Received advice for this problem last month, solved it, but am now
experiencing similar problem for entirely different reasons.

Rebuilt the dual circuit MC over the weekend, installed MC and bled
the brakes today with a Power Bleeder.

Something's wrong, the pedal is going almost halfway to the floor
before the braking action begins. Brakes did not behave this way
before I pulled off the MC, they began slowing/ stopping car after
pushing the pedal a few inches. There WAS a fluid leak from front of
MC however, that was main reason I decided to rebuild.

Is there any way to easily determine whether problem is with the
bleed, or with the MC? Pumping pedal makes no difference. There is no
longer a fluid leak out of MC front however.

I'm going to try another bleed tomorrow and see if that helps, but I'd sure like to track down the root of the problem.

Damian

'68 Amazon dual circuit brakes /Girling front discs, Wagner drums rear/ Lockheed booster

Same problem on my rojo two months ago. Ending on local brakes workshop:

1) A hose was collapsed on one front brake, replaced.

2) My lockhead servo was positionated with its air filter up. I was wrong, that position made a headache for bleeding (air bubbles remain). Checking with installation manual, reposition with filter on right and down and check valve on left and down. Also inclining the servo - now shaft is not at horizontal, but inclined up (if you want, please email me to send you a electronic copy of that old manual). Bleeding ok now, no more spongy brakes.

Happy volving




--
Joaquin (yogui the bear) / Rojo 121 / Lima, Peru

I am very interested to know where you got the rebuld kit for the dual circuit master cylinder. Was it just rubbers, or did it include metal piston parts as well? Cost?

When you tore it down, how did the bore look?

thanks

Today I was told I should prime the MC before installing (fill reservoir with fluid, operate pushrod and let fluid run out on in stroke, but put fingers in front of pipe holders on the back stroke so no air is sucked in) Didn't know I need to do that with the Power Bleeder, but I'll give it a shot.

Bore was not bad, though there was a bit of rust near the back. No scratches, no marks. When I dumped out the remainder of the fluid, tiny black particles (rubber?) came out also. I polished up the bore, looks like new.

I found 2 places who have that kit, CVI (Sweden) and Swedish Treasures (USA) I got mine from CVI, cost with shipping was around $65.

http://www.cvi-automotive.se/resdela/5_bromsar/1_amzonbrakes.htm

The kit I purchased was #273076, photo on above link shows exactly what you get.

last time I rebuilt an MC I was not to pleased with the result, the rebuilt only lasted a couple of years. I does help to bench bleed the MC. with luck that is all your problem is. are you power bleeding with suction or vac? Vac does not always work as well as one might hope.
--
Patrick, '68 220, '83 245, '92 Eurovan (work truck).

Patrick, with the Power Bleeder, I filled the container up with fluid, attached it to the MC, and pumped it up to around 10 PSI. Then I went around to each cylinder and unscrewed the bleeder screws, forcing fluid through the system. I was told that 15 PSI might be the number I should be striving for, but nothing higher than that.

Yeah, I've heard rebuilds don't always last, I'm really not sure why that is. Incorrect reassembly? Rubber seals not up to par??

I used rebuild kits on both my clutch master cylinders, and they have been working fine for years. Maybe I got lucky!

Damian

damian, the thing with brakes is they are such a pain. Sometimes if go around the car again bleeding in sequence you will find the problem (air). The other possibility is that you have only half the MC working (improper assembly) or blocked orrifice. And finally if your rear brakes are not properly adjusted they will cause this symptom. This is the easiest to check, apply the hand brake, now try the foot brake, if the slack goes out of the pedal, it is excessive brake shoe travel that is causing the problem.
--
Patrick, '68 220, '83 245, '92 Eurovan (work truck).

Tried the handbrake test last night, made no difference. When bleeding the system, I wonder if it makes any difference whether or not the handbrake is applied. Probably not...

Going to remove the MC now before it gets too hot outside, and bench bleed. Then I'll rebleed the entire system and report the results.

Hope I didn't screw up the MC, was 99.9% sure I reassembled that thing correctly.