Thread: 300Tdi Defender Brake Overhaul. Now have problem

I know this is a bit long, but just trying to give the whole picture.


Work done :-
New calliper pistons, seals and pads.
New TRW master cylinder.
New fluid.
Power bled system.
Had good brake pedal, then pressure on it, start motor pedal moved down some.
Brakes working reasonably but I thought they should be better.
Forums say to look for cracks in servo booster, sure enough there they were alongside the master cylinder holding nuts.


Fitted new TRW servo booster and non return valve.
Bled master cylinder as in LR manual, then power bled to get any air out of pipes from master cylinder reconnection.
Good pedal height with a bit of flexing at the pedal but no movement to the floor.


Now the problem.
Hold down the pedal, start motor. Pedal does not move down.
Motor still on idle release pedal then press down and down it goes by 3 pumps its near the floor.
Motor off, release pedal, 1st pump pedal is good distance up from floor.
Driving along my long driveway, 20 Kph, knock out of gear and very little pressure need on brake pedal to stop quickly.
But put more pressure on the pedal and it starts going to the floor.
The same happens after getting up to 20 Kph and trying again.


Have tried taking vacuum hose off at he booster non return valve, motor on idle attached gauge and pump pulls 20" Hg vacuum steady, no fluctuation. So okay.
Can suck through the new non return valve but can't blow into booster. So okay.
Eased master cylinder back off booster, O ring looks to be seating okay.
Can't hear any noise from sucking vacuum leak.


Is it possible the new master cylinder has decided to have a seal problem??
Or is my new booster the problem??


Would appreciate any ideas. Thanks

Life happens and took me away from working on the Defender brakes.


A mechanic has had a win and I now have brakes.


He cleared the air from the front passenger line and calliper an got good height hard pedal but when motor running and thus booster working the pedal was going to the floor the more he tried the problem became worse, that is, pedal would go down quicker.


Another TRW mc was ordered and fitted but the same problem was there but not as bad.


In an attempt to get brakes the mechanic took the 1st mc to pieces and found small "cones" where the holes had been drilled through one of the plungers and was putting indentations in the shim washer that goes against it.


He took the internal metal parts from the old scored mc and installed them in body of the 1st mc using its seals.


Brakes now work.


2nd master cylinder was not taken apart as it has been returned for a claim as it appears to have the same fault developing.


Last year while in South Australia I had to replace a water pump I bought good quality but it only did 2,000 km and hard to be replaced.


It seems that spending money on what are supposed to be good quality parts doesn't ensure trouble free motoring.