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Master Cylinder problem?

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Does anyone ever bench bleed these MCs? I just put it all back together. Everything new in back, didn't touch the fronts other than look for leaks and bleed. Rebuilt MC too, but my pedal is still soft. Will bleed again but something ain't right, the brakes pull it down pretty good but pedal just feels soft. Maybe I'm just not used to a 60's era pedal anymore. I'm heading out to the store for long lengths of tube, I like the continuous circuit bleeding idea. I built a pressure bleeder from a garden sprayer but it always wants to leak and seems to somehow want to pump in air which is not good.
Lets say I brake test at 40mph, I should be able to lock it up without too much trouble, right? I can't, it stops pretty fast but not like it's supposed to I don't think, nothing to gauge it by, having only every driven one other Midget (my own 1500) that always had brake issues too....
 
Wrong, lots of luck on locken um up.
 
Mine locked pretty easily until I put the bigger tires on, now it seems take a little longer to lock, but I'm stopping quicker. Does that make sense?
 
Guess I am too old and not strong enough.
 
Ah wait... I'm talking discs. Jack has the drums in the front.
 
Yeah, sorry, Mine's a '63 Midget so first year of front discs I believe. I guess I'm just not convinced it's braking as well as it should. I have no excuse though, I'm only a few miles from University Motors, home of John Twist. He'd know. Moot point again, took my 7 year son for a cruise and and ice cream. Just now checked the oil spots and was shocked to see a full blown Exxon Valdez event going on.
Darn.
 
What's the proper push rod length at the MC? I'm getting "blowby" where the juice is coming back into the reservoir and I'm wonder if the piston just isn't sitting in the bore at the right spot. Brakes work pretty good but fluid finds it's way out the vent on the MC cap (and eventually on my foot). Either that or the valve that came in the MC rebuild kit is wrong or put in wrong, since it was not the same as the one I took out. No seal on it, just a plastic thing. (kit from VB if it matters).
 
It is possible that valve is defective! If you still have the old one and it is in good shape you might try switching back to it and see if there is an improvement! Check the push rod adjustment first! The push rod should be adjusted so that there is just a smidgen of free play (1/32" or .8mm) before it contacts the piston!
 
The old valve had a seal with it, not in good shape, new valve was just a plastic thing, maybe I was supposed to use a seal of some sort with it? I confess I wondered how this was supposed to be a "valve".
 
jvandyke said:
What's the proper push rod length at the MC? ).
Click to expand...

Different years had different lengths! i wish i could tell you that i knew which one was what, but IF i recall correctly, the 3/4" bore ones that come with disc brake cars are slightly Longer than the earlier ones.

OK, i just went down and measured my spares. 3 5/8" in length.
 
I'll have to check the length sometime. I did notice after this last rebuild (I honed the bore and put in another cup seal on the brake) that the piston was pretty hard to move, good I thought, maybe not if the spring isn't strong enough to push it back out again? Here's a picture for your enjoyment.
mcpushrods.jpg
 
Looks reasonably close to me. But my got is that nasty. I bet you get your hands all dirty working on that. Hehe.
 
Nasty is not the word for that. If you have problems you know where to look for sure.
 
I sure don't like the looks of the return spring on the brake side!!!...Stretched and not even hooked!!
 
I looked at that but I think it is hooked, just bent wrong and twisted to the side. But I agree that needs replaced.
 
Try the trick mentioned earlier in the thread where you replace the brake line coming out of the MC with a bleeder nipple. If you get a hard pedal, the problem is not in the MC. Seeing fluid move when looking down through the filler cap is normal. On my 59BE, I could also isolate front brakes from the back by doing the same test at the T junction of the brake line. For me, the soft pedal problem was isolated to the rear brakes. Not having much luck bleeding, I ended partially disassembling the brake mechanism and using a screwdriver to manually depress the cups in the wheel cylinders to get the last bubbles out of the system. The MC piston is so small it does not move much fluid so any slop in the brake drum to shoe adjustment will (and did)cause a problem in getting enough fluid moved to expel the bubble. I set the drum to shoe clearance to where I could hear it grind a bit. Even setting it up this way, I ended up putting new drums on to better match the diameters of the drum and shoe. Mare sure the emergency brake adjustment is not playing a part in this adjustment. The shoe adjustment helped a lot, but only after driving a bit did the brakes start working correctly. I'm thinking the rebuilt calipers were really stiff in their bores and finally worked free or better seated themselves on the rotors. The car stops great now. It still leaks a bit of brake fluid out of the right rear cylinder (thanks VB), but that is a job for this winter.

Just to show how fickle Austin Healey hydraulics are, it only took 10 minutes to bleed the clutch.
 
I am almost out of threads for adjusting the emergency brake. Have done shoe adjustment too of course, tried to go by the book. The fluid moves violently enough to come out the vent hole in the cap, that can't be right.
 
Jacks trickie trick. Get a short peice of pipe or tube or. slice it lengthwise on one side. Back off the adjusting nut just inside the tranny tunnel, slip your new spacer over the cable, retighten the nut untill you have the brakes adjusted properly.

About half inch would be about the right length I should think.

Gota think outside the box on some of this stuff.
 
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