Bleeding Renault R12 Brakes
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  1. #1
    COL
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    Default Bleeding Renault R12 Brakes

    Hi Brains Trust

    I have just rebuilt the entire brake system of my R12 station wagon doing the following steps:

    1: Dismantled entire system drained old fluid, flushed out lines with mentholated spirits and the blew brake lines out with compressed air

    2: Honed the rear wheel cylinders and replaced the brake rubbers.

    3: Replaced the rear corrector valve.

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    4: Put new seal kits in the front calipers.

    5: Honed master cylinder and rebuilt with new kit, bled master cylinder on the bench, then re-install.

    I have used Castrol Bake Fluid Response Super DOT4.

    I have managed to get brake fluid through to all the bleed nipples expelling lots of air, but the brake pedal still goes to the floor. Also the brake pressure differential light comes on. So i must still have air in the brake system.

    What my question is, what are the tricks and methods others have used to bleed brakes?
    Regards Col

    1973 Renault R12 Station Wagon
    1976 Renault R12 Station Wagon
    2002 Renault Laguna V6
    1973 Alpine A110

    http://alpine-a110.weebly.com/

  2. #2
    1000+ Posts schlitzaugen's Avatar
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    I have explained this a number of times but not sure anyone actually tried it. Here goes again. It's the way I bleed all my brakes, including, yes you guessed it, my 1976 R12 GL.

    Get a brake fluid reservoir cap, put a hole in it, attach a hose to it, fill the reservoir up, put the cap with the hose on, attach the free end of hose to a tire valve. Open bleeding nipples in turn until no air is coming out anymore. Make sure fluid level never goes down.

    You need to be a bit inventive with the choice of fittings to the hose, but I trust your imagination. One hint, I use a BMW 2002 plastic cap because I found it seals perfectly on the R12 fluid reservoir. The end that goes on the tire is just a normal fitting used on tire pumps and such. With this method you don't actually need to bleed the master cylinder separately as all air is pushed out from wherever it is.
    ACHTUNG ALLES LOOKENPEEPERS

    Das computermachine is nicht fur gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitssparken. Ist nicht fur gewerken bei das dummkopfen. Das rubbernecken sightseeren keepen hands in das pockets-relaxen und watch das blinkenlights.

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    COL
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    Quote Originally Posted by schlitzaugen View Post
    I have explained this a number of times but not sure anyone actually tried it. Here goes again. It's the way I bleed all my brakes, including, yes you guessed it, my 1976 R12 GL.

    Get a brake fluid reservoir cap, put a hole in it, attach a hose to it, fill the reservoir up, put the cap with the hose on, attach the free end of hose to a tire valve. Open bleeding nipples in turn until no air is coming out anymore. Make sure fluid level never goes down.

    You need to be a bit inventive with the choice of fittings to the hose, but I trust your imagination. One hint, I use a BMW 2002 plastic cap because I found it seals perfectly on the R12 fluid reservoir. The end that goes on the tire is just a normal fitting used on tire pumps and such. With this method you don't actually need to bleed the master cylinder separately as all air is pushed out from wherever it is.
    Hi Schitzaugen

    I have an R12 brake reservoir cap with a fitting to go to my compressor regulator, that I made up many years ago. I can't really remember using it but I came across it tonight when packing my tools I was using today. I will give it a go and see what happens.
    Regards Col

    1973 Renault R12 Station Wagon
    1976 Renault R12 Station Wagon
    2002 Renault Laguna V6
    1973 Alpine A110

    http://alpine-a110.weebly.com/

  4. #4
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    Col,

    Here's my 2 cents worth...

    I had the same dilema with my r10 brakes and it turned out that a speck of crud had gone down the filler tube and jammed the master cylinder piston fully opened without me knowing it. The pedal still moved up and down as normal.

    In the end I removed the master cylinder and sure enough it was jammed.

    It took a while to figure it out but it sounds just like what you have.
    Every day when I wake up I reach up in the darkness with my eyes shut and if I cannot feel anything that resembles a wooden lid I know it will be a good day. No lid today.

  5. #5
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    Is the travel to the floor air or by-pass?

    Is it the early or late mastercylinder?

    Col what kit did you use to service the master cylinder?

    From memory there's a right and wrong way to re-assemble the MC

    Waht was the problem with the brakes in the first place?
    Daily Drivers: R10, R12, R17T(?) Decouvrable

    In the Shed(s):
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    In the Past:
    Dauphine X2, R10 X lots, R12 X2, R16TS, R17TS

  6. #6
    1000+ Posts schlitzaugen's Avatar
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    Quote Originally Posted by COL View Post
    Hi Schitzaugen

    I have an R12 brake reservoir cap with a fitting to go to my compressor regulator, that I made up many years ago. I can't really remember using it but I came across it tonight when packing my tools I was using today. I will give it a go and see what happens.
    That is a good start, but make sure the cap seals perfectly, and don't put compressor pressure in it. Just a tire inflated to normal driving pressure (approx. 2 bar).
    ACHTUNG ALLES LOOKENPEEPERS

    Das computermachine is nicht fur gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitssparken. Ist nicht fur gewerken bei das dummkopfen. Das rubbernecken sightseeren keepen hands in das pockets-relaxen und watch das blinkenlights.

