12 replies to this topic

[1275 neil]

went out for a drive in the car came back as the brakes had seived on the n/s calliper after it cooled down it was ok to drive again but a few times round the block the same thing happened any ideas could it be the master cylinder i have put new callipers on and new braided hoses on both sides and have bled the system any pointer greatly recived thanxs

[cowboy]

normally wit siezed brakes is a stuck piston, but i've just had a problem with mine.

driving alog and my brake pedal is solid. brakes are stuck on. ive wound of the brakes and its still doing it. im wondering if the reducer on the bulkhead is siezing up or as you say there is a problem with the master cylinder.

[Zebedee]

normally wit siezed brakes is a stuck piston, but i've just had a problem with mine.

driving alog and my brake pedal is solid. brakes are stuck on. ive wound of the brakes and its still doing it. im wondering if the reducer on the bulkhead is siezing up or as you say there is a problem with the master cylinder.

I also have this problem but with both my rear brakes siezing on after a few miles.
Someone please help us.

[Turbo Nick]

common problem is for the flexi hoses to break down inside and stop the fluid moving back from the pistons.

[dklawson]

As stated above, start by replacing the flex-hose. Until you experience a collapsed hose you wouldn't believe how much they can trap pressure. When the hoses collapse they work just like a check valve and you can't even see the problem from the outside. (Don't go looking for a pinched sot on the hose because you won't find it. ) If that doesn't correct your problem, then move on to rebuilding the calipers (do both at the same time).

Zebedee, this applies to your rear wheel cylinders as well except it's often less expensive and quicker to replace a rear wheel cylinder than to rebuild it. However, start with the flex hoses.

[Zebedee]

Thank you DKlawson,

I am currently away at the moment but will try the hoses first.
I would never even have got to checking the hoses.

Thanks again.
Zeb.

[Ethel]

How likely is it for both hoses to fail though?

If it is the hose on a front caliper then I'd think you'd have no trouble pushing one piston in as it'd just push the other out. If both pistons move freely but not at the same time then I'd think hose.

[dklawson]

If it is the hose on a front caliper then I'd think you'd have no trouble pushing one piston in as it'd just push the other out. If both pistons move freely but not at the same time then I'd think hose.

Sorry, you lost me there. Can you elaborate a bit on what you're saying?

Depending on the age of the car it's quite possible for both hoses to go bad. Another possibility is that the proportioning valve is "stuck" and needs replacing. At one time there were rebuild kits for these but I don't know if they're still available.

[panelbeaterpeter]

This happened to me on a beetle, replaced the master cylinder and all was fine.

[Ethel]

DK,

The pistons in the same caliper are linked to one another so if the hose is blocked pushing one into the caliper will push the other out that would prove they aren't seized.

I accept both hoses can fail but can't be very likely for them both to go at pretty much the same time.

Regarding the sticking rear brakes It could also be down to the handbrake linkage or weak / failed pull off springs.

reversing the car would ease a spring related fault.

Wouldn't it be possible to isolate a hydraulic blockage strong enough to lock the wheels by selectively slackening a few ho connections or bleed nipples to see what's pressurised and what isn't?

[dklawson]

Thanks Ethel. I see your meaning now.

We have two different brake issues in this thread. The initial post by 1275neil was related to a single front brake. The second problem was posted by Zebedee regarding his car's rear brakes.

I see your point on the front caliper. If you don't have the disk in the way then you are correct that pushing one piston in will cause the other to come out if the flex line is blocked. If the disk is in the way, it will simply be difficult to push the first piston in at all if the flex line is collapsed.

With regard to opening a bleed nipple to test for a collapsed hose, you can indeed do that but you have to know what you're looking for. The first thought most people have is that they should see some brake fluid spray out as soon as they open the bleed nipple. Since brake fluid is almost incompressible don't look for that, not much fluid will come out if any. Instead you need to jack up the offending wheel (immediately after it locks up) and if it's a rear wheel release the parking brake. Spin the wheel and note how hard it is to turn (if it can be rotated at all.) Then release the bleed nipple about a half turn and then re-tighten it immediately. Check if the wheel is now easier to rotate. If it is, replace the flex hose. If it's not, look for problems elsewhere.

I agree that it is unlikely that both rear brake hoses would collapse at the same time. However, I think it would be equally unlikely to be both sets of return springs (or handbrake quadrants) failing at the same time. However, the proportioning valve is a single component affecting both rear wheels. If it sticks shut both rear wheels would be locked.

[Zebedee]

Hello again,

Thanks for all the suggestions, DKlawson, i think you are probably right about my proportional valve being the problem, i have had a new master cyclinder and brand new brake lines installed only 6 months ago so the weakest part in the system that i didnt change was the proportional valve.

Quick question:- if this failed would the rear brakes stay stuck on or as i seem to have, after driving back roads at speed for about 2 miles they gradually seize on?
after waiting for them to cool down i can then spin them freely. This has suddenly started happenning, i use the car to drive 30 motorway miles on a regular basis with no problems untill 2 weeks ago.

Unfortunatly i am 3500 miles away from home untill mid august so i cant actually check anything else on the car. But if it is a good diagnosis that the proportional vale may need replacing i can buy one befor i get home. Is it possible to fit an after market adjustable valve? as these are much cheaper and very easy to set up. My mini is dual line, late master cylinder type.

Any help is very well recieved.

Thanks again for the help so far.
Zebedee.http://www.theminiforum.co.uk/forums/style_images/1/folder_post_icons/icon9.gif
http://www.theminifo...icons/icon9.gif

[liam1288]

Thanks Ethel. I see your meaning now.

We have two different brake issues in this thread. The initial post by 1275neil was related to a single front brake. The second problem was posted by Zebedee regarding his car's rear brakes.

I see your point on the front caliper. If you don't have the disk in the way then you are correct that pushing one piston in will cause the other to come out if the flex line is blocked. If the disk is in the way, it will simply be difficult to push the first piston in at all if the flex line is collapsed.

With regard to opening a bleed nipple to test for a collapsed hose, you can indeed do that but you have to know what you're looking for. The first thought most people have is that they should see some brake fluid spray out as soon as they open the bleed nipple. Since brake fluid is almost incompressible don't look for that, not much fluid will come out if any. Instead you need to jack up the offending wheel (immediately after it locks up) and if it's a rear wheel release the parking brake. Spin the wheel and note how hard it is to turn (if it can be rotated at all.) Then release the bleed nipple about a half turn and then re-tighten it immediately. Check if the wheel is now easier to rotate. If it is, replace the flex hose. If it's not, look for problems elsewhere.

I agree that it is unlikely that both rear brake hoses would collapse at the same time. However, I think it would be equally unlikely to be both sets of return springs (or handbrake quadrants) failing at the same time. However, the proportioning valve is a single component affecting both rear wheels. If it sticks shut both rear wheels would be locked.

I'm having this problem with seizing up after a few miles, did what you said by releasing the pressure at the nipple immediately and the wheels did become easier to turn. I replaced the flexi hoses and still seizes on just at a slower rate.
It's only the fronts that cause the problem so does this mean my master cylinder isn't the problem?