Binding brakes

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KevW
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Binding brakes

Post by KevW »

I took the car for a 20 mile run today and towards the end the brake pedal began to feel a little wooden. I parked up at home for 30 minutes then drove off again. The first time I applied the brakes they bound on.
I managed to get the car back onto my drive, raised each wheel on the jack and found they were all bound fast.

I reckon this rules out a sticky calliper piston and points towards a collapsed brake flexi pipe.

Does anyone know the best place to get a replacement flexi. Is it a case of calling on SJ Sportscars or are Toyota dealers a better option?
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Steve C
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Post by Steve C »

If they're all bound on, I would guess it's more likely to be the master cylinder sticking, or the pushrod adjustment to the servo doesn't have the correct free play.

If you open a bleed nipple on one caliper and all release, it pretty much confirms that it's the MC or servo / pushrod adjustment.

Good luck!

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Post by KevW »

Thanks for the suggestion Steve. I'd just thought it may the flexis acting like a non-return valve because when the brakes had been left to cool for an hour they were OK.
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Danny
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binding brakes

Post by Danny »

I had a Peugeot many moons ago that had the same symptom, it turned out to be the flexi hose had perished internally and was acting as a one way valve so I would not rule that out as a possility.

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master cylinder

Post by AndyC »

If one stuck on then I'd agree flexi pipe could e the cause, but if it's more than one wheel then you need a cause that's common to those wheels, so master cylinder area is a likely cause, unless you're unlucky and have all 4 flexis fail simultaniously.

I guess nobody's fitted a non-return or limited return valve in the system.

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Post by KevW »

Brakes still playing up.

Took the car for a 20 mile run - everything OK. Parked up for 1 hour and all four brakes had locked themselves on without me even touching the pedal. An hour and a half later the brakes had freed off again.

I reckon the servo must be at fault so that's the route I'm now going down.

TBC...
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mds666
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Post by mds666 »

after the 20milr run, were the wheels hot?

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Steve C
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Post by Steve C »

Before changing anything expensive .. try shortening the pushrod from the brake pedal to the back of the servo a little (there's a locknut and it then screws in / out). If it has been set with no free play at all, that could be the cause of the problem. As the fluid expands a little, if the MC can no longer return to rest & vent correctly to the resevior, it could pressurise the whole circuit.

In conjunction with this, it could be the brake fluid boiling because it's old, try changing that too (if you haven't already).

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Post by KevW »

The wheels seem normal temperature after a run.

Thanks for that tip Steve, I'll take a look.

Another possible cause is maybe that the seals in the master cylinder are swelling up and restricting the return flow to the reservoir when I release the pedal. When everything cools down the seals contract and the brakes unstick themselves.

I don't yet know if seals are available
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Post by dpr59 »

KevW wrote:
Another possible cause is maybe that the seals in the master cylinder are swelling up and restricting the return flow to the reservoir when I release the pedal. .
A rubber swell test is one done on brake fluid and this would most likely be a non reversable characterisitic of the material.

Also, if the fluid had a lot of water absorbed, which boiled during braking then this would release as the temperature dropped again and the water returned to it's liquid phase.

Sounds a more mechanical issue to me, sorry I can't help more as I've not experienced this.
A

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Post by KevW »

After driving about 300 miles in the past four days I can't get the binding symptoms to occur again. I even went from Newcastle over the moors to Stanhope yesterday, which is a really twisty, hilly route, and the brakes behaved themselves.

I've decided it's pointless to replace any parts until if/when they give any more trouble.
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Post by amarshall »

KevW wrote:After driving about 300 miles in the past four days I can't get the binding symptoms to occur again. I even went from Newcastle over the moors to Stanhope yesterday, which is a really twisty, hilly route, and the brakes behaved themselves.

I've decided it's pointless to replace any parts until if/when they give any more trouble.
She was just lonely and seeking attention. After spending the day in the company of other Lotuses, she's happy... for now....
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KevW
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Post by KevW »

It's the "for now" that worries me...
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Post by robertverhey »

No-one's mentioned the parking brake yet. I had a Renault 12 once that used to lock its brakes on because the shoes had been soaked in fluid from a leaky wheel cylinder. The mechanic called it "brake wrap", the wet shoe forms a very tight seal with the drum. enough to stop you in your tracks....very very scary!

Unlikely to be this due to 4 wheel disc nature of excel brakes and physical separation of the parking brake mechanism.....but I'd be whipping off those rear discs and having a look.

Robert
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Re: Binding brakes

Post by micha »

i would check the brake-servo of malfunction. had the same thing on an elite.

the rod from the pedal to the servo normally does not change its "length" (until you do not find a loose locknut there.). you can shorten that, but mark the orignal position.

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