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crunchy Off-Road Guru
Joined: 31 Jul 2003 Odometer: 1040 Location: Essex
1986 Land Rover 90nad
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Posted: Wed Dec 12, 2018 3:22 pm Post subject: '98 Disco 300tdi - failed MOT - rear brakes
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Just failed - tester thinks it may be compensator valve (?) - failed due to lacking in pressure at rears only.
Can anyone enlighten me on this or is there another likely culprit?
No signs of pressure loss, pedal firm but sinks on engine start up. Pads all good.
__________________________________ Max. |
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Winnet Difflock Royalty
Joined: 03 Dec 2003 Odometer: 14725 Location: Aberdeen
1985 Land Rover
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Posted: Thu Dec 13, 2018 10:07 am Post subject:
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That is the block that is mounted on the chassis just after the maters cylinder in the engine bay.
Are any of the pipes at the rear "crimped" in anyway so that they restrict the fluid?
G.
__________________________________ Bored......
All these questions and more after the tea break. |
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crunchy Off-Road Guru
Joined: 31 Jul 2003 Odometer: 1040 Location: Essex
1986 Land Rover 90nad
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Posted: Thu Dec 13, 2018 11:01 am Post subject:
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Thanks Winnett, I must admit that hydraulics are not my strong point - I will get under hopefully today to check it out - lacking an assistant to act as pedal pusher at present.
Can you explain more on this valve - is it standard fitment and is there any other possible component in the system or is this the one compensator/bias element? Guessing they do fail but I don't want to replace part by part in a guessing game due to severely depleted funds at present!
__________________________________ Max. |
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Winnet Difflock Royalty
Joined: 03 Dec 2003 Odometer: 14725 Location: Aberdeen
1985 Land Rover
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Posted: Thu Dec 13, 2018 5:02 pm Post subject:
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__________________________________ Bored......
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Winnet Difflock Royalty
Joined: 03 Dec 2003 Odometer: 14725 Location: Aberdeen
1985 Land Rover
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Posted: Thu Dec 13, 2018 5:09 pm Post subject:
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It is there to compensate for differences in the pressure required between the front and rear braking systems. As for standard, I haven't a clue given the way LR change things around and it depends on your setup.
There must be a restriction/blockage somewhere but if it affects both back brakes it it must be somewhere "common". There should be a flexi pipe at the rear so check it and the pipework, are you getting fluid there?
Apart from that there is only brake pipes that go to the engine bay and the valve/master cylinder so there isn't much to go wrong.
If you crack the bleed nipples does fluid come out?
G.
__________________________________ Bored......
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crunchy Off-Road Guru
Joined: 31 Jul 2003 Odometer: 1040 Location: Essex
1986 Land Rover 90nad
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Posted: Thu Dec 13, 2018 5:29 pm Post subject:
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Thanks for that - I had a good visual - all pipework looks very good. And got someone to stand on the brake pedal - again all good, flexible pipe from rear floor bracket to 'T' is fine it seems.
I have the Lockheed valve on NS inner wing.
I've now had both sets of pads out - I put in some thin packers and pressed pedal, then levered back the pistons (repeated again) = both sides and pairs of pistons are moving smoothly all the way in out - pads looked evenly worn, maybe slight glazing so I have cleaned/roughened that off. Discs look good, no ridge to speak of, clean/even wear.
I have not cracked the bleed nipples but given the smooth operation of the pistons I'm guessing it's getting through OK...
__________________________________ Max. |
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crunchy Off-Road Guru
Joined: 31 Jul 2003 Odometer: 1040 Location: Essex
1986 Land Rover 90nad
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Posted: Sun Dec 16, 2018 3:09 pm Post subject:
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Hi - anyone have any more thoughts?
__________________________________ Max. |
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crunchy Off-Road Guru
Joined: 31 Jul 2003 Odometer: 1040 Location: Essex
1986 Land Rover 90nad
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Posted: Wed Dec 19, 2018 7:55 am Post subject:
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Update: I pressure bled through with new fluid and that and the bit of fiddling with the calipers and pads and wahey! I got a pass. Not a huge amount better but enough now to satisfy the examiner.
The Disco lives on more borrowed time but at least I've got another year with the old girl.
Thanks Winnet for the advice and help.
__________________________________ Max. |
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dpcwright Just got MTs
Joined: 01 Feb 2005 Odometer: 191 Location: CAMBRIDGE
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Posted: Wed Dec 19, 2018 10:24 am Post subject:
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Whilst I understand your joy at passing the MOT test it should not be forgotten that the brakes are there potentially to save your life and that "just good enough" is not really adequate
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dpcwright Just got MTs
Joined: 01 Feb 2005 Odometer: 191 Location: CAMBRIDGE
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Posted: Wed Dec 19, 2018 10:25 am Post subject:
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Whilst I understand your joy at passing the MOT test it should not be forgotten that the brakes are there potentially to save your life and that "just good enough" is not really adequate
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crunchy Off-Road Guru
Joined: 31 Jul 2003 Odometer: 1040 Location: Essex
1986 Land Rover 90nad
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Posted: Thu Dec 20, 2018 10:58 am Post subject:
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Who said they were 'just good enough'? - they passed the test and in use feel more than adequate and pull up very well. As we all know the main part of braking is as the front but regardless these have have been fully tested and work perfectly satisfactorily.
__________________________________ Max. |
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stable Articulating
Joined: 19 May 2005 Odometer: 828 Location: Northumberland
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Posted: Sat Dec 22, 2018 11:31 am Post subject:
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The MOT does not test the pressure in the braking system. The rear brakes were just not putting enough resistance through the wheels to slow the rolling road enough. As you've discovered it's the calipers that are the issue. I suspect the 'figure of speech' used by the MOT tester has created a bum steer
I would be investing in some new calipers. Or, get genuine or G suffix seals and new stainless pistons and swap them for the old ones.
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