Caledonian Chipmunks

Author Topic: Brake fluid leakage  (Read 218 times)

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Offline scchippie

  • Posts: 4
Brake fluid leakage
« on: Monday October 08, 2018, 17:48:12 UTC »
I have been fighting a problem with my right brake. When the temp gets below 60 F the brake leaks. During summer no problem. I have changed the o rings 3 times with the same result. Some have suggested I machine the grooves to accept round o rings instead of the standard flat ones. I have the standard dunlop brakes and would like to keep them. Any suggestions?


Offline john henderson

  • Posts: 269
  • Country: gb
Re: Brake fluid leakage
« Reply #1 on: Tuesday October 09, 2018, 10:04:35 UTC »
Its a long time since we converted to Clevelands (11 years), but I seem to remember weeping fluid as an issue with the Dunlops from time to time, and we seemed to be forever changing the seals.
Just a thought, if you are going to modify the Dunlops for different seals, the originality is surely gone, so maybe the Cleveland conversion is a possibility.  Ours has been definitely beneficial both in reliability and in the reduction in maintenance hours.
john h

Offline Dick Gower

  • Posts: 293
  • Country: au
Re: Brake fluid leakage
« Reply #2 on: Saturday October 13, 2018, 21:45:50 UTC »
The o-rings give far superior results Scchipie.

~ Dick
Dick Gower

Offline Tug

  • Posts: 2
Re: Brake fluid leakage
« Reply #3 on: Saturday October 13, 2018, 22:05:49 UTC »
We have had occasional problems with fluid leaking past the seals, we think this is due to the calliper bores being worn and failing to give a good seal, there is a modification to rebore and fit over size pistons end caps and seals. Think it is a Dunlop mod.

Offline rod brown

  • Posts: 2
  • Country: gb
Re: Brake fluid leakage
« Reply #4 on: Saturday October 13, 2018, 22:08:44 UTC »
If you go back to May 31 2006 in Technical Issues there is some discussion on Dunlop brakes and
Dick Gower has suggested some alternative seals for both Caliper and Master Cylinder.
If the caliper is leaking from the lower section you will probably find that there is some corrosion
in the bottom of the bore and Dunlop had a repair scheme to bore out and sleeve it back to .003"
oversize.  There is also mention there of a circlip problem allowing the piston to tilt and the seal to leak.
The parts book shows oversize seals, piston and friction pad.
If you cannot locate a replacement caliper I would try a three stone honing tool and clean it out to
.003" oversize and then either turn up a piston or locate the parts.
As a matter of interest the Portuguese Air Force used the Dunlop caliper with 'O' rings rather than the
square section and changed the hose pipe thread to metric.


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