fhorta

Hello. Didn't see any previous posts. Going to receive new MC and I guess I will need to bleed on a vice or something . Is there how to instruction, will need certain type tools, ? So does this mean that no more bleeding will be required besides the MC...no need to bleed actual brake lines at the wheels once MC is installed?

cruiser54

fhorta

Thanks!

oldnslow

Here is a tip I use on my old VW's, as they are drum brakes on all wheels, so this is only for your rear wheels.

Before you start the " pump and hold" routine, adjust your drum brakes all the way out, against the drums, firm. This will take out any "slack" in the fluid in the brake lines. In other words, no brake pedal travel will be wasted on the travel of the brake pads as they move towards the drum. Then do the ol pump and hold routine. After a couple of pump and holds, you should get a substantial pedal. Leave em like that until you are completely done with all four wheels. The front are disc brakes, and they don't have a return spring pulling the pads back, so they are always where they need to be.

BUT, remember to back the rear shoes off a bit when you are done.

Roler

You can buy the little bleeder kit online which sometimes comes with the new MC.
Otherwise you can do it like this- without the kit (skip to the 4:00 mark)

dmoe69

I haven't used this tool yet, I have a booster on order, but I've had issues with the gap between the master cylinder and booster on both my '66 Mustang and my '88 XJ. I believe this tool will easily give positive assurance the booster rod is set correctly prior to reassembly and bleeding. It really sucks to find out you have a booster rod dimension problem after you've done all that. This particular one can be found on Amazon for around $15. It is called "brake booster adjustment tool".

fhorta

Hey guys. I'm still on this project. I instslled new booster and bench bled the mc and installed it. I then did the old pump and hold routine with rear brakes first and am not having success; pedal does not get stiff. It does seem to but when I start the car and press brake, it just gets soft and sinks to bottom. I noticed after several pumps of the petal that there is small leak between mc and booster. Is this norma ? I took out mc again, went over bench bleeding again
but seemed I could not take anymore air out as when I pushed in rod, itbwould not go in more than maybe half an inch and it was pretty hard and with no bubbles.

When bleeding brakes, I see bubbles, but they diminish after pumping. I.move on to the next and same thing..in the end pedal still soft. I got the bleeding tool kit from O'Reilly s. I will try it next. But am worried at this point about that small leak. I heard also that there some rubber hoses as part of the caliper that can suck air too? One more thing, I noticed some brakes fluid leaking out the bleeder screw that I installed new cuz old one stripped. I tightened pretty good but should I put thread sealant , or it should not need. Any comments, suggestions, ideas greatly appreciated. I'm thinking about returning this mc and getting replacement, start over. Thanks in advance

fhorta

Well, so far looks like there is a difference in the thread of those bleeder screws..fine and coarse. The replacement bleeder screw I got thread is fine and original is coarse...ughh!!this is supposed to be easy project!! No wonder the brake fluid was still leaking; threads were different so not sealing.

Roler

Yes the pedal going floor is usually a leak anywhere in the system causing you to loose pressure.

To answer your question: no it's not normal to leak between MC and booster. Or at least it shouldn't.

Air in the proportioning valve should not be overlooked and it has it's own bleeding procedure.

The bubbles you bleed out also get smaller if you press the pedal multiple time.

Bleed in the correct order:
MC bench bleed
Proportioning valve asssembly
Brakeslines (the most common sequence being: furthest from the MC bleederscrew first, than other rear, then passenger front and driver front last)

fhorta

Thanks all for the replies. I took suggestion and ordered replacement brake cylinder instead of messing with finding this elusive original size bleeder screw; it was only about $7 for cylinder.
I also have the bleeder kit with pump. Can i use this to also bench bleed? I would rather not use the push in method with screwdriver and risk pushing too far. I returned the new MC and getting a replacement.

Roler

No the kit for the MC is different: it will need threaded plugs. The 1st time I bought a new MC they came with it. I lost them when I had to redo a breaksystem overhaul recently so bought a kit online- cheap and different adaptor sizes and threads included. Look online.

Don't be concerned about the push method: it takes quite a bit of force to push it in even a bit and you can't go 'too far'.

fhorta

I got bleeder kit. New Master cylinder too. After inspecting booster though, the original's push rod is about one inch longer than one i had bought..did I order wrong one?? I see a post here about measuring that rod, but I already ordered the booster so too late to measur it. The rods are being measured with rods being pulled out all the way as far as they go and without countingthe tips at the end, which are adjustable but only so much. The original measures about 2 and 3/4 inch and new one not even 2 inches..about 1 and 3/4 only. Will this cause an issue in brake operation?

dmoe69

6th post, this thread. There is a jam nut on the booster's rod. Hold the rod, break the jam nut loose. Turn the tip until it is the correct length, tighten the jam nut. Some say that you should take the measurement of the booster rod's length with vacuum applied. That could be difficult. My "66 Mustang has a vacuum pump for the brake booster because the camshafts lobe profile doesn't make enough engine vacuum, so I can run a vacuum hose to the Jeep's new brake booster. Whether or not vacuum is actually necessary for the measurement...maybe someone else can chime in.

fhorta

Thanks. I don't have the that tool. I measured depth of mc piston and itss at just under 1.5 inches. So I figured that with booster rod pushed all the way back as far as it goes , just adjust it out , or in, to same length of cylinder measurement, which is just under 1.5 inches. Is that about right procedure?

Roler

I've not used that tool (or even knew it) but wish I had because it would make the job a LOT easier The clearance you need is ridiculously small to achieve by eyeballing it. You can calculate but we're talking 0.02 inches or something.

I measured and used a 'shim' in de MC end . Then trial fitted the MC to the brakebooster which made the MC barely touch it ( 0.02 inch . Then removed shim and refitted everything. Not overly happy with this method but it worked.

That tool would make it a two minute job.