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Master cylinder part 2

Bugger. I knew it was too good to be true, what with my luck an' all.

I replaced my master cylinder t'other day and all was fine. Today, after driving a mile or so, I noticed that the brake pedal got firmer to the touch than usual and only required half a toe on it to stop the car.

There was the unmistakeable pong of hot brakes so when I stopped for petrol I had a quick feel of the wheels and the offside was very hot, indicating a binding brake.

Whyzat then??

I'll whip the pads out tomorrow and see if the piston's stuck out but I don't see why it should start right now. The old master cylinder had been a bit lacking (slightly leaking seals on low-pressure applications) for a good couple of months if that makes a difference.

Si

Reply to
Mungo "two sheds" Toadfoot
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May be the same thing I managed to do the other day. I adjusted the brake light switch too far down which held the brake very slightly on. Must be worth a check before taking anything to bits.

mrcheerful

Reply to
mrcheerful

That's something that I would never have thought of and when I first read it I did dismiss it, but now having thought about it...

The old, not working properly, master cylinder allowed the pads to rattle in their calipers and the pedal travelled further than it should have. Not dangerously so because except for very light applications the brakes worked as well as they ever did. But now the MC is holding the pads to the disc as it's supposed to, the pedal is much firmer and braking starts "earlier". Investigations will be carried out in the morning.

Ta :o)

Si

Reply to
Mungo "two sheds" Toadfoot

Sounds like the brake pedal clearance to master cyl needs adjusting. Especially likely as you say the pedal gets firmer.

With the footbrake in it's at rest position, there should be clearance between the m/c actuating rod and the m/c piston. If the m/c piston can't return far enough, brake fluid can't return to the master cyl reservoir, and is held in the brake system. As the brakes warm up the fluid expands and as it can't escape into the reservoir, it puts the brakes on. An easy way to check if that is actually the problem is while they're still binding, slacken off a bleed nipple. If the fluid comes out under pressure, and the wheels freely rotate. 10 to1 the problem is with the m/c clearance. Mike.

Reply to
Mike G

You can also make that check without slackening bleed nipples by slackening the master cylinder securing nuts, if that allows the wheel tp turn freely then you know you have a problem with the pedal/link/etc. rather than hydraulics.

mrcheerful

Reply to
mrcheerful

The message from "mrcheerful ." contains these words:

Cor - that's clever. I'd not have thought of that!

Reply to
Guy King

You sarcastic bugger. :-) Mike.

Reply to
Mike G

The message from "Mike G" contains these words:

No, I meant it! I really wouldn't have thought of just slackening off the mounting bolts. I'd have taken the whole bloody thing apart if it'd been mine.

Perhaps I'd have thought of it once hands-on.

Reply to
Guy King

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