12 replies to this topic

[muller295]

Hi everyone, 

As stated, my brake pedal (1992 SPI) does not return after driving for a while. When I get into the car the brake pedal returns just fine, with and without the engine running. The car does not have (the Dutch equivalent of) MOT, so test driving is not really an option. When I drove it to the MOT (15 minute drive) and they put it on the brake tester, the pedal would only return fully when you pull the pedal back manually. The brakes stay on if you don't pull it back.

 

So what can cause this? The master cylinder is brand new, so I don't think that should be it. What is so strange to me is, when you get in the car it's fine, but only when you drive it for a while, it will stick.

Thanks in advance!

Edited by muller295, 27 July 2019 - 11:22 AM.

[phillrulz]

Fluid level dropping ? 

[MiddletoM]

how new is the brake fluid? 

I have this problem in my 350z with the clutch and i know its old fluid. Only happens when the fluid gets hot.

[DeadSquare]

Hi everyone, 

As stated, my brake pedal (1992 SPI) does not return after driving for a while. When I get into the car the brake pedal returns just fine, with and without the engine running. The car does not have (the Dutch equivalent of) MOT, so test driving is not really an option. When I drove it to the MOT (15 minute drive) and they put it on the brake tester, the pedal would only return fully when you pull the pedal back manually. The brakes stay on if you don't pull it back.

 

So what can cause this? The master cylinder is brand new, so I don't think that should be it. What is so strange to me is, when you get in the car it's fine, but only when you drive it for a while, it will stick.

Thanks in advance!

 

"the brake pedal would only return fully when you pull the pedal back manually"

 

Has the return spring been properly refitted after the replacing of the master cylinder ?

 

 

If it has, so that you don't have to bend down each time, fix a bit of string to the pedal.

[muller295]

 

Hi everyone, 

As stated, my brake pedal (1992 SPI) does not return after driving for a while. When I get into the car the brake pedal returns just fine, with and without the engine running. The car does not have (the Dutch equivalent of) MOT, so test driving is not really an option. When I drove it to the MOT (15 minute drive) and they put it on the brake tester, the pedal would only return fully when you pull the pedal back manually. The brakes stay on if you don't pull it back.

 

So what can cause this? The master cylinder is brand new, so I don't think that should be it. What is so strange to me is, when you get in the car it's fine, but only when you drive it for a while, it will stick.

Thanks in advance!

 

"the brake pedal would only return fully when you pull the pedal back manually"

 

Has the return spring been properly refitted after the replacing of the master cylinder ?

 

 

If it has, so that you don't have to bend down each time, fix a bit of string to the pedal.

 

 

 

Although pragmatic, I don't think the guys at the MOT would appreciate that hahah. Do you even have something to do with a return spring when replacing the master cylinder?

 

Think I'll flush the brake fluid and see if it helps!

[DeadSquare]

 The guys at the Mot might not appreciate my idea, but careful reading of the the regulations may not prohibit string instead of a spring.

 

Getting the clevis pin out of the master cylinder is tricky for some people, and the spring may have been dislodged and not returned to the correct place.

 

Are the clutch and brake pedals in line ?  For the system to work, there must be full movement of the piston, because otherwise fluid can be pumped to the brake cylinders, but if there sometimes is not full movement, fluid is unable to return.  (See section M5 of the workshop manual)

[Ethel]

It'll be an issue with the servo.

[muller295]

Just tried to flush it for a bit, and it seems like there are some tiny bubbles (water?) in the fluid. Didn't have enough fluid for the whole system, so I'll try again tomorrow. I'll let you know if just flushing the system works.

[phillrulz]

It'll be an issue with the servo.

 

Thats what im thinking, once its been under vaccum from driving. 

[muller295]

Flushed the fluid, problem solved! Took it to the MOT, new problem is that the brakes at the rear barely work. Adjusted the drums already, so that is not it. I'm thinking there is a hydraulical problem. Anyone who can help me out?

[brivinci]

In between the front and rear is a proportioning valve to reduce the amount of pressure to the rears...so you remain facing in the correct direction when you go to stop:-) Clearly the fluid was old based on your previous question. It could have damage that valve, especially if a lot of moisture was in the fluid. When you flushed the system, do you remember getting perfectly fresh fluid out of the rear? Assuming this is a RHD car, you should have started with the left rear wheel cylinder. Another thing could be gummed up/stuck rear cylinders. Again, if a lot of moisture got in/around the cylinders the plungers could be rusted or stuck in place. 

[muller295]

Nearly everything in my brake system has been replaced by now. The car has been sitting for quite a while, as the last time it had MOT was in 2012. Brake fluid has been replaced since then, so the old fluid was not too bad. Bought a new limiter valve, so I will be fitting that this week. Fingers crossed it works out this time!

[Quinlan minor]

There is often a fundamental misunderstanding of how effective (reading wise) the rear brakes on a (classic) Mini should be.

Testers, used to seeing the figures for your average, porcine, rear disc equipped modern car, think the readings are too low. If you set a Mini up to give those kind of readings, given its light weight and short wheelbase, it'd lock the rears, every time, in the dry! In the wet, you'd be picking yourself out of the scenery every time you stamped on the pedal.