Brake master cylinder

[naasaa]

Does anyone have any thought or experience with aftermarket brake master cylinder?

Like the one from SJS?

Mine is shot beyond repair.

 

Lars

[Andyww]

I have just decided to replace mine. 

I seem to be having a massive problem with bleeding the brakes, I have tried the conventional method, a pressure bleeder and vacuum bleeder. I have come to the conclusion that the master cylinder is not returning properly although I have just replaced the seals. I just cant get the pedal solid.

I received one from SJ this morning and it looks fine. Although I am pretty sure its the same as the Ford Capri which are available on Ebay for much less I decided to order it from SJ for more comeback if it gives problems and also I can phone Steve for advice if I still cant get the damn thing to bleed.

In fact the only other issue must be the servo if I still cant get it working.

When I replace it I am going to bench bleed it first which might help. 

[naasaa]

OK.

I just replaced the seal yesterday at mine, and have the same problem as you.

so please let me know how this will work for you.

 

Lars

[jonroberts]

The old Girling master cylinders are no longer available as far as I'm aware, but the originals can pretty much always be saved by re-sleeving them with a stainless steel inner - its a specialist job but not too expensive. The most common issue is pitting and corrosion from infrequent fluid changes that tears up the seals.

When refitting new seals I now always use a smear of 'red rubber' grease on them and the cylinder inside prior to reassembly. The grease is a much better lubricant than thin brake fluid and I did experience the same issue as you. The rear piston has a softer spring on it compared to the front circuit one, so this is the one that 'sticks' first leading to it not returning far enough to uncover the inlet hole.  My tip is not to press the brake pedal at all during the bleeding procedure and use only a pressure bleeding system (Gunson EzBleed or similar). Once all the air is out the pistons don't move very much at all compared to pedal bleeding where they are moving over much more of their length than in normal operation. Only once all the air is out, and it can take quite a while, lock down the bleed screws and try the pedal.  If still soft, repeat pressure bleeding.  @Andyww is spot on that you should bench bleed the master cylinder to get it primed and most of the air out before fitting.  Bench bleed far, far away from any car bodywork - stray spurts travel a long way!

Grade of brake fluid can also have an effect. Many years ago I filled with Automec synthetic DOT4 fluid and it was a pig to bleed, plus leaks appeared at the handbrake lever on the rear callipers. Stripped and rebuilt everything again and use DOT3 now. 

[naasaa]

The problem with my cylinder is corrosion. Particular in the rear circuit.

I do use paste when installing the seals. In fact, grease, paste or silicone is to be used for all kind of seals during assembling.

I bench bleed master cylinders by means went screws and tubes. Hence I can avoid the mess by draining into a container.

I must say that I always use DOT 4. Not that it is necessarily better that DOT 3, and even requires a more frequent change. But just to avoid mixing it up in different cars.

Will look into having the cylinder sleeved. Though my concern is that I find the sleeve kind of long compared to the Ø.

[Andyww]

Thanks Jon, your description matches exactly what I found. the first problem I had was the front circuit would not fill up at all, and that must have been the front piston not retracting past the hole. I think my first mistake was bleeding the rears first, as that might have caused the rear piston to be permanently pushing the front piston forwards.

The problem with the pressure bleeder (Sealey with a manual pump) was the pedal would be OK until the bleeder was de-pressurised and then there was a bubbling of fluid being sucked up into the reservoir, then the pedal would be spongy. Manual bleeding did seem to work better. But I will try again with the new master pre-bled and with the pressure bleeder.

Not sure about the DOT 4 thing though. I am using DOT 4 and would try to do so owing to the higher boiling point. I have not heard of DOT 4 causing any problems with seals etc. The problems in this area seem to be from DOT 5 silicone fluid. I thought the Automec was DOT 5. In fact I am not sure why DOT 5 is even produced as everyone seems to warn not to use it. Another problem seems to be its desirable property of not absorbing moisture has an undesirable result of allowing moisture to remain in the system for ever. 

[jonroberts]

I made a mistake on my previous post - the synthetic fluid I used and didn't like was Automec DOT5 silicone fluid not DOT4.

[naasaa]

DOT 3, 4 & 5.1 are glycol-ester based brake fluids. But all hygroscopic, hence they have to be flushed depending on surrounding climate.

Used to live in Florida, very humid,  which did require the brake fluid being refreshed more often than here in Denmark. However, DOT 3 can contain more water than DOT 4, so it have to be refreshed more often than DOT 3. DOT 5.1 have an even higher boiling point than 3 & 4, but require also even more often to be refreshed.

DOT 5 is based on silicone and can not contain water, and is not as wear resistant as the glycol-ester products. But will not harm any painting.

[Andyww]

I fitted the replacement master cylinder from SJ and all is good.

This is what I did which worked without any hassle:

I bought 2 bleed nipples which fitted the outlets of the master cylinder. Had to wrap teflon tape around the threads as they were not a very good fit.

Bled with the cylinder in a vice, alternating between the front and rear, getting all the air out took quite a while. Closed on up stroke each time.

Fitted to the car. I noticed the plunger from the servo was contacting the piston before the cylinder was fully seated on the servo so I backed off the nut and shortened the pedal linkage slightly.

With the cylinder fitted and still the bleed nipples fitted, checked the pedal which was solid.

Connected front pipe and left bleed nipple on rear outlet, closed. Used the Sealey pressure bleeder with the gauge only showing a very small pressure, less than 10 PSI and bled both fronts.

Pedal was now solid but bashed it a few times to dislodge any more air and then bled fronts again.

Connected rear and repeated above with rears.

[naasaa]

Hi Andy

Good to hear. I will then place an order for new master cylinder.

Did you notice which brand it is?

Lars

[Andyww]

Its just a generic one, no brand. The spec is 20mm bore and I am pretty certain its the same as Ford Capri. It looks like the Capri used either Girling or Delphi brakes originally and its the Girling equivalent version. 

[C43]

FYI the brakes on my brothers S2 were shot. I wanted to use the standard master cylinder so I got it re sleeved (it had heavy corrosion along the bottom of the bore where the car had stood which would not polish out). I pressure bled the brakes, drove the car for a few miles and then pressure bled again and brakes good thereafter. The comment when the car was in for MoT were brakes better than an Elise which I was pretty chuffed with.

C43 

[naasaa]

Just ordered a new master cylinder, overhaul kit for the rear caliper and new hoses for the rear.

Just to be sure that I can enjoy the front Wilwood kit.