![]() | Home > Technical > Brakes need pumping all the time |
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JulieG Member Since: 25 Jul 2024 Location: Scotland Posts: 3 ![]() ![]() |
OK, found the problem!
In the brake servo, there is the plunger/rod that goes into the master cylinder - it is this that drives the piston. It's held in place by a star washer/clip - turns out this was loose - so as the engine runs, the vibration causes the plunger/rod to shift about pushing the master cylinder piston down a little, leaving a gap between the plunger/rod and piston or diaphragm - thus after a bit when you press the brake, it has to take up this gap before it starts pushing the piston. I used a bit of tube, pushed the washer/clip hard into place, with the plunger/rod now fixed to the diaphragm it doesn't produce any gap. Took some finding! |
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landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5563 ![]() ![]() |
Great work
![]() ![]() Did you disconnect and remove the master cylinder to do this. |
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JulieG Member Since: 25 Jul 2024 Location: Scotland Posts: 3 ![]() ![]() |
Yes, it's a bit of a pain, because with the ABS modulator there isn't enough flex in the pipes, so it has to be removed completely (Inc bleeding the brakes etc).
You have to adjust the length of the plunger/rod to match the new master cylinder anyhow. So you end up removing and replacing it several times too long and the brakes lock on - unable to release, too short and there is excessive travel in the brake pedal. |
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landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5563 ![]() ![]() |
Thanks for that info.
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jst Member Since: 14 Jan 2008 Location: Taunton Posts: 7838 ![]() ![]() |
You can adjust the servo rod without completely removing the master cylinder. Undo the bolts from mc to servo and ease it forward. Depress the brake pedal so plunger/rod is protruding and then adjust. Its tight but doable, at least on the defensersninhave had. Cheers
James 110 XS Utility 130 Puma Station wagon/camper (in the making) 90 Puma Hardtop |
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