  7. #7
    COL
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    Quote Originally Posted by Exfrogger View Post
    Is the travel to the floor air or by-pass?

    Is it the early or late mastercylinder?

    Col what kit did you use to service the master cylinder?

    From memory there's a right and wrong way to re-assemble the MC

    Waht was the problem with the brakes in the first place?
    Hi Exfrogger

    The corrector valve was leaking, so I replaced that and while I had the brake system apart, I thought I would drain the old brake fluid, clean the system and put in new brake fluid.

    The brakes worked O.K. but not as well as they should so I thought while I had the system apart I would change the brake rubbers all round.

    The kit I put in the master cylinder is the correct one. Its the later dual master cylinder.
    Regards Col

    1973 Renault R12 Station Wagon
    1976 Renault R12 Station Wagon
    2002 Renault Laguna V6
    1973 Alpine A110

    http://alpine-a110.weebly.com/

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    Hi Col

    At this stage how much fluid have you put through the system?

    Have you had someone pump the brakes while you watch what happens in the reservoir?

    P

    Daily Drivers: R10, R12, R17T(?) Decouvrable

    In the Shed(s):
    R8 (1.4 motor, 4 shock rear end), Dauphine, Pugeot 404

    In the Past:
    Dauphine X2, R10 X lots, R12 X2, R16TS, R17TS

  9. #9
    COL
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    Quote Originally Posted by Exfrogger View Post
    Hi Col

    At this stage how much fluid have you put through the system?

    Have you had someone pump the brakes while you watch what happens in the reservoir?

    P
    I have put approximately 800 mL into the system. I spilled a little on the shed floor when assembling the master cylinder, and would of bled out about 150 mL (just guessing)

    I have not looked into the reservoir with someone pumping the pedal, but i will check just to make sure all is O.K. (I have used new parts so all should be good)

    Will have another crack at the weekend
    Regards Col

    1973 Renault R12 Station Wagon
    1976 Renault R12 Station Wagon
    2002 Renault Laguna V6
    1973 Alpine A110

    http://alpine-a110.weebly.com/

  10. #10
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    Hi Coll

    Just checked what manuals I have and I do not have anything covering the later master cylinders.

    I'll assume that when you finished bleeding you were getting no air being expelled at the nipples. I'm almost out of ideas but these are my thoughts for they are worth:

    There are two components in the system that have been changed/serviced. I've replaced compensator valves and never primed them so I'm guessing they dont need it. The MC you said you primed on the bench.

    I'm hazy on this so you might need to cut me some slack. I think that when the brake compensator is fully depressed (closed) no further braking pressure is applied to the rear wheels (remember, one needs to bleed the brakes with the wheels on the ground). So, if the rear of the vehicle is lifted such that the wheels hang down and the brake compensator is fully shut (or the unit simply clamped shut) and the pedal still sinks to the floor, I suspect the is MC is at fault.

    Because the cylinder has been honed and a new kit installed I would want to determine if the pedal sinking to the floor is as a result of fluid bypassing the seals possibly split/nicked during installation or because of pitting, possibly exacerbated by honing. The only differential diagnoses I can come up with is to check if fluid is pumping into the resevior when the pedal is depressed. The other test is to see if the pedal holds pressure when it is "punched" or whether a light, constant pressure on the pedal causes it to sink to the floor.

    Is there any weeping of fluid at the back of the master cylinder?

    After that, Col, I'm done...

    All the best

    Ex
    Daily Drivers: R10, R12, R17T(?) Decouvrable

    In the Shed(s):
    R8 (1.4 motor, 4 shock rear end), Dauphine, Pugeot 404

    In the Past:
    Dauphine X2, R10 X lots, R12 X2, R16TS, R17TS

  11. #11
    COL
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    Default Update So Far

    Hi All

    Had another go at bleeding the brakes, got some more air out of the system.

    Can now push down the brake pedal applying lots of pressure, and the pressure differential switch is not activating.

    I still have a rather long pedal but that could be due to the fact that I have 54mm calipers from an R17 on the front instead of the 48mm standard R12 ones (had the R17 calipers on for the past 4 years).

    I'm still using the 19mm master cylinder, where as the R17 master cylinder is 20mm.
    Regards Col

    1973 Renault R12 Station Wagon
    1976 Renault R12 Station Wagon
    2002 Renault Laguna V6
    1973 Alpine A110

    http://alpine-a110.weebly.com/

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