My 4GTL has failed its MOT because offside rear brake is not working effectively. The handbrake works fine but the foot brakes are seriously imbalanced. The wheel cylinder is new-ish and does not seem to be leaking. With the drum off I can see that depressing the brake pedal makes the piston operate but obviously not enough. With the pedal depressed and the wheel jacked up it can still be turned relatively easily by hand. I have bled that brake. Hydraulic fluid looks clean and bubble free. To get the drum back on I back off the handbrake adjustor - is this a mistake? Should I just keep bleeding? I've done about 10 complete pushes of the pedal. Any ideas? Many thanks in advance.
- Thread starter Noswal
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mr-reno-139
AKA Paul Cunningham
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- lancing west sussex england
You say the piston moves they both need to push outwards equally the rear piston can seize as leading shoe does most of braking
if it was compensator problem the rrears would be equally low
if it was compensator problem the rrears would be equally low
Many thanks for these responses. It is just the off-side rear brakes not working properly. I do hope that it is not the regulator because, as you say Bobble, that does look to be tricky to take off. Both pistons definitely move and bleeding did improve the situation. I thought that I had pushed enough new fluid through to displace any air that might have been in the length of pipe between the regulator and the brake but maybe not.
mr-reno-139
AKA Paul Cunningham
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- 2,261
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- lancing west sussex england
when i took the yellow peril for an mot recently the brakes were low on one side but they also failed the flexi hose on the nearside after i change the hose having inspected the brakes themselves with no obvious faults the readings were much better maybe you have a restriction in the hose
that was not a fun job as the metal pipes had seized into the union
can't see how the compensator can send a different amount of fluid pressure to each rear wheel on that type of braking system
later cars not renault 4 do have a dual piston arrangement in the compensators and have had them seize on 1 circuit only
silly question you haven't got the leading and trailing shoes mixed up on that side with problem or has the adjustment not been set correctly as you have to completely release hand brake adjustments to make sure the lever arm inside the drum returns fully backwards and then adjust brakes themselves until drum just fits not sure what sort of brakes you have got as several different types of fitted
that was not a fun job as the metal pipes had seized into the union
can't see how the compensator can send a different amount of fluid pressure to each rear wheel on that type of braking system
later cars not renault 4 do have a dual piston arrangement in the compensators and have had them seize on 1 circuit only
silly question you haven't got the leading and trailing shoes mixed up on that side with problem or has the adjustment not been set correctly as you have to completely release hand brake adjustments to make sure the lever arm inside the drum returns fully backwards and then adjust brakes themselves until drum just fits not sure what sort of brakes you have got as several different types of fitted
mr-reno-139
AKA Paul Cunningham
- Messages
- 2,261
- Location
- lancing west sussex england
final thought it is possible that there is a mismatch between cylinder diametersif they were wrongly boxed or even from different suppliers maybe one is larger than the other if you can measure it if there is no other obvious problem can you post a photo of your brakes maybe we can spot something you have missed
Many thanks for this mr-reno-139. I did a lot more bleeding and, although I wouldn't say that the brakes are good, this has produced an improvement just big enough to allow the car to scrape through the MOT. I put the earlier problems down to poor performance on the part of my 'bleeding partner' (wife).