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big ives

Member Since: 24 Dec 2013
Location: Northern Ireland
Posts: 123

Brakes

Factory Defender V8 CSW 1989

Just past MOT last week

Only just started yesterday twice my brake pedal got spongy giving the impression no vacuum at the servo had to push the pedal to the floor to get her to stop then the pedal got hard again
Only happened two times yesterday doing about a 140 mile drive.

Already checked the following this morning: -
Hose to servo good vacuum no leaks and relatively new hose.
Pump brake pedal start engine pedal moves a little bit as normal.
No brake fluid leaks no loss of fluid.
All callipers rebuild over a year ago.
All wheel bearings checked no play.
Spin the wheels and all brakes operate (no engine running)
Also looking I have a G valve going to the rear wheels not a bias valve.
Can not see or detect/hear any leak at the servo pretty hard with the v8 running.

So, is my brake servo on the way out? Any other checks I can do to the servo?
Brake master cylinder?
Also does anyone have the part number for this G valve?
Can this G valve be replaced with the normal defender bias valve?

As always many thanks Ivan 2016 Discovery 4
1989 90 CSW V8 (fully rebuilt and running like a dream)
1996 defender tray back fully rebuilt/loaded for challenge events

9th Sep 2023 10:37am

big ives

Member Since: 24 Dec 2013
Location: Northern Ireland
Posts: 123

NRC 8215 found what i believe is the part number for this G valve 2016 Discovery 4
1989 90 CSW V8 (fully rebuilt and running like a dream)
1996 defender tray back fully rebuilt/loaded for challenge events

9th Sep 2023 10:48am

landy andy

Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5424

2006 Defender 110 Td5 USW Zermatt Silver

A spongy pedal wouldn’t have me looking at failed servo. A failed servo, or vacuum would give a harder pedal, with less braking effect I would have thought. Spongy pedal would be master cylinder, or the stuff you’ve checked like fluid loss, wheel bearings, expanding flex pipes.

9th Sep 2023 11:51am

big ives

Member Since: 24 Dec 2013
Location: Northern Ireland
Posts: 123

Sorry for the late response travelling back to work

Ok I will look at the master cylinder maybe time to replace it looks like it been on from the factory in 1989👍
For sure not leaking, no fluid in the drivers footwell

But better to replace

Many thanks Ivan 2016 Discovery 4
1989 90 CSW V8 (fully rebuilt and running like a dream)
1996 defender tray back fully rebuilt/loaded for challenge events

10th Sep 2023 10:17am

Dinnu

Member Since: 24 Dec 2019
Location: Lija
Posts: 3213

2012 Defender 90 Puma 2.2 CSW Santorini Black

Had a problem with my master cylinder that if brakes applied too gently, the non return valve would not close, and instead of pressurizing the system, the hydraulic fluid would leak back into the reservior.
No issue when applying the brakes hard/quick enough. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black

10th Sep 2023 12:36pm

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