Brakes seizing

Post by **badfelafel** » Tue Nov 27, 2007 4:00 pm

Hi all

Not been around for a while and been missing the forum!

You might remember I posted about my brakes seizing after a few applications. But now I'm a bit puzzled, as they seem to seize even if I havent been using them...

At the start of a journey (eg if the car hasnt been used for more than an hour) the brakes are fine. But over a couple of miles they stick and eventually bind so strongly the car cant be moved.

I've tried driving without using the brakes at all, and they still come on and bind (we had tied the problem down to retaining pressure - its a disc brake conversion).

Could it be due to clutch use? Or something else?

Cheers all

Barry

Post by **Orkney** » Tue Nov 27, 2007 4:14 pm

I've tried driving without using the brakes at all, and they still come on and bind

what you mean they come on on thier own even if you dont touch the pedal?

If its not the valve in the MC or somesuch when you drive and they stick worse but free up after a while that might point to the insides of the cylinders that push the pads being corroded - have you had them apart and had a look?

Cant see how the clutch could have anything to do with it at all.

Sounds blooming dangerous, soetimes being able to go is just as important as being able to stop

Post by **Axolotl** » Tue Nov 27, 2007 4:31 pm

I'm guessing there's a servo added to your braking system when the disk brake conversion was done?

In that case, I think your problem is that the servo is leaking air into the "air pressure" side of the diaphram that provides brake assist as though you are pressing the brake slightly all the time. In effect, your brakes are leaking "on". They'll reset themselves after the car has stood for a bit as the servo naturally loses vacuum on the vacuum side of the diaphram, and both sides return to atmospheric pressure.

This could be because:

a) Something is pressing the brake slightly all the time, e.g. if there is no slack between the brake pedal movement and the master cylinder actuating rod.

b) The valve in the servo that is supposed to cut off atmospheric pressure when your foot isn't on the brake is leaking or stuck open.

c) The servo casing has an air leak, perhaps due to corrosion, accidental damage or poor assembly.

I'd check the adjustment on the master cylinder actuating rod, and if that is as it should be, get the servo checked out by an expert. I don't know if the servos are servicable items, but it may be cheaper and easier just to replace the whole thing, depending on how old the system is.

Post by **badfelafel** » Tue Nov 27, 2007 4:38 pm

No servo ...

Post by **badfelafel** » Tue Nov 27, 2007 5:02 pm

incidentally - they seize very gradually - its not sudden

Post by **flying** » Tue Nov 27, 2007 5:12 pm

my sister had this exact problem after i got it on the road...took a while to work out what was causing the problem was.....it turned out to be the rod that goes in to the brake master cylinder was out to far so it was already putting the brakes under pressure...and when the brakes are adjusted to that it sticks after it gets warm....back the pin off and re adjust the brakes and that should sort it

Post by **Axolotl** » Tue Nov 27, 2007 5:15 pm

No servo eh? Oh well, it was a good theory while it lasted.

Can you tell which brakes are binding?

Is it all four, or just the disks, or just the rears?

And do they just reset themselves if you leave it, or do you have to do something to make it driveable again?

Post by **badfelafel** » Tue Nov 27, 2007 5:21 pm

Thanks for info

I think its just the fronts that bind
They free themseloves if the car is left for an hour or so

It has been an expensive mystery so far!

Post by **Axolotl** » Tue Nov 27, 2007 5:32 pm

the rod that goes in to the brake master cylinder was out to far so it was already putting the brakes under pressure...

Like a) in my first post. Don't see how that puts the brakes on more and more as you go though, without a servo to asssist them "on".

Do they lock on as they heat up with the slight pressure?

Post by **flying** » Tue Nov 27, 2007 5:38 pm

Axolotl wrote:
the rod that goes in to the brake master cylinder was out to far so it was already putting the brakes under pressure...
Like a) in my first post. Don't see how that puts the brakes on more and more as you go though, without a servo to asssist them "on".

Do they lock on as they heat up with the slight pressure?

yes they do until you take the whole hub off and put it back on again then it would so it again...once i adjusted the rod it didnt happen again

Post by **steve4063** » Tue Nov 27, 2007 8:22 pm

the pin which joins the clutch and brake pedal may be stiff slightly siezed and thats why it may be doing it slitghly if you catch my drift.

so as you put the clutch down its slightly moving the brake pedal as well they are known for seized pins.

plenty of plus gas then spray grease on the pin that joins them as well

i'm wondering if it is the m/c push rod adjusted wrong and instead of aloowing the fluid and pressure to decrease its not backing off enougfh and forcing the brakes more and more on.

the pedal should move 1/2 inch before you feel it hit the piston in the m/c if not loosen it up so it does.

good luck and keep us informed

Post by **badfelafel** » Tue Nov 27, 2007 9:47 pm

Great

Thanks!

Will let you know

The best kind of suggestion is one that doesnt involve lots of money!!

Post by **rayofleamington** » Tue Nov 27, 2007 10:31 pm

just to ask the obvious first...

1)do the caliper pistons move freely? If they are stiff do they move when the bleed nipple is open?
2) with the pistons back is there enough (lots of) clearance between the pads and the disk? I once had a new set where the disk or pads were too thick and were binding a little until I shaved the pads!
3) have you removed the one way valve in the end of the master cylinder bore? This valve (if it works really well) is not compatible with disk brakes.

Post by **bmcecosse** » Wed Dec 05, 2007 11:18 pm

Barry - been on hols so missed your thread till now - I'm going with Steve on this (and your own original suggestion) - the brake may well be being dragged on by the clutch pedal - so apply lots of plus gas etc. Interested to know how you drive the car in Glasgow without using the brakes!! But if you really don't use them - and the brakes still come on - then it really HAS to be interaction between the pedals.

Post by **badfelafel** » Thu Dec 06, 2007 12:28 am

It's beginning to fit together... I remember before the problem started that if you used the clutch and brake, then released the clutch, the brake pedal wouldnt immediately return. It had been doing that for ages...

So it looks like it all makes sense. Guess theres some lubrication needed along that bar the pedals run off.

Question... whats the best thing to use? Will plus gas be lasting? Should I be greasing it or using something else?????

Thanks for all suggestions!

PS Hope you had nice hols, bmc --- still got parts waiting for u if you want them!

Post by **Orkney** » Thu Dec 06, 2007 7:00 am

nice to see you back BMC - thought youd abandoned the place during the tec problems - we just need Big Ging back now!

Lubrication - almost an art form.
Penetrant 1st, a specialist one is best, wd40 or such at a push. Get loads in and move lthe joints like crazy and watch all the brown gunk come out.
Then you need to oil it - wd wont stay there for long - a proper oil and 3 in one is good is a nice thinnish oil that will work itself in nicely.
best one if your stripping something like that is copper grease - they even do a spray but its a bit on the thin side although great on protection brake parts.

Post by **bigginger** » Thu Dec 06, 2007 1:01 pm

He's lurking...

Post by **jonathon** » Thu Dec 06, 2007 1:21 pm

Hello Lurker !!

Post by **bmcecosse** » Thu Dec 06, 2007 1:34 pm

Thanks Barry - yes that's all making sense now!!!! Give a good blast with plus gas etc and wiggle the pedals about until they seem free - then add some oil - EP90 may be best but engine oil should be ok too. Pity we didn't come up with this idea about 6 months ago - but you never mentioned the pedals were binding together!! And yes - need these parts asap - let me know when would be suitable and I will come and collect!!