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mark1200



Member Since: 09 Oct 2011
Location: peterborough
Posts: 64

England 2004 Defender 90 Td5 HT Caledonian Blue
Brake servo
After 19 years of use i needed to change my rear brake discs and pads but i swapped the rear calipers too, as normal there are extras so the front discs and pads got changed as well, front calipers are only a year old. Here i am thinking that i now have shiney new brakes and there going to be a huge improvement but NO there almost useless, i know that they need to be beded in but i cant get the landy to stop. The brakes are bled properly and i have a good brake pedal bit it seems as if i have no assistance from the brake servo. The vacuum pump is working and the servo is holding a vacuum too. Question can a brake servo just fail instantly ? and its probably sods law for it to fail at this time. I have a new servo on order so i am hoping that will restore the brakes.
Post #988933 14th Apr 2023 12:27pm
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geobloke



Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4350

United Kingdom 
Yes the servo internals and/or the MC seals could be at fault here. If I were you I would change both ASAP.
Post #988946 14th Apr 2023 1:44pm
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mark1200



Member Since: 09 Oct 2011
Location: peterborough
Posts: 64

England 2004 Defender 90 Td5 HT Caledonian Blue
Update, new servo fitted today and no improvement. i know all the brakes are working as there getting hot but the l cant get the brakes to lock, there is no instant grab of the bakes only a gentle slowing. Thinking i need to remove all the pads and just check there not contaminated or glazed over. i cant think what else it could be ?
Post #989825 21st Apr 2023 2:48pm
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Dinnu



Member Since: 24 Dec 2019
Location: Lija
Posts: 3141

Malta 2012 Defender 90 Puma 2.2 CSW Santorini Black
When I do the MOT equivalent, the tester always says that the rear brakes are weak, and is something normal on a Defender. I know there is a proportional valve that reduces pressure, to avoid locking the rear brakes, which could otherwise spin you round in an emergency braking.

Keep in mind that there are brake pads with different coefficient of friction. Perhaps that could make the change. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black
Post #989834 21st Apr 2023 3:48pm
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mark1200



Member Since: 09 Oct 2011
Location: peterborough
Posts: 64

England 2004 Defender 90 Td5 HT Caledonian Blue
Update of all the things that have been changed. New discs and pads, new rear calipers, front calipers only one year old new servo, new master cylinder. goodridge flexi pipes and no air in the system. the braking was getting better but not as good as it was with the old brakes but yesterday i started to brake and the pedal went straight to the floor, pulled over and there is nothing obvious thats wrong, no leak brake fluid level is still on max. i am starting to get frustrated as to what is wrong as the old worn out brakes worked ok
Post #993275 19th May 2023 1:42pm
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geobloke



Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4350

United Kingdom 
Well you have change almost everything there is to change. May I ask how you bled the hydraulics?

It is possible if using the brake pedal pump method to damage the MC seals by pressing the pedal down to hard or fast.

Also the little o-ring seal between the MC and servo can fail to seat properly. I usually add a smear of RTV to the mating surface to dissuade any leaks.

I forgot to ask perviously whether you have ABS or not?!
Post #993276 19th May 2023 1:56pm
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geobloke



Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4350

United Kingdom 
Just thought of something else. When the calipers were installed are all the bleed nipples pointing upwards? It is possible to fit them upside down and then they will not bleed properly.
Post #993277 19th May 2023 2:04pm
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mark1200



Member Since: 09 Oct 2011
Location: peterborough
Posts: 64

England 2004 Defender 90 Td5 HT Caledonian Blue
i have a td5 90 no abs eveything is new oem kit no blue boxes lol. i dont want to name the brand of discs and pads but there very well known. i cant understand how with all the old kit the brakes were ok i only changed the discs as at the mot he said they were getting ready for a change, fair point. i have even gone to the trouble of rechecking that the new discs are seated on the hubs correctly the hub nut is set to the right tourqe of 150 ft/lb and there is no noticeable play in the wheel bearings. i have never had a vehicle that has taken so long to bed the brakes in and for the brakes to have poor stopping power but then for the pedal to go straight to the floor was a little alarming Shocked
Post #993278 19th May 2023 2:07pm
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mark1200



Member Since: 09 Oct 2011
Location: peterborough
Posts: 64

England 2004 Defender 90 Td5 HT Caledonian Blue
upside down calipers lol i think its almost impossible to fit rear calipers upside down as the solid brake line would not fit , but i take your point that mistakes can be made
Post #993279 19th May 2023 2:10pm
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geobloke



Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4350

United Kingdom 
Have no fear if the discs are Britpart. I have had a set of their drilled and grooved on the rear of Miffy and also the fronts on Phoebe (Freelander 2) are the same. Cannot fault them at all. Superb stopping efficiency and longevity.
Post #993280 19th May 2023 2:10pm
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geobloke



Member Since: 06 Nov 2012
Location: Nottinghamshire
Posts: 4350

United Kingdom 
mark1200 wrote:
upside down calipers lol i think its almost impossible to fit rear calipers upside down as the solid brake line would not fit , but i take your point that mistakes can be made


You would think. But it has been known to happen. Same as the clutch slave cylinder can be installed upside down.
Post #993281 19th May 2023 2:11pm
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TexasRover



Member Since: 24 Nov 2022
Location: Paris
Posts: 768

France 2002 Defender 110 Td5 DCPU Chawton White
I have worked on a vehicle once (volvo I believe) where I found the bleed nipple on the bottom of the caliber.

No idea how they bled them, but a simple swap put that right.
Post #993286 19th May 2023 2:45pm
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