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LR 90 brake system fault finding.


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Hello, got a LR90, discs on front, Salisbury axle with drum brakes on the rear.

I've just re-built both axles, front has new discs, calipers and pads, rear has just had new shoes.

Before I took it apart the brakes where positive but only at the very bottom end of travel of the pedal - I put this down to the rear shoes being worn and the snail cams not being adjusted properly.

Took it out for a test drive lats night and its doing the same thing after I had adjusted the snail cams etc. not had chance to re-adjust after my drive, but somthing I did find odd was when I was pumping the pedal by hand every so often on a stroke down it would feel like it was hitting a mechanical stop, then the next pump it would just be normal.

I can pump the pedal up, but it wont stay hard - when engine is not on, you can keep pumping the pedal, but it looses its firmness - is this normal?

I have no leaks that are pissing oil, so I'm starting to think its the master cylinder? What would be symptoms of the brake servo going?

Note: the master cylinder is STC441, 3 ports one pointing down, the other two point at the 2 o'clock position. Servo is STC442 the thin one with vacume port at 2 o'clock position.

Cheers

Mav

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If I correctly understand your description, then yes it seems the brake master cylinder is at fault.

It is often more practical to replace the master cylinder as a complete unit, than put a kit through the old one.

I am a retired mechanic now,, but would get very frustrated with brake faults where others have fitted wrong sized brake shoes, or topped up the brake reservoir with conflicting fluids that create gas bubbles in the lines..

I once had a clutch issue to deal with, only to notice the clutch master cylinder filler cap was on its side.!

Some idiot had the bright idea that another manufacturers master cylinder would work being cheaper, even though you had to park the vehicle on the side of a cliff to top it up. True story.

This being said look for past genius repairs and if all is ok, just replace the brake master cylinder and do not stop for anyone. ;)

Regards Phil......

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If I correctly understand your description, then yes it seems the brake master cylinder is at fault.

It is often more practical to replace the master cylinder as a complete unit, than put a kit through the old one.

I am a retired mechanic now,, but would get very frustrated with brake faults where others have fitted wrong sized brake shoes, or topped up the brake reservoir with conflicting fluids that create gas bubbles in the lines..

I once had a clutch issue to deal with, only to notice the clutch master cylinder filler cap was on its side.!

Some idiot had the bright idea that another manufacturers master cylinder would work being cheaper, even though you had to park the vehicle on the side of a cliff to top it up. True story.

This being said look for past genius repairs and if all is ok, just replace the brake master cylinder and do not stop for anyone. ;)

Regards Phil......

Cheers Phil, after some deliberation, I've come to the conclusion it must be the brake master, I'm loosing pressure somewhere, as seen as its non of the caliper components or lines it must be leaking past the seals in the master cylinder, ordered a new Lucas one today. all being well that will solve the problem.

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  • 2 weeks later...

Got round to changeing out the master cyclinder last night... It certainly fixed the problem! I've never felt brakes like it, its awesome. The more frightening thing in I belive the front part of the master cyclinder was bipassing totally, so when it was on the road there was only the rear brakes operating... From initial inspection of the old master cylinder, it look like water ingress has caused the barrel to corrode on the inside, tearing up the plunger seals for the front brakes! not so good.

Now pumps up holds pressure like it should. job done.

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