6 replies to this topic

[maddogmcg]

I know this insn't exactly a mini question ,but as half of the car is mini then im asking it anyway

I am having problems bleeding the brakes on my special . On the rear are mini rear back brakes ,on the front are triumph herald drum brakes ,the master cylinder is also ( i believe ) from a triumph herald . The master cylinder is an old ally cast girling type with a single outlet .I have replaced the seals in both the master and front slave brake cylinders .

Using pressure bleeder didnt work as the fluid just dribbled out with no pressure behind it .

We then tried the assistant pressing the pedal method and found that with the first push of the pedal produced no pressure ( the pedal hits the floor ) watching the fluid level in the master cylinder it was noticed that it dropped quite a lot .

The second press of the pedal produced a good flow of waste fluid from the opened nipple ,after holding pedal down and closing the nipple ,the pedal was released and fluid was seen to flow back into the master cylinder reservoir .

Obviously this isnt a safe way to drive ,does anyone have any advice , should fluid flow back into the master cylinder ? Would a seal fitted the wrong way around inside the master cylinder cause this problem ?

[998dave]

Have you adjusted the drums brakes? They're not self adjusting on a mini. (and possibly not on the triumph either).

Slacken off handbrake, and adjust the brakes til the wheels are locked, then back off just enough to turn them. Now bleed rear's then fronts, readjust handbrake.

I also presume you have a clear pipe of the bleed nipple with the other end submerged in a jar of brake fluid, so that any air pushed from the system isn't pulled back in?

Fluid should flow back into the master cylinder, but not into the master cylinder resevoir, I'm not familiar with the Triumph set up, so can't comment, but if you showed us an image I might be able to have a guess...

Dave

[maddogmcg]

cheers 998dave

yes i have adjusted all brakes the triumph front are manual adjust also ,i have used a tube connected to the nipple etc .

i have wondered if the early mini had some sort of brake compensator valve ,i think the system is similar to the single line system fitted to early minis and once had a lot of trouble bleeding the brakes on a 76 mini with the brake inertia valve fitted to the bulkhead ,did early minis have a similar valve on the system ?
Its quite difficult to trace the brake pipes as they are inside the car behind panels ,the car is a one off built in 1971 ish details are sketchy .

I will check the brake adjustment again and start at the master cylinder bleeding the system at every joint , i have done this with the pressure bleed device before as it works without the bleed tube to prevent air getting sucked back in the system .

i dont have a pic of the master cylinder ,but it is an old girling 3/4 cylinder as used on triumphs /fords /vauxhalls and a lot of 60's 70's cars .

Attached Files

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[dklawson]

That's definitely a Triumph front suspension. Out of curiosity, did you build this yourself and if so, why use the TR front drums as opposed to the disk setup off a Spitfire or GT6? Both those cars kept a single line brake system through the late 1960s with disks up front and drums in the rear. I don't remember if there is a proportioning valve on the TRs but their certainly was on the early Minis to keep the back brakes from locking prematurely.

When you manually adjust the drums, remember that properly adjusted means that you will hear the shoes scrub the inside of the drums when an elevated wheel is rotated by hand. The wheel should also stop spinning within about a revolution when you stop spinning it. Anything looser will result in excessive pedal travel and/or the need to pump the brakes to get the car to stop.

You said you had fluid going back into the master cylinder reservoir. How do you know this and where did you observe this? Lastly, since you may have built this yourself, did you make sure the bleed nipples on the wheel cylinders were at the top as installed? If the nipples are coming out the bottom you'll never get all the air out.

[maddogmcg]

no i didnt build it myself as i was only 5 at the time lol
the brakes are as came with the car and i am told when they are working there is no need for disks on the front as the car weighs very little ,its alloy and wood panels .

my bleeding assistant noticed it as he was pressing the pedal ,the cylinders are under the bonnet bulge and the level can clearly be seen to rise after the final pump/ tighten nipple , when the pedal is released .

yes bleed nipples are at the top .

was talking to a friend who ran series one landrovers ( they are fitted with a similar master cylinder ) and he said you have to literally stamp on the pedal a few times then release the nipple to bleed them properly .

thanks for your reply

i will get my old mini haynes out and look for the proprtioning valve

[dklawson]

If you find that this car has a proportioning valve, your second bleed method of stamping on the pedal and then loosening the nipple... it will not work.

The early Mini proportioning valve is really a type of pressure limiting valve. When pressure reaches a certain point in the rear brake lines, the valve "closes" to prevent further pressure from locking up the rear drums. The pump-up, then crack the nipple bleed method is particularly ineffective when that valve is present. The pumping closes off the valve so when you crack the nipple you get one quick, tiny pop of fluid and that's all.

If the shoes are properly adjusted and there is no air in the system, only the smallest amount of fluid should return to the master cylinder when the pedal is released.

[maddogmcg]

tried again to bleed the brakes i adjusted the brakes till they all locked and found giving them a good repeated stomping on then cracking nipple did the trick

obviously then readjusted them and topped up the fluid !

thanks for all the replies