between the two pulleys and pushes the alternator upward with a pre-set force from a spring. He said that is the only way to reliably set the tension. Anyone know if that's true or is the 1/4 turn setting still OK? Thanks in advance for any advice.

 

[BUBBAZANETTI]

POLY V vs ELAST belt. damned if i know the difference. i have a 99 which runs the old belt and when i replaced it, i just used the flex rule. 10,000 miles and no sqeeks, no problems. i always get a bit anal when i fix something, i want it to be just right. more likely than not, close to right is probably good enough. YMMV

at least i gave you some searchable terms.

 

[awagnon]

POLY V vs ELAST belt. damned if i know the difference. i have a 99 which runs the old belt and when i replaced it, i just used the flex rule. 10,000 miles and no sqeeks, no problems. i always get a bit anal when i fix something, i want it to be just right. more likely than not, close to right is probably good enough. YMMV

at least i gave you some searchable terms.

Thanks. Apparently some 2004 1150's have the old style belt and some the new ones. If the alternator pulley has a visible nut on the front, I think it's the old belt. If the pulley is flat on the front, then it's the new belt. The new belt number ends in ...41 and the old one ...79. According to the tech, you can't even use a torque wrench to set the tension on the new ones.

 

[bmwmick]

Thanks. Apparently some 2004 1150's have the old style belt and some the new ones. If the alternator pulley has a visible nut on the front, I think it's the old belt. If the pulley is flat on the front, then it's the new belt. The new belt number ends in ...41 and the old one ...79. According to the tech, you can't even use a torque wrench to set the tension on the new ones.

Al,
You just need to do a search on ELAST.

http://forums.bmwmoa.org/showthread.php?t=13439&highlight=elast

 

[BOXERR]

I think the new belt also has different pullies.
I fitted the updated belt to my R1100RS a few years ago, and I had to fit new pullies as well.

 

[awagnon]

I've read the previous thread and watched the movie, but it only applies to the old style belt. I still don't know how important it is to use the special tool to tension the new belts. I've seen the tool. It has a concave piece on each end that pushes against both pulleys with a pre-set amount of pressure when you turn a hex screw in the middle of the tool. I'm sure it would be too expensive to own. I guess I can take the bike to the dealer, but it seems a shame not to be able to replace an alternator belt. Like I said in my OP, I've done it a number of time with the old belt and torque wrench tensioning. In fact, you can use two nuts screwed together in place of the "tool" on the old tensioner, or an "acorn" nut if you can find one in metric.

 

[bmwmick]

The tool you are describing is for the new ELAST belt, not the older style PolyV belt.

 

[awagnon]

The tool you are describing is for the new ELAST belt, not the older style PolyV belt.

That's the way I was told, also. Apparently it sets the tension of the newer stretchy belts just right to allow the belt to stretch just the right amount. Supposedly they last longer than the old belt.

 

[bmwmick]

That's the way I was told, also. Apparently it sets the tension of the newer stretchy belts just right to allow the belt to stretch just the right amount. Supposedly they last longer than the old belt.

They modified the pulley on the alternator to be a one-way-drive freewheeling pulley.
That is how they extended the life.

 

[PMKALBY]

Hmmm.

So since the parts catalog shows the same lower pulley for pre 7/03 bikes and post 7/03 bikes, is it safe to assume that the belt's physical dimensions are the same?

If so, then is there any harm using the "regular" belt whose part number ends in 1779 on a bike that has the freewheeling pulley?

Because I'll bet you all dollars to donuts that when I picked up a new belt for my 04 at the dealer when I stopped to get my (stupid useless) state safety inspection, they didn't sell me an E-last belt....

 

[bmwmick]

Hmmm.

So since the parts catalog shows the same lower pulley for pre 7/03 bikes and post 7/03 bikes, is it safe to assume that the belt's physical dimensions are the same?

If so, then is there any harm using the "regular" belt whose part number ends in 1779 on a bike that has the freewheeling pulley?

Because I'll bet you all dollars to donuts that when I picked up a new belt for my 04 at the dealer when I stopped to get my (stupid useless) state safety inspection, they didn't sell me an E-last belt....

The old belt is a 4PK611 and the new ELAST is a 4PK592 The last three digits are the belt length in mm. Since the new belt is stretchy. You 'can' use the old belt but you will not be able to use the new tool. Clear as mud? Have your dealer reference SI 12 001 04 (003).
Some of the early engines (07/03) were equipped with the freewheel pulley but the OLD belt because of a supply problem. Adjust it like the old belt, 8Nm on the adjustment nut or 1/4 turn of the belt, midway between pulleys.

 

[PMKALBY]

Clear as mud?

Back to the dealer I go. I hate that dealer. Only went there because I needed that (stupid, useless) inspection. They didn't even ask date of manufacture of my RT.

I should have gone to the good shop first because as usual I'm going to end up there.

 

[awagnon]

I haven't looked at my 2004 yet. Do engines with the new belt and alternator pulley still have the tightening bolt on the left side? If so, I may just buy the old belt and adjust it the old way with a torgue wrench. ( Actually, the shop sold me one belt and gave me both with instructions to just return the one I don't use after I see what I have. It would be easy just to slip an old style belt on if the small difference in length didn't matter. )

 

[ANDYVH]

The more I read this type of post, the more I like my 94 R1100RS. I replaced the belt this spring, finally, after 100K miles. I marked the position of the alternator before removing the old belt, and returned the alternator to that position with the new belt. Now at 2000 miles since the new belt went in and no problems.

 

[BUBBAZANETTI]

The more I read this type of post, the more I like my 94 R1100RS. I replaced the belt this spring, finally, after 100K miles. I marked the position of the alternator before removing the old belt, and returned the alternator to that position with the new belt. Now at 2000 miles since the new belt went in and no problems.

yeah, this is pretty much how i did it too, i used the grime left on the alternator mount as an indicator, just returned it to the clean spots, hahaha

 

[PMKALBY]

I haven't looked at my 2004 yet. Do engines with the new belt and alternator pulley still have the tightening bolt on the left side?

I'll let you know once I do mine. I'm doing it ahead of schedule in about a week and a half so as to minimize the possibility of it failing during a big ride I have coming up.

 

[bmwmoose]

Poly V Belt Adjustment Video

Here is a link to a tensioning video,http://www.bmwmc.net/uploads/tm11/Poly%20V-belt%20sequence_medium.wmv