Still got brake problems!

[Geoff Butcher]

As I recounted earlier under 'Wheel cylinder' I had no end of trouble bleeding my brakes and eventually had to let my man have a go at it. After that it was OK, the pedal biting higher up than it had ever done. However since then the pedal has been getting lower and lower. It still feels firm when it does bite, and it won't pump up as you'd expect if there was air in there. It's had an MoT and there were no signs of a leak, but the pedal is heading inexorably towards the carpet. I just don't understand what's going on, so if anyone has a bright idea please let me know...

[Rich]

What have you replaced so far Geoff?

[Hans Efde]

I think you already replaced the servo? That was in my car the culprit. I removed it completely and put the master cylinder straight on the brake pedal.
Another issue is the play between the rod coming out of the servo and going into the master cylinder. We solved Ed's similar brake problem by putting a small cap on the rod. You can do that by unbolting the 2 bolts of the master cylinder and carefully lift it. There should be enough slack/play in your brake lines.
Ed had 2 thicknesses, the thickest one caused already braking at standstill! So he put the thinner cap on and since then dead stroke is gone and the brakes bite quickly. Worth a try, quick and easy.
Good luck, Hans

[Geoff Butcher]

What have you replaced so far Geoff?

Rear wheel cylinder, one caliper due to broken bleed screw, and m/c, not that there appeared to be anything wrong with the previous one when I took it apart. It was only a couple of years old anyway, same as the servo.

[Rich]

I've had issues with the brakes, initially the long travel which I 'cured' with a cap on the rod in the servo, unfortunately even on the thinnest the brakes would bind on after about 10 miles. I ended up spacing out the alloy pedal pads to reasonable effect.

More recently I've had the ever diminishing bite point which reached it's natural conclusion over winter with a complete failure of the master cylinder. No leaks or anything like that, and the seals appeared good when I took it apart. After rebuilding with a Bigg Red kit I had a pedal again but was having to pump the brakes, it turned out one of the hub nuts had slackened off and the resulting (imperceptible) wobble was knocking the pads back. I only found this when it loosened enough to cause driveline noise.

Next plan is to build a twin cylinder set up that will allow me to dial out and slack without binding the brakes..

[Geoff Butcher]

Well, I'm pretty sure I haven't got wobbly hubs, and I dare say a spacer on the pushrod is a good idea but it won't stop the pedal gradually subsiding.I've just checked the fluid and it hasn't lost any. Even if it had been leaking I don't see why it would affect the bite point until the reservoir was empty and it gulped some air in. If it has got air in how did it get there? It can't get into the m/c with a full reservoir, and if air is getting in surely fluid must have come out? Next idea please!

[Hans Efde]

I think that could be a servo problem. I had something similar on my car. Everything okay, no leaks, but a very soft pedal. Another possibility is brake fluid leaking into the servo. When you lift the master cylinder, shine into the servo with a torch light and see if it's wet.

[Geoff Butcher]

It's a brand new m/c, and the old one wasn't leaking when I took it off. The fluid has to get past two seals to get into the servo and it doesn't seem to have lost any fluid since it was bled. I don't really see how the servo itself could be causing my problem, as it's not actually part of the hydraulic system.
Subsidiary question: how does the so-called 'pressure reducing valve' which is screwed into the m/c work? I assume it's really a pressure limiter?

[Geoff Butcher]

I've been wondering whether I could fit twin master cylinders with the cylinders vertical

[mikeeskriett]

Hi,

I had similar fun with my Gold a while back I ended up using an easy bleed and an inordinate amount of fluid I was having fun with air by the master cylinder and found that because the brake pedal has less travel at the bottom of the stroke than a metro it wasn't getting the last bit of air out. The ezi bleed sorted that out. the other thing i had was an issue with the taper washer/drive flange where due to wear and despit being tight there was some movement which allowed it to knock the pads back so you had to pump the brakes up to stop. Luckily the local spares shop had both a nut and taper washer in stock which was surprising, I've since changed the drive flange.

Cheers,

Mike