DS21 rear brake lockup - again
  • Register
  • Help
Results 1 to 25 of 25
Like Tree3Likes
  • 2 Post By David S
  • 1 Post By tresbon2

Thread: DS21 rear brake lockup - again

  1. #1
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Icon5 DS21 rear brake lockup - again

    Today I went to test my car to see if a couple of new tyres had fixed the extreme shuddering problem at last.
    I barely got through my gates when the LHR brake locked up This has happened twice before. The first time chamfering of the linings fixed it. The second time I checked and adjusted the shoe alignment and found that the RHR brake was covered inside and out with a film of thin grease. I also replaced the cylinder o-rings although there were no leaks visible. I could only think that the oil/grease was from a faulty bearing seal.
    This time the LH and RH interiors are quite clean.
    My question is what can I do next and how critical is the shoe alignment?

    Don

    Advertisement
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  2. #2
    Fellow Frogger! citroenthusiast's Avatar
    Join Date
    Apr 2014
    Location
    Phoenix, Arizona USA
    Posts
    571

    Default

    If the shoes themselves are contaminated, it could cause them to grab. Consider replacing the shoes. Shoe alignment is not that critical, all that happens is the shoes will wear unevenly if you don't adjust the eccentric on a regular basis.
    Cheers,
    John T.

    54 TAV Legere; 61DS19 LHM BVH (son's); 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

  3. #3
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by citroenthusiast View Post
    If the shoes themselves are contaminated, it could cause them to grab. Consider replacing the shoes. Shoe alignment is not that critical, all that happens is the shoes will wear unevenly if you don't adjust the eccentric on a regular basis.
    Thanks John. The shoes show no sign of contamination and I have no idea how to fix this problem. In 60+ years of playing around with old cars I have had just about everything go wrong but never had this trouble with any other cars.
    Don
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  4. #4
    Fellow Frogger
    Join Date
    Jan 2004
    Location
    Sydney
    Posts
    8,965

    Default

    Have you considered the condition of the flexible hoses? Bad hoses with some internal failure could cause random behaviour.
    JohnW and Hotrodelectric like this.

  5. #5
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by David S View Post
    Have you considered the condition of the flexible hoses? Bad hoses with some internal failure could cause random behaviour.
    Thanks David. No I haven't thought of that and my local DS guru did not mention it either. I had been going to ask on this site whether I should consider replacing the hoses because I suspect they are 47 years old. I didn't because it was a no-brainer; of cause I should do it.

    Don
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  6. #6
    Now go make me a sandwich Hotrodelectric's Avatar
    Join Date
    Nov 2010
    Location
    San Diego, California, USA
    Posts
    3,488

    Default

    Quote Originally Posted by David S View Post
    Have you considered the condition of the flexible hoses? Bad hoses with some internal failure could cause random behaviour.
    Great suggestion. I've heard of it happening on "regular" old cars, didn't think it would happen on an LHM D.
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

  7. #7
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    SUCCESS! I should have checked it before but I simply adjusted the shoes as close as possible to the drums and that has cured the problem. Another lesson learned.
    Don
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  8. #8
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by tresbon2 View Post
    SUCCESS! I should have checked it before but I simply adjusted the shoes as close as possible to the drums and that has cured the problem. Another lesson learned.
    Don
    Woe is me. The lockup problem is back! It was absent for almost 100kms but today, following my cleaning the front brakes and deglazing the pad surface, I started on a test run but did not get further than the bottom of my driveway before the lockup on the same old wheel happened again. And I really do not know what else to do. A brake expert has told me that if it was caused by a faulty hose then the brake would lock on. In this case it releases as soon as I release the pedal.
    Has anyone else had this problem?
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  9. #9
    Fellow Frogger! citroenthusiast's Avatar
    Join Date
    Apr 2014
    Location
    Phoenix, Arizona USA
    Posts
    571

    Default

    It has happened to me from a leaky wheel cylinder. The LHM from the cylinder contaminated the shoes so when I rebuilt the wheel cylinder the contaminated shoes on that side really grabbed at the drum. In my case the problem went away eventually after I burned off all of the contamination (back then I was too cheap/poor to buy new shoes), but I did have to drive carefully for several weeks (this was my daily driver at the time).
    Cheers,
    John T.

