New Booster master cylinder frustration

[barnesjtsl]

I've bleed brakes on various vehicles MANY times. I always use the method where I have a canning jar with a hole in the lid and the jar about 1/4 full of brake fluid with a hose going from the caliper bleeder valve to the jar and submerged in fluid. Open the reservoir make sure it's full of fluid then get in the car and pump the brakes until bubbles quit coming out of the hose in the jar. This methods has always worked perfectly for me, never any problems.

I purchased a new booster and master cylinder. Took the old out and put the new in. Like a fool I forgot to bench bleed the master cylinder. When I hooked everything up refilled the reservoir and bleed the back brakes and they bleed perfectly, no problems. Passenger rear first, driver rear second. Then went to the passenger side front and started bleeding and nothing came out into the jar, only a couple of bubbles then nothing. Then like the genius I am it occurred to me that I hadn't bleed the master. So I bleed the master cylinder in the car. Installed a bleeder kit connection from the passenger side connected it to the hose and then put the hose in the full reservoir. Pumped the brakes slowly, holding it all the way down then letting it out slowly until no bubbles were coming out of the hose in the reservoir disconnected the bleeder kit and connected the tube back up. Then did the same thing on the other side.

Did no good. I still have nothing coming from the master cylinder to either of the front calipers when proceeding with the bleeding process I described above.

One thought. When bleeding the master cylinder, do I need to bleed all 3 of the connections at the same time? I only did the two for the front?

Any thoughts?

John

[spider2081]

With the car fairly level if you open either front bleeder valve does the brake fluid run out simply from gravity??? If there is a lot of air in the system it could take a few minutes for the fluid to start running from the bleeder
If the fluid does not flow out on its own, you may have a blockage somewhere.

[barnesjtsl]

I have the front end jacket up right now.

So is what you are saying is that even if the master cylinder isn't properly bleed then if I open the front bleeder valves and leave the reservoir lid off that fluid leak through the system by gravity?

Thanks for the reply.

John

[RRoller123]

Yes, I bleed my brakes this way, it takes some time, but it doesn't make a mess, and is very controllable.

[spider2081]

So is what you are saying is that even if the master cylinder isn't properly bleed then if I open the front bleeder valves and leave the reservoir lid off that fluid leak through the system by gravity

Yes it will. I like to have the car fairly level when I do this but I don't think that makes much difference.
I usually gravity bleed the brakes one caliper at a time before any other form of bleeding.
Another thing I do that saves bleeding time is to top off the reservoir and then seal it with something like "press n seal" or thin sheet plastic. I actually have a spare cap with a solid piece of cardboard in it that I put on top of the seal. This prevents a loss of fluid from the reservoir when replacing parts. Then after parts are replaced remove the seal and open the first bleeder and let all the old fluid gravity drain out. Once the old fluid is gone I then gravity bleed the other calipers one at a time. Brake fluid is cheap and the system should be purged every couple years anyway.

[DieselSpider]

What condition are the front brake hoses in? They could be plugged and if they are no matter what you do the system won't bleed.

How long have you had the car and has it been off the road for an extended period of time?

One note of caution is that a number of the original spec brake components on the Spider may not react well to DOT4 or Full Synthetic brake fluids especially the rubber brake hoses.

[kmoses]

I had very good results with a hand type vacuum pump. Put the hose on the brake bleeder fitting and the vacuum will pull the fluid through the system. If you do not get flow this way there is some blockage or the brake hose is collapsing. Start at the caliper farthest from the master cylinder and work your way forward.

[raysorm]

just did brake job 81 spider replaced rotors/pads but did not replace master cly- gravity bleed front and vacuum did well. replaced in rear rotors/pads and copensator with all linkage and bushings but could only bleed old fashion pump assistant would not vaccum bleed. Glad I looked at the compensator in the back as it looked original and rod looked like it may have been bent at one time and there were no bushings left. So but the front should gravity bleed really fast and good. You could reverse bleed. Seen some pumps that you hook up to the bleeder screw and pump brake fluid backwards into the master cyl push air back out to resevior looks like works like a champ on internet vids.

[Odoyle]

Not sure if someone mentioned this, but did you adjust the acorn nut on the plunger rod (on new brake booster) to 1.2-1.9mm stick-out based on factory settings. If that wasn't done when you swapped boosters, that will definitely be an issue. You can reference the old booster if needed.

[barnesjtsl]

Thanks,

Yes I adjusted the plunger. I had to screw it in as far as it will go to get it to match the old one.

Update. The reservoir is still not draining through. When I first installed the MC the rear brakes bleed perfectly. The front brakes I can't get anything out. I replaced EVERYTHING on the front brakes with the exception of the passenger side tube.

I replaced the following:

Both rotors, both calipers, both brake lines, the drivers side tube, the master cylinder and the booster. Before I had replaced all this all the brakes bled fine. I replaced all this because everything was at least 20 years old and looking really bad.

Now the care is on all four wheels in my garage on a flat polished concrete floor. I have both the front bleeder valves open and the cap off the reservoir. It has been sitting this way for 3 days and nothing has drained through. The reservoir is still full and nothing has come out of the bleeder valves?

I'm stumped,

John

[kmoses]

Try this, unbolt the brake fluid reservoir and raise it so that the hoses going to the master cylinder hang down with no bends. Rig up something to keep it this way, carboard box, wood ect. Loosen the brake line nuts on the master cylinder and see if the brake fluid starts dripping and you see bubbles in the brake fluid reservoir. When you see bubbles and brake fluid, tighten the line nuts and try to bleed the brakes.

[barnesjtsl]

Okay, I'm starting all over. Reinstalled the old master cylinder and had the same problem so I took everything out and am starting all over.

So a few questions:

In the front of the booster where the plunger comes out there is a black plastic "cup insert". Is that just for shipping or do I install the master cylinder to it with the cup in place, or take the cup out and throw it away.



Below is a picture of the booster with the plunger sticking out without the plastic cup mentioned above installed. If the black plastic cup is not to be installed, does this look like it is sticking out too far? It is screwed in all the way with the locking nut tight. Is there a way to make it go in further if need be.



Below is a picture of the booster with the plunger sticking out with the plastic cup installed. Does this look correct? The plunger will not go any further in.



Below are two images of the new master cylinder. Do I install it with the Black rubber cap installed or was that just for shipping and it is removed for installation?




Any help appreciated. This driving me nuts.

John is

[spider2081]

The plastic piece that sits in the booster remains in the booster. I think its there to prevent brake fluid from leaking out of a defective master cylinder into the booster.
The Rubber dust seal on the master can remain in place. I have seen a number of cars with out the dust seal but most have them in place when I remove a master cylinder.

I use the tip from a gear lube container on the brake fluid container, this allows me to fill the master cylinder once its installed on the booster before I install the metal lines and reservoir lines. I pour brake fluid into the master cylinder reservoir opening until it comes out the brake line opening. Once the master cylinder is full I connect all the lines.
Does the fluid flow freely out of the reservoir lines if they are disconnected from the master cylinder?

[wetminkey]

You suspected it.
Bench bleed. I've run across this nasty situation before,...
Best of luck. Todd.

[Odoyle]

+1 bench bleed MC
Black seat/cup is there to keep pushrod in alignment when actuated. Best to remove when measuring stickout of pushrod tip. It should extend past the front cover by 0.0408 to 0.0758 in. (1.035 to 1.925 mm) (Factory Manual pg 33-18) Any more or less and you will have issues.