Master Cylinder Hatred

[sketchman]

I just did a MC(3 times now for nil) and "bench bled" it on the car every time before I hooked it up to the system. I assume when you connect lines and run them to the reservoir you should be able to just pump away and get all the air out?

This doesn't happen for me. Fluid goes up the tube as you push in the pedal and right back down when you let off it. The only way to stop this is to push in the pedal and then hold 2 fingers over the ends of the tubing before you let off the pedal. Otherwise you get nowhere. This is my 3rd MC. All had the same problem. This last one was taken off a scrap 88 and it works the best, but still not as it should. Am I missing something? With the current scrap MC, I can bleed the system for an eternity and you still get a pedal with absolutely no feedback and no braking till an inch off the floor.

[htchbck]

Unless you have bleeders with check valves built into the (the stock ones do not have this) then everytime you let off the pedal it will just suck the fluid back. In order to get it to suck fresh fluid in from the MC you have to keep it from pulling the fluid in the tube back in. Start by OPENING the bleeder, depressing the pedal about 3/4 way, then CLOSING the bleeder before the pedal is released. You should have one person inside the car and one at the bleeder screw. If my description doesn't make sense then just get a Haynes manual and use the description in there. Or if you can find a set of "one man speed bleeders" that work, you can use those to do it by yourself since they have a check valve that only lets fluid push out, but won't suck it back in. I usually just take the factory bleed screw out and put in the speed bleeder, crack it just a little, hook up a piece of tube that goes into an empty just, and start pumping away keeping the MC full of course. Every once in a while I check the tube an once the fluid runs fresh and clear, I take on the speed bleeder and reinstall the factory bleed screw and move to the next wheel till I'm done Hope this helps!

[sketchman]

Once we got it bled enough to connect it to the car, I was under turning the wrench while someone else pumped the brakes. It seemed like forever, but I still end up with the sponge pedal, no matter how much I bleed it. It was running clear as it should, but it felt no different than if you filled the mc full of air.

[eurotiva]

^ you have a leak somewhere.

[sketchman]

^3 different MCs. 1 new, 1 reman, 1 scrap. You can pump for a year and no fluid will be drained from the res unless you open the bleeder on a caliper or cylinder and bleed it like normal. I'm near certain nothing is leaking.

[91_festy_Gl]

Start bleeding the front first, perferably closest to the MC. I know I know everyone says to do it the other way but I went through this same things and found that if you bleed the front first, the rears will build pressure. After finding this out I always bleed them like that on a festy and works everytime. Oh ya are you near beckley or oakhill wv?

[eurotiva]

Bad proportioning valve. ?

[sketchman]

Start bleeding the front first, perferably closest to the MC. I know I know everyone says to do it the other way but I went through this same things and found that if you bleed the front first, the rears will build pressure. After finding this out I always bleed them like that on a festy and works everytime. Oh ya are you near beckley or oakhill wv?

I'll try this as I have been following the Haynes Manufail and it does say to do it like you mention that everyone says is correct. Hope it works.

I'm around 2 hours from Beckley.

[91_festy_Gl]

See not to many people know it but on the MC, the port for the rear doesnt push the same amount of pressure as the front because I car relys more on the front for stopping. I went through 3 MC's testing the pressure and sure enough they were all the same. Once I noticed this I went to the front and bled about 3 times each before moving to the back. Once I got to the back I bled each once and the pedal is rock hard. Thats even with the aspire swap. Same goes for the festy setup.

[Pu241]

See not to many people know it but on the MC, the port for the rear doesnt push the same amount of pressure as the front because I car relys more on the front for stopping.

I thought that the proportioning valve took care of distributing the hydraulic pressure not the MC itself?

[speedoholic]

I thought that the proportioning valve took care of distributing the hydraulic pressure not the MC itself?

That's why I thought it was called the "proportioning valve".

[Biff]

If it is still not bleeding, I would use a vaccum pump to pull the fluid through the lines.
I have a small hand held vaccum pump specifically for this.
Check it out, with any luck it might save more fustration?

[91_festy_Gl]

All the valve does is divides the fluid to all 4 wheels, thats it. The fluids pressure comes from the MC itself. Pressure doesn't change from the valve to the wheels, it stays the same from the MC through the whole system. Seriously check the pressure on the front port on the MC and compare it to the rear port. You will notice a diffrence in pressure. Thats where the braking ratio comes in. Im not totally sure but I believe its around 60/40, 60% front and 40% rear. I havent went into a in depth figure on the ratios but from my calculations it should be somewhere around there, but ya the proportion valve gives each line to each wheel, fluid.

I spent a whole week swapping MC's, calipers from 3 diffrent cars, and proportion valves testing diffrent combos.

[sketchman]

You're like Scrubbing Bubbles, except you don't go away afterwards. :shock:
That means.......
You're better than Scrubbing Bubbles? :shock: :shock: :shock:

Seriously though. Good stuff to know.

[91_festy_Gl]

Did you get anywhere with this?