Broke My Brakes

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.

instantsquid

New Member
Posts
1,362
Location
Tadley, Hants
Went to my first "Pay-n-Play" yesterday and got my 1988 Ninety sill-deep in very thick mud. When I got home I took each wheel off and jet-washed all the crap off. At the back I also took the brake drums off and cleaned the mud from inside the drum and all around behind the shoes, etc.

Driving to work this morning, brakes still not feeling brilliant - I guessed the pads and shoes were still a bit contaminated, so braked a bit harder a few times. The feel did improve a little but still not quite right.

Driving home I got the impression that the brake pedal was going down further than normal. I didn't do anything silly while I was driving, but when I got home I pumped the pedal a few times, and sure enough it "pumped up". However, constant pressure on the pedal and it slowly goes back down again.

I'm thinking master cylinder failure.

I don't appear to have lost any brake fluid - the level in the reservoir is still good.

What I can't work out is whether the failure today is coincidence, or is in some way connected to yesterday's "mud plugging". I really can't see how it could be related, but I generally don't believe in coincidence!

Any ideas? Is my diagnosis correct?

Ian.
 
Same happened to me, but I'm pretty sure it was a slave cylinder. Guy who fixed it said it was common for them to go.

Mine also happened after a p n p day, so perhaps it is connected to using the brakes with more effort?
 
i would check and then bleed rear cylinders first
Is it worth having a pair of cylinders ready just in case?

Although I used a jet-wash for cleaning, I was careful not to blast the cylinders themselves as I seem to recall reading that it's possible to push water past the seals.

Can I ask why the rear cylinders would give the symptoms I've experienced? (Not trying to be difficult - I'm genuinely mystified!)

Ian.
 
calipers are more tightly sealed wouldnt be difficult for rubber gaiter on cylinder to get full of silt or water cotaminating fluid or wearing seal
 
It sounds like you've got air in the system and it needs bleeding.

The fact that it's happened just after a pay and play and a jet wash would make me think to check the tubes and hoses for corrosion. It's possible that you've blasted a microscopic hole in a bady corroded part of a tube.

I just had to replace the front to back tube on mine as it was picked up as badly corroded in one place in the mot. It acted the exact way you describe before i bled it properly. Pump it up and it feels good, leave it about 20 seconds and the pressure drops dramatically.

The level didn't really go down either, just the pressure.
 
Okay, easy diagnosis for you now....

The brake pedal only "pumps up" with the engine running. With the engine off, brakes are solid and the pedal doesn't slowly go down. Start the engine and immediately it's possible to push the pedal down all the way, and then it can be pumped to get it back up.

So...... knackered servo?
 
Ian, I'm sure not a fool proof way of checking, but one easy way to check the servo and the brake system for leaks is to turn the Landy off and pump the brake pedal. Every time you depress the pedal you should feel the pedal "height" come up and the pedal get harder.


After a few firm pumps of the pedal, hold it down. Leave pressure on the pedal for 20 seconds or so. Does the pedal move slowly (or quickly) to the floor? If so then there is a leak somewhere in the system.

Keeping pressure on the brake pedal, start the vehicle. Does the pedal drop slightly? It should due to the power assisted vacuum kicking in as the engine starts to run.
 
Last edited:
I'm not able to get the pedal to go down to the floor with the engine off. But once the engine is running it does go down. I can then "pump up" the pedal - but then with a constant pressure it'll slowly go back down.

I'm not sure what jamesmartin was trying to say - I appreciate the pedal will be harder when the servo isn't helping, but I don't understand why there appears to be a loss of pressure with the engine running, but not when it's stopped.
 
If the pedal stays put with the engine off, but slowly sinks with the engine running, would have said servo myself Ian

Let's see what others have to say
 
Have you tried adjusting the rear drums? I know it does not sound like it, but un-adjusted drums can cause some werid symptoms!
 
servo cant make pedal spongy,it can only push against mastercylinder rod system would have to have air or cotamination too much free play ,ballooning flexis
 
That's cool - I get that.

I bled the system fully this afternoon - new fluid all the way through to each brake. The car was bone dry underneath so I was able to check all the pipes and hoses - no sign of any leaks.

It still seems more like a master cylinder failure than anything else.
 
Back
Top