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  1. #1
    JB007
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    belts for 850ciA (Brit needs help please)

    Hi. I need to change my drive belts as they havent been changed in a long time and show signs of cracking.

    I have searched the archives.

    I would like to have a picture of how the belts go around the water pump aircon pulley etc..

    I am a little confused as to whether or not there are two alternators for the V12. I can definitely see one big usual looking one to the right of the engine bay as you open the hood. Is the other alternator much smaller and to the left of the engine bay?

    I have fitted auxillary belts before in other cars but this one looks a little more complicated. I understand that once you know it takes around 10 mins. It helps if you take the fan off first and thats OK with me- I am just worried about which nut I have to undo first. I can see the tensioner which looks like a shock absorber. Can I change the belts from above or do I need to jack the car up and go fvrom the bottom?

    The 2 belts are 6pk x 1080 and 5pk x 1165 ribbed as I understand.
    thanks in advance


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    Re: belts for 850ciA (Brit needs help please)


    I hope this helps



    M70

    1991 BMW 850i 6Speed
    1997 BMW 850Ci
    1997 BMW 318ti
    1999 Jeep Cherokee Sport
    1974 Opel Manta Luxus


    Some days it's just not worth chewing through the restraints

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    if car has more then 40-50k miles since the

    belt/tensioner have been changed, order the tensioners too. They will not hold up the new belt. I changed the belts at 50k+ miles and the tensioner was so good I had to cut the belt off.
    I installed new belts and they would not fit, they were way too loose. Long story short the tensioner was gone... they are not expensive and a good insurance against belt failure.

    The pulley's are also weak, plastic ones are cracking over time and causing the belt to disintegrate.

    Contact Phoenix motorsport for a alloy pulley set - a bit on the bling side (they are flashy colors or silver) but as all items GerryUK makes, they seem very good quality.

    The only downside to the metal/alloy pulley's that they are supposed to be louder then plastic. I never measured the noise but I read once that it can cause a little extra noise.


    while you are there, change the hoses as well. They age and they start to go bad from the inside so by the time you see any imperfection its too late.

    not trying to suck you into a "while you are at it change the ... " game but these are inexpensive maintenance items which will fail anyway sooner or later. I like to change and fix things when they are still good and easy to just change an item instead of waiting when they fail and pay for a lot more then just a part (towing, rentacar, etc)



    1997 BMW 840CiA
    1990 BMW Z1
    2002 Astro Van AWD
    2003 Nissan 350Z Enthusiast Package
    1987 BMW 535i with 5spd manual
    1992 BMW 735iL
    2007 Mazda CX9 AWD
    1998 Yamaha Blaster+Breeze

    1995 850CSI CD00177 (SOLD)

  4. #4
    JB007
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    thanks but..

    I have this pic-although it looks nice but is still a little unclear.
    I cant see the alternator.

    Does the M70 have 2 alternators? How can I tell if my tensioners are no good? How do I check my pulleys? Am I looking for any play when I take the belts off?

    which nut (top or bottom) do I undo on the tensioner?

    A diagram and a dummys guide would be helpful.

    thanks Laszlo and el rojo.

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    Try this-----> (hope the link works)



  6. #6
    JB007
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    exactly what I was looking for! .............

    Thanks very much TxGr8White but what is this BS about a second alternator?

    I will buy the belts tomorrow and attempt to change the belts at the Bank Holiday weekend ( Extra Monday off as is a public holiday).


    Any ideas as to check the tensioners and pulleys to see if they need replacing- I am on 100K miles.

    Finally ,(if we just consider the lower tensioner) which nut do I undo? I think its the middle one and the one on the right on the pivot is the one to adjust the tension so no need for a prybar-am I right?


    once again thank you all and I hope to let you know soooooon.

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    some answers

    There is only one alternator. The other items driven by belts are the pentosin pump, the water pump, and the A/C compressor.

    Definately change the tensioners (in my opinion).

    You are correct about the "nuts" on the tensioner arms - one provides a pivot so that you don't need a pry bar - the other locks the arm in position.

    I found the job easier from below, so plan on removing the splash guard and jacking up the front.

    Good luck.
    Mark W in mid-MO
    2008 335xi coupe
    1993 850Ci 6-speed

    2 turbos ..................or 12 cylinders, no waiting!

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    in addition: there is a second alternator offered

    as an option on some euro (and possibly J-spec) cars. It is smaller than the one alternator and is located above the A/C compressor.
    When yo loosen the center nut, you will see a larger "nut" cast into the tensioner arm - this is where you attach ta second wrench to "pry" the tensioner to the full limit while tightening the outboard nut. Once the outboard nut is tight, tighten the center nut to lock everything in place. When tensioning the belts, you must put the tensioner in the farthest (tightest) most position in order for it to work properly and avoid belt slippage.