    54 TAV Legere; 61DS19 LHM BVH (son's); 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

  10. #10
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by citroenthusiast View Post
    It has happened to me from a leaky wheel cylinder. The LHM from the cylinder contaminated the shoes so when I rebuilt the wheel cylinder the contaminated shoes on that side really grabbed at the drum. In my case the problem went away eventually after I burned off all of the contamination (back then I was too cheap/poor to buy new shoes), but I did have to drive carefully for several weeks (this was my daily driver at the time).
    It seems that I will have to take it to a brake specialist.
    I have one not too far away and I will drive extra carefully. I have noticed that there is no lockup in reverse, when the leading shoe becomes the trailing shoe and vice-versa.
    I think that I will have another look in case something is wrong with one of the springs, despite them all appearing normal last time I looked.
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  11. #11
    Fellow Frogger! citroenthusiast's Avatar
    Join Date
    Apr 2014
    Location
    Phoenix, Arizona USA
    Posts
    571

    Default

    One last thing to check is to make sure the front brakes are properly bled. Air in the front circuit could conceivably delay the application of the front brakes, leading to the appearance of the rear brakes locking up (when in fact they are just doing their job). Admittedly, this is a long shot since there would have to be quite a bit of air for this to happen, but at least it is easy and inexpensive to do....
    Cheers,
    John T.

    54 TAV Legere; 61DS19 LHM BVH (son's); 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

  12. #12
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by citroenthusiast View Post
    One last thing to check is to make sure the front brakes are properly bled. Air in the front circuit could conceivably delay the application of the front brakes, leading to the appearance of the rear brakes locking up (when in fact they are just doing their job). Admittedly, this is a long shot since there would have to be quite a bit of air for this to happen, but at least it is easy and inexpensive to do....
    Since my last post I checked the RH side brake and noticed that the shoes needed adjusting closer to the drums. I did not really think that this would fix the problem (it is only the LH side which locks up but releases as soon as I release the brake pedal) and it didn't.
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  13. #13
    Fellow Frogger! neural revolt's Avatar
    Join Date
    May 2005
    Location
    Frenchs Forest/Sydney/Australia
    Posts
    309

    Default

    Another long shot...
    I had a problem with a Renault Virage; one of the rear brakes would lockup in reverse but okay in forward motion.
    Was caused by the brake backing plate moving slightly when brakes applied. The mounting holes in the backing plate had elongated and no amount of tightening the retaining bolts would stop the movement. Had to weld up and redrill the holes.
    Past Frogs:
    Alpine White 1967 R10 (round eye)
    Alpine White 1972 R16TS
    Blue 1978 Virage Wagon

    Current:
    Red 2009 Clio RS 200 CUP

  14. #14
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Thanks to all for your ideas. I was getting ready to replace the brake hoses, just in case, but was not confident that this would help. So I had another go at adjusting the shoes as per the manual. The tolerances required are very small - .1 of a mm. Well so far (6km) so good. Now for a longer test.
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  15. #15
    Fellow Frogger!
    Join Date
    Apr 2016
    Location
    Bedford, UK
    Posts
    540

    Default

    There is a special tool for adjusting the rear brake shoe clearance. You can easily make one up. Have a look here:

    and maybe contact Colin Smith for dimensions etc.
    1968 DS21bvh Pallas in Gris Palladium

    Restoration blog: https://ds-restoration.blogspot.co.uk

  16. #16
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by Budge View Post
    There is a special tool for adjusting the rear brake shoe clearance. You can easily make one up. Have a look here:

    and maybe contact Colin Smith for dimensions etc.
    I made one after the first time this problem occurred. It was so simple even I could do it!
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  17. #17
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,048

    Default

    Why would the shoes lock up if the clearance to the drum is excessive? Or have they been over-adjusted all the time?

