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Thread: Proportioning valve leak/replacement 1977 BMW 320 I

  1. #1
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    Proportioning valve leak/replacement 1977 BMW 320 I

    Hi guys I know there is another thread on this topic but I just wanted to start an updated version with a few other questions that I couldn't get an answer to off the other thread hope you guys can help

    So I got this leaking proportioning valve that I took out of my 1977 BMW 320 I and gave it a shot at cracking open the hex part. No luck sadly so I wanted to know if there are any aftermarket proportioning valves I can get for my bimmer. I'm not down to pay $300 for a new one since I will probably end up selling the car soon but if it's what I have to do then it will get done but I'm wondering if there is any aftermarket ones I could get for cheap instead?

    On the other forum the guys were talking about some adjustable proportioning valve that they payed like 50 bucks for and I wanna know where the hell they found it!!!! I need brakes again guys please help!! Or if anyone has came up with a way to crack open that hex thing on the valve it self. I'm guessing it's just some seal that needs to be replaced

  2. #2
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    Ski installed a new aftermarket proportioning valve.

    Page 76 of his thread - https://www.bimmerforums.com/forum/s...-thread/page76



    https://lmr.com/item/M2328C/Mustang-...rtioning-Valve

  3. #3
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    Unfortunately the leakage comes from the area that is mechanically pressed on, not able to be repaired.
    Should be pretty easy to pick up a used one. I have a spare one form my wrecked 82' sitting at home, unfortunately I won't be there for a few more weeks...

  4. #4
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    thanks guys im still pretty new with how a proportioning valve works but i read from that thread that the front lines dont pass through the proportioning valve? the guy i guess just ran the rear ones through and the front. can i do that with my car too? kinda confused with this prodimg.jpg

    - - - Updated - - -

    the picture is of the proportioning valve that i got. it has 2 holes for mounting it and 4 for the brake lines i believe. correct me if im wrong

  5. #5
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    If you just eliminated the proportioning valve, the rear brakes might lock up first in a panic stop.

    The proportioning valve reduces brake fluid pressure going to the rear. A pressure reducing valve analogous to what plumbers use.

    I think the OEM one is a little different, but the aftermarket ones are mostly just a spring loaded pressure reducing valve I believe. And you turn the hande to adjust the spring tension to change how much pressure reduction you get going to the rear brakes.

    Nothing goes to the front, nothing going in or coming out of the proportioning valve is connected to the front brakes.

    So if you have only one brake line going to the rear, and it T's near the rear axle, then just the one line goes through the proportioning valve. Then because it T's downstream from there, both rear wheels get reduced pressure.

  6. #6
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    Quote Originally Posted by Maxem25 View Post
    thanks guys im still pretty new with how a proportioning valve works but i read from that thread that the front lines dont pass through the proportioning valve? the guy i guess just ran the rear ones through and the front. can i do that with my car too? kinda confused with this prodimg.jpg

    - - - Updated - - -

    the picture is of the proportioning valve that i got. it has 2 holes for mounting it and 4 for the brake lines i believe. correct me if im wrong
    You are correct, It is only for the rear brakes.
    Since the E21 only has one brake line going to the rear, that proportioning valve may not work unless you plug one of the inlets and one of the outlets.
    The E21 proportioning valve is strictly a pressure reducing valve, where it only allows a percentage of full pressure to be applied to the rear.

    Some vehicles I have worked on have a style of proportioning valve that physically shifts brake pressure from the rear to the front up to a certain pressure. from the photo I am guessing that one is designed for rear only, but is for a style with two separate brake lines, one for each wheel. (typical for disc brakes)

  7. #7
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    Hi ...

    Are you saying that the 4 (or is it 5) port valve is the type mounted in your car ?

    Under normal circumstances, a proportioning valve is set up to reduce the amount of pressure going to the rear brakes depending on how hard the brake pedal is being pushed. This is to stop the rear wheels locking under heavy braking.

    As far as I can determine ... there were 2 types fitted to the e21 as OEM.

    I think it's the earlier type that has the 4(5) ports. This type has one of the brake lines to the front brakes routed through the valve. This allows the valve to "sense" if the front brake circuit loses pressure and fails. Losing front brake pressure allowed the valve to bypass the proportioning section and apply full brake pressure to the rear brakes as an emergency measure.

    Looks like the later models didn't have this "sensing system" ... you could fit a later type with only 2 ports and simply use a joiner to connect the existing front brake lines together.

