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Thread: Removing M70 water pump

  1. #1
    Join Date
    Jun 2008
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    ontario canada
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    1991 bmw 850i

    Removing M70 water pump

    Just finished removing the water pump from my 91 850i and thought I would share the experience.
    After draining the coolant (mostly self drained from failure of offending pump) removing the fan shroud, expansion tank, radiator, fan, fan pulley, belt tensioners, hoses and a few other items in way of the pump you will come to the bolts on the water pump. You will have to remove the crank pulley in order to get at a single bolt at bottom of pump. You might think you need to remove the large center bolt but in fact no, just remove the six or so smaller bolts holding the pulley to the crank hub. No need to mark position, there is a dowel pin to relocate back in same place. It took a little careful prying and some penetrant but rest assured it will come off and then you can get at that last water pump bolt otherwise impossible to remove. Tapping, prying and using a few choice words of encouragement (threats) the water pump will now dislodge itself and the light at the end of the tunnel will suddenly blind you.

  2. #2
    Join Date
    Jan 2011
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    Oro Valley, AZ - USA
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    see my signature
    Nice write up, thanks!

  3. #3
    Join Date
    Dec 2007
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    Dallas, TX
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    '93 850Ci- Daily Driver
    That is definitely NOT how to remove the water pump.
    First thing to remember with these all aluminum engines and BMW in general: If you have to force something (either on or off) you are doing it wrong and will possibly damage something.

    The correct way to remove the water pump is by using three M5 bolts about 2" long. There are three holes on the pump itself that you thread these screws/bolts in and start turning them equally. What this does is to back the pump off the face of the engine - NO prying necessary, no penetrant required, takes about 2 minutes tops.
    If you are hard pressed to find three adequate bolts, the ones that hold the distribuotr caps in place can be used temporarily. Once the pump is off, the new one should just slip on.
    The danger in "prying" and "tapping" only increases your risk of damaging the water pump opening (leaks?).

    This is where a quick glance into the Repair Manual can save you time, headache and possible damage...
    '93 850Ci - Mineralweiss Metallic
    ALPINA B7 -Alpinweiss III

    BMWCCA E31 Chapter President



    ...the price of cool ain't cheap!

  4. #4
    Join Date
    Jun 2008
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    ontario canada
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    My Cars
    1991 bmw 850i
    Quite right TxGR8White. Thank you. The only reference I had available in the manual that was available to me made no mention of the jacking bolt method but now that I look at the pump housing I see them. Wrong or not gentle prying does not imply "forcing" any more than 'jacking" does although jacking is obviously far more controlled, easier and the intended method.
    I hope others can chime in to improve upon this procedure as well. Unless I was missing on my search of this forum there are only a few mentions about the procedure and nothing I found about the jacking bolts.

  5. #5
    Join Date
    May 2012
    Location
    Ohio
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    154
    My Cars
    1992 BMW 850i 6-Speed
    Hitting an old thread. I will be removing water pump soon. What grade of M5 bolts do you need to unseat the water pump? All I found in 2" was grade 8.8 at home depot and hit a few auto parts stores and they don't carry anything that long. Will these bolts be strong enough? Don't want the bolts to snap. Thanks for the help.

  6. #6
    Join Date
    Jul 2008
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    Northern WA USA
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    91 850i +++
    Use the 3 bolts that hold a distributor cap on, perfect configuration. They don't need to be especially strong, as they're working in compression only. Rotate around and keep them evenly tensioned.
    How come the middle half of any project always takes the most time?

  7. #7
    Join Date
    Oct 2008
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    Mt. Dora, Florida
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    Alpina B12 5.7, 850 CSi
    Quote Originally Posted by JBoggs8 View Post
    Hitting an old thread. I will be removing water pump soon. What grade of M5 bolts do you need to unseat the water pump? All I found in 2" was grade 8.8 at home depot and hit a few auto parts stores and they don't carry anything that long. Will these bolts be strong enough? Don't want the bolts to snap. Thanks for the help.
    I just got a set of them at Lowes a few weeks ago. After using them, I put them in a zip-lock bag, and labeled the bag: "DO NOT THROW AWAY - E31 WATER PUMP REMOVAL BOLTS". I had another set, but could not find them. What Bill (Maxlumens) said is right - put them in then go around turning them about 1 - 2 turns each in a circle. Also, remember DO NOT pull UP on the pump - just straight out. One of the pipes that runs down the valley has a small O ring that connects it with the valley pan cover. It is the pipe on the driver's side. If yo dislodge that O ring, you will have a leak requiring you to take everything off the top of the motor to get to. When putting on the new pump, lubricate the O rings with oil, and to align the two pipes, take your time - you can align them through the opening in the pump using a screw driver placed inside each pipe to guide them into position, then once they are initially seated, screw the pump in evenly all the way around. Good Luck.

  8. #8
    Join Date
    Aug 2007
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    Duesseldorf, NRW, Germany
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    Tire soap works better than oil on those rubber O-rings in my experience.

  9. #9
    Join Date
    Feb 2014
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    Auckland New Zealand
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    1991 850i
    You don't need to remove the fan shroud or the radiator to remove the water pump. There is just enough room to get the pump out the top between the shroud and the engine. Similarly the front engine pulley comes out the same at the bottom if I remember correctly. Be careful not to let tool or the front pulley hit the radiator core and damage it

  10. #10
    Join Date
    Feb 2008
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    Andover, MA
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    1992 BMW 850i/6 speed, 1990 BMW 750iL
    FYI to all, the 3 bolts that hold the dizzy cap to the head are the appropriate length M5 bolts. I have used them to back the water pump off the block.

  11. #11
    Join Date
    Aug 2007
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    Duesseldorf, NRW, Germany
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    '90 850iM70B54, '91 850i
    Quote Originally Posted by 850man View Post
    You don't need to remove the fan shroud or the radiator to remove the water pump. There is just enough room to get the pump out the top between the shroud and the engine. Similarly the front engine pulley comes out the same at the bottom if I remember correctly. Be careful not to let tool or the front pulley hit the radiator core and damage it
    If you love to work in really tight space leave the shroud mounted. Personally I hate the sharp edges of it and happily invest the extra 2 minutes to take it off.

  12. #12
    Join Date
    Oct 2018
    Location
    Los Angeles
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    1
    My Cars
    750iL- M70
    Currently working on one (750iL-M70). Everything looks good above, except the M5 bolts used to remove the pump need to be slightly longer than distributor cap bolts. 2" - as TxGR8White called out above should work fine. Be careful not to pull the coolant tubes under the intake manifold forward or backward when reinstalling. I usually mark then with a sharpie at the pump so I can keep an eye out for movement.

  13. #13
    Join Date
    Jan 2005
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    Japan
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    11/88 E32 750iL+98 E36M3
    For the M70 there is a detailed instruction to change the water pump here http://bmwe32.masscom.net/sean750/wa.../waterpump.htm
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