9 replies to this topic

[njathind]

Hi guys, I have a bit of a dilema with the brakes on my mini. The car is a 1997 MPI cooper with standard brake setup.

 

I have slowly been rebuilding the car over the past 4 years, about 6 months ago I replaced all of the calipers, wheel cylinders and the rear copper brake pipes. I bled the brakes using a one man kit and all was well, I had a good feel to the brake pedal and could use them to stop the car when rolling it in and around the garage. Now the other day I went to start the car up and take it for a quick spin on the drive, I tested the brakes and to my horror the pedal went to the floor rather easily and there was no braking at all. I looked in the master cylinder resevour and found that there was little to no fluid left, the car has been kept in the same space in the garage over the past few years and there have been no leaks or pools of fluid under the car, not even engine oil! So I am certain that there is not an external leak in the brake system.

 

So today I filled the master cylinder and bled all of the brakes, I was rather lucky as most of the air all came out in one go despite getting through several litres of brake fluid. So I took the car up and down the drive again and the brakes worked well, my only concern I have is the pedal will only travel about two inches and is fairly firm. Now I know the car has brand new pads and shoes on so they will need bedding in, the braking power is okay and if I slam the pedal as hard as I can at about 15-20MPH I get a chirp where the wheels are locking up.

 

It just does not feel natural to me, I am also rather concerned as to where the brake fluid went? It has not leaked externally so why was the resevour empty?
Is this how the brakes should feel on a mini? I dont want to spend my time bleeding brakes and adjusting rear shoes when this is how the brakes should feel.

 

Another peculiarity is if I were to pump the brakes in my MG with the engine off, the pedal will slowy get harder and harder untill I start the engine and the pedal returns to normal. If I do this in the mini I dont get a build up of pressure, however if I depress the brake pedal slightly and then start the car I feel the brake pedal dip slightly as I believe all servo assisted brakes should. Again is this normal behaviour from a mini braking system or not?

 

If its of any help the master cylinder has a green band on it.

 

Many thanks Nat

[KernowCooper]

If you had no air in the system and the fluid dropped its possible the rear seal on the master cylinder leaked it into the servo? if you've bleed it again and theres no loss of fluid at present, you need to slip the cylinder off the servo and see if its wet at the rear you cant be to careful.

 

You wont get a lot of pedal travel on the Mini if the brakes are all adjusted up on the rears, and sounds like you have good stopping power.

 

Slip the master cylinder off and investigate the rear seal area for signs of fluid

[njathind]

If you had no air in the system and the fluid dropped its possible the rear seal on the master cylinder leaked it into the servo? if you've bleed it again and theres no loss of fluid at present, you need to slip the cylinder off the servo and see if its wet at the rear you cant be to careful.
 
You wont get a lot of pedal travel on the Mini if the brakes are all adjusted up on the rears, and sounds like you have good stopping power.
 
Slip the master cylinder off and investigate the rear seal area for signs of fluid

When I bled the brakes a second time I did get a bit of air from all four wheels but no where near as much from when I was bleeding the system first time around. I will investigate the master cylinder, if the master cylinder is leaking into the servo could this be the cause of no pressure building up when the engine is off? Or is this normal behaviour for a mini?

If I remove the master cylinder without draining the system should I get fluid leaking out normally or only if the seal is faulty?
Also the rear drums are adjusted up as much as possible without causing the rear drums to bind, I guess this is normal?

[Yoda]

when you split the master cylinder from the servo, everything should be nice and dry in there. If there is any brake fluid on the back of the M/C then you have a leak and the servo will need to be cleaned as well as new seals in the M/C.

[KernowCooper]

Beat me to the obviously correct reply, 1 up to you this time

[njathind]

Many thanks guys, will go out and investigate to see what's what.

[njathind]

when you split the master cylinder from the servo, everything should be nice and dry in there. If there is any brake fluid on the back of the M/C then you have a leak and the servo will need to be cleaned as well as new seals in the M/C.

 

Well I split the master cylinder from the servo today, it was bone dry inside. Not a trace of brake fluid at all, should I assume everything is ok and there is not a problem with the brake system?

 

Slightly stumped now

[Yoda]

dunno where the brake fluid went then? but if all feels good on the pedal and the fluid is no longer dropping, then it should be good to go. Yes when you start the engine with your foot on the pedal you should feel a slight dip, so that all tends to suggest the servo system is working fine!

 

 

Maybe the brake fluid was stolen by the brake fluid faeries?

[njathind]

dunno where the brake fluid went then? but if all feels good on the pedal and the fluid is no longer dropping, then it should be good to go. Yes when you start the engine with your foot on the pedal you should feel a slight dip, so that all tends to suggest the servo system is working fine!

 

 

Maybe the brake fluid was stolen by the brake fluid faeries?

 

Ha Haa, I like your logic. Who knows, I'll just have to be careful when out on the road.
 

Many thanks for all of your help, Nat.

[Yoda]

My logic is founded by the force, unlike Dr Spock who seems to think logic is logic and everything is made up of Logic.

 

If explain it you cannot! 

 

Make something up!

 

 

LOL.

 

Take care!