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Brake problem

Is it likely that a rear wheel cylinder which is slightly leaking could suck air into the braking system?

I replaced the master cylinder a while back and since then the brakes firm up as they get warmer until the front nearside smells really hot and the brake pedal becomes very firm. When the brakes have cooled down the pedal is fine again. I'm thinking this is because air's getting in somewhere and expanding when it gets hot. After bleeding all round it's fine for a few days and then it starts again. I noticed recently that one rear wheel cylinder is slightly leaking hence the question.

I'm also wondering if air could be getting in at the reservoir/master cylinder as it was a *lot* easier to put the reservoir onto the new master cyl. than it was to get it off the old one and there are sometimes tiny bits of pink rubbery stuff in the fluid . Is it usual to re-use the reservoir?

Si

Reply to
Mungo "two sheds" Toadfoot
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That sounds more like the master cylinder's got something wrong with it and isn't allowing fluid to return to the reservoir when not pressed. This may well be because it's already pushed down somewhat when it shouldn't be.

Reply to
Guy King

I would be pretty certain that the flexible brake hose has perished a bit and a bit of rubber sticks into the bore and acts like a one-way valve preventing the fluid from getting back when you release the pedal. If you loosen a union on the wheel side of the flexi-hose after applying the brakes and fluid comes out and the brakes come off, then that's your problem. I doubt if it's air, otherwise the brakes would get spongy, and I guess from your post that this is not the case.

Rob Graham

Reply to
Rob graham

That's what I wondered to begin with - perhaps I'd got a dodgy one...?

Any idea how/if I could test it?

Si

Reply to
Mungo "two sheds" Toadfoot

Thanks. I'm going to replace them all anyway when I change the wheel cylinders. I don't like doing bits and pieces over and over; I prefer to do the whole lot in one go if I can.

I'll give it a go next time it's seized up and it's not raining. I just printed off something from

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along those lines.

No, they definitely don't go spongy. Not in the slightest.

Si

Reply to
Mungo "two sheds" Toadfoot

As a quick test, you could try pushing back the piston in one of the front calipers as though you were going to change the pads. Only really conclusive if it won't move, but it's a start.

Cheers,

Colin.

Reply to
Colin Stamp

Good point - I remember trying that to see if they were seized and one side was very difficult to move. I thought it was just a lack of leverage at the time...

Time for some new pipes and stuff, I think.

Many thanks for the replies.

Si

Reply to
Mungo "two sheds" Toadfoot

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