    Just curious.

    Cheers
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  18. #18
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by JohnW View Post
    Why would the shoes lock up if the clearance to the drum is excessive? Or have they been over-adjusted all the time?

    Just curious.

    Cheers
    I have no idea! When I adjusted the shoes the second time I also filed a bit more off the leading edge of the leading shoe. Maybe that is what did the trick -time will tell.
    JohnW likes this.
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  19. #19
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Adelaide
    Posts
    328

    Default

    Quote Originally Posted by tresbon2 View Post
    Thanks to all for your ideas. I was getting ready to replace the brake hoses, just in case, but was not confident that this would help. So I had another go at adjusting the shoes as per the manual. The tolerances required are very small - .1 of a mm. Well so far (6km) so good. Now for a longer test.
    Well, it lasted for almost 50kms but next time I started on a trip the lockup returned. So now I intend to change the brake hose, which from the history of this car is probably the original. I need a 9mm special spanner; the one like a ring spanner but with a bit missing to fit the pipe. I can't find any locally - can anyone suggest somewhere in Australia to try?
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

  20. #20
    1000+ Posts FIVEDOOR's Avatar
    Join Date
    Jun 2011
    Location
    Brisbane Qld
    Posts
    18,941

    Default

    Is this what you are looking for? I note the text says 8 and 9 mm but the image is of a larger one.

    SPANNER FLARE NUT METRIC 8MM X 9MM - JBS Tools
    Any day I wake up and don't have to go to work, is a good day
    Every day is a good day

  21. #21
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,048

    Default

    Quote Originally Posted by FIVEDOOR View Post
    Is this what you are looking for? I note the text says 8 and 9 mm but the image is of a larger one.

    SPANNER FLARE NUT METRIC 8MM X 9MM - JBS Tools
    Essential tool for an owner of a hydraulic Citroen!
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  22. #22
    Too many posts! JohnW's Avatar
    Join Date
    Jul 2001
    Location
    Perth, WA, Australia
    Posts
    10,048

    Default

    Original? Good grief! I had serious one wheel lockup on my Renault 4cv some years ago. It was 'only' a 20-year old hose, so far from original, which failed internally in such a way that a flap of rubber was acting as a one-way valve. I now use new hoses made by the local brake place, which has a truly amazing range of end fittings.

    Maybe the lockup, if internal failure, is related to the volume of fluid moving on brake application - very tight clearances means very little fluid to operate the 'valve' in the hose. drive a bit and the clearances will open up..... Just a thought.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  23. #23
    Fellow Frogger!
    Join Date
    Nov 2010
    Location
    Kapunda
    Posts
    420

    Default

    Go for a Snap-On spanner, definitely the best.(IMHO) and the dearest!
    Woody

  24. #24
    1000+ Posts forumnoreason's Avatar
    Join Date
    Nov 2010
    Location
    Ici.
    Posts
    2,307

    Default

    I'd be taking the brake cylinders off and having a look at the pistons and seals. I guess if the hoses are old you might be getting air in there but you'd be seeing fluid most likely. Other than there might crud in the lines, migt be time to take the rear height corrector off and give that new boots and a thorough clean. New brake shoes if they are getting thin or reshoe.

  25. #25
    bob
    bob is offline
    1000+ Posts
    Join Date
    May 2001
    Location
    Skipton
    Posts
    2,135

    Default

    G'day,

    a long long long time ago I had a '53 Customline, this also had a similar lock-up problem - but it wasn't 40 years old way back then...

    The local brake place advised to rough up the brand new lining with a rasp and drive through the "sensitive" time - it worked !!

    cheers,
    Bob

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •