Master cylinder part 2

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

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

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.

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

The message from "mrcheerful ." contains these words:

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

You sarcastic bugger. :-) Mike.

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.