  9. #9
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    Re: in addition: there is a second alternator offered

    For reference, all J-specs came with the 2nd additional(32A) baby alternator.
    www.wuffer.net
    Langley, BC Canada
    91 E31 WufferRed CB72884 FrankenBimmer
    93 525iX Touring (wifemobile)

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    Also - Difference in A/C Belts

    Bought a new AC Compressor for my '91 850, the replacement
    had to have a different mounting bracket, a larger fan belt,
    and replacement of the A/C slippage sensor relay.

    This compressor and relay and belt was standard on later E-31's


  11. #11
    JB007
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    where isthe A/C slippage sensor relay located pls?


  12. #12
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    Re: where isthe A/C slippage sensor relay located pls?

    A little difficult to get to.

    It is under the drivers floor side. Have to remove the
    left speaker cover mat, (after the hood release handle & screw).

    On the left lower body side there are several screws holding
    a bracket which holds the mount for the relay. You have to
    remove the bracket screws, then you can get to remove/exchange the old for new relay (See the electrical manual on Wuffer's site)

    There were 2 relays produced, the old one would detect slippage
    signals from the old A/C compressor and cut it off until you
    shut down and re-started the engine.

    The new compressor will not run with the old relay because it
    does not send a signal to the relay ... Actually, it does nothing
    but tell the new compressor to run, slippage or not. But,
    the new compressor has a larger pully and belt, so I guess they
    did not need a slippage signal


  13. #13
    JB007
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    Thank you but......

    Is it possible to remove the clutch mechanism from the compressor without loss of refridgerant, in order to free her up with lubricant?

    Do you think that my relay could be bad? The pulley in my compressor moves ever so slowly but it did move at normal speed upon refilling with R134a gas for a brief period.

    many thanks

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    You have a leak in the system

    The compressor clutch will not engage if the refrigerant pressure
    is low, a switch disables it.

    The "O-Rings" where the hoses hook to the compressor are the
    first suspect place. There are 3 O-ring seals there,
    the long irregular shaped one is probably bad.

    Go to AutoZone or a parts store, or BMW, and get a replacement
    kit of O-Rings, with a little dexterity, you can replace them
    with the compressor on the car.

  15. #15
    JB007
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    Re: You have a leak in the system

    Hi. according to the a/c specialist I dont have a leak in the system. He used an expensive machine to first check for leak and then he filled with R134a + a/c lubricant so its a mystery. I will look further when I change belts this weekend and report back.

    best wishes and thanks

  16. #16
    JB007
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    Final update and slight help requierd please

    I have replaced both belts today. Couldn't get the fan clutch mechanism off and I know that its a reverse thread.

    Placed car on ramps. Took lower splash guard off. took off rad cowling plastic and hoses. Undid the two nuts near each of the tensioners.

    Then cleaned rollers with rag. The thing is that I had to use a prybar to push the tensioners and then tighten the 2 nuts again. Very strange as someone earlier mentioned that I do not need a prybar. The 2 nuts were normal type nuts and not one with teeth in as my old e30 has.

    refilled the coolant and started her up. I got a squeek for a few seconds as I thought that the belts were too slack and may need retensioning but squeek dissappeared and started again and no squeeks. i will try again tomorrow in daylight and report back.

    Also as my aircon compressor was not spinning, I decided to take off the clutch and possibly lubricate it. The centre nut on the clutchwas removed and the gasket came off in pieces. Cleaned it then oiled it with WD40 and used hylomar blue instant gasket and stuck the old gasket and put it back . Was extremely worried about the clutch wabbling as when I cleaned it 2 semi circlips came off . I think it must be one circlip which had sheared into 2 pieces and just placed it back and hoped that the aircon spins fast like it once did but it spins still albeit slowly-hopefully as I drive it may free up and spin fast- if not a new compressor followed by regas might be in order.

    I have a late 91 with R134a so dont know if an older compressor for R12 gas is OK from an old car or do I need a new type of compressor specifically for the R134a?

    sorry for the long post but its a R anmd R procedure for the belt replacement to help the next guy.

    The aircon clutch centre nut is 10mm.
    The tensioner attachment nuts were 13mm.
    The lower splash guard nuts were 8mm or 10mm.

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    Your AC compressor still needs some TLC

    I would not turn the AC on, based on your remarks. Broken circlips and disintegrated clutch material don't make for harmonious rotation. Here's how another guy with a V12 repaired his:


    AC clutch replacement

    Contact me offline if you decide you need another compressor. I have a couple of them from RHD cars; IIRC there's a different mounting situation because of the lines from the PS pump.

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    Re: if car has more then 40-50k miles since the

    I need to change belts and hoses on my Dakar M70 as at 90,000km I have never done so. Can you tell the address to email Phoenix Motorsport regarding the alloy pulleys ? Thanks :).........Ken

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