    Going back the other way would involve connecting one of the front brake lines through the "sensing" part of the valve or the proportioning section would be bypassed all the time!

    Cheers
    Last edited by GDAus; 06-30-2017 at 12:23 AM.
    hmm .. Wonder what happens if I do this ...

  8. #8
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    http://www.pelicanparts.com/catalog/...pg4.htm#item18




    Oh, there may have been more than one type used, and one of them had a connection to the front brake tubing. That's news to me. Searching Pelican Parts for 1977 e21 proportioning valves shows both of these which look very different.

    http://www.realoem.com/bmw/enUS/show...diagId=34_0132

    http://www.realoem.com/bmw/enUS/show...diagId=34_0096

    Even the more complicated looking proportioning valve looks like it only has one line going through it?
    Last edited by okieflats; 06-30-2017 at 02:07 AM.

  9. #9
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  10. #10
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    Cool

    The proportioning valve(bmw 34341151640) e21's(75-83) use have one line in and one line out, I bought a new Ate for ~ $90 from an vendor from Italy and installed. They are around $130-150 new on ebay.



    http://www.ebay.com/itm/BMW-320I-BRAKE-PRESSURE-COMPENSATOR-VALVE-ATE-ORIGINAL-34341151640-/121238874406?hash=item1c3a666926:g:rdkAAMXQVT9Ss0Z T&vxp=mtr





    s-l500.jpg

    Randy
    Last edited by 320iAman; 06-30-2017 at 10:17 AM.

  11. #11
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    You're right Randy. That's the one to use. The OP may have something different since he has an early '77 and maybe those were different. I think I read in the other thread that they had one of the front brake lines pass though it. If so that is unnecessary.

    Anyway I have a used one like what Randy pictured I could sell if needed. I think it's good. From a parts car, but at least I see no evidence it leaked. Maybe I could test it?

    Oh, and do not buy an aftermarket proportioning valve because it would probably have the wrong threads. You need 10mm threads i think. 10mm diameter by 1mm thread pitch. Not SAE.
    Last edited by okieflats; 06-30-2017 at 09:49 PM.

  12. #12
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    ok guys sorry for the late reply no suprise if i get no answers but ya.

    SO...ive done some more reading and actually looked at the routing of my brake lines. out of the master cylinder there is two lines for the front portion of the car and one for the rear. One of the fronts leads straight to the passenger side wheel. the other goes into the proportioning valve that i had and out to the driver side. the rear line out of the master cyl runs through the prop valve and out as one line to the rear and t's off to both wheels.

    so... 2 inlets and 2 outlets. im trying to find an aftermarket valve and my question is can i join the front brake lines together and not run them through the prop valve and just have one inlet for the rear and one outlet? is that still going to lower the hydraulic pressure to the back in an emergency stop? or do i still need to run one of the front wheels through the prop valve? i need help finding the right after market prop valve for the cheapest prise. changing fitting and all that i can do if its the cheaper solution

    thanks for the replys and helping me out guys

  13. #13
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    You should convert to the newer style. One line in, one line out, pressure reduction for the rear only. I do not think your system is affecting the pressure going to the front. The front may just be "passing through" it. Or maybe the pressure to the front is somehow used to affect the amount of pressure reduction going to the rear. If someone definitively knows why the '77 has this 2 in 2 out proportioning valve I hope they enlighten us. But it obviously is not necessary because with the newer vehicles they went to the simpler one in one out rear only proportioning valve.

  14. #14
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    Cool

    Definitely get a new one and install, my brakes have improved much since installing a new one, the older one I took out was probably original. Brake masters I'm familiar with these cars have three lines-one too the left front caliper, one too right front caliper and one into the proportioning valve , from the valve goes too the back too the t-connector where the H Pressure is split too the left and right wheel cylinders, equal pressure in front and back brake circuits car stops fast and pulls to the left and right dont happen, new pro valve will get you into this area, renewing your brake hardware is a very good idea,,especially with the nuts that are allowed to drive on the road.

    I have renewed all the brake parts,,except the booster which is still good, braking is much better since I installed the new valve, and much more even in all brake circuits, a new valve will give your braking circuits a more equalized pressure, whereas a closed valve opening a little or being open too much or a leak will not.

    Randy
    Last edited by 320iAman; 07-15-2017 at 12:18 AM.

  15. #15
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    You guys are the best thanks I'm going to order an aftermarket one probably the willwood adjustable 1 line in one line out or some other type. I asked my toolcrip guy some questions about it and he said the same thing

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