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missing pressure build up in brake system

matgmatgMember
Team Hi sorry an other of the mysteries (at least I did discover... ). I cannot get PRESSURE on the brake system ....

Starting point:
1) all new tubes, fully empty break system
2) NO Brake pressure balancer (front vs back)
3) Adapter/Booster applied (figure))
4) all O rings within the main cylinder look good to me (figure)
5) Main cylinder is NOT original I know, it supposed to have worked (I never tried it)

Situation:
a) the movement of the brake pedal I have adjusted to app 40 mm/1.6inch , so the push rod coming out of the Vacuum container can go FAR into the Break main cylinder.
b) The over stand of the push rod coming out of the Vacuum container has an over stand of app 8mm/0.3 inch at no action, hence the main cylinder hast already some push in at ZERO Brake pedal move, app 5mm/0.2 inch
b) the brake pike system got flushed via a vacuum pump
c) I cannot build up any pressure by pushing the brake pedal, neither by LONG movements nor by short movements.

Help..I am stuck and I missed today my date for the MOT/TÜV...a mess...(in nice words..)

Matthias

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rockyrockyMember
Hi Matthias -

Did you “bench bleed” the master before installing it?

Another idea might be to try and use vacuum from the wheel cylinders to pull fluid into the master.

I hope the true expert can chime in on your question. Good Luck

Rocky

PS. That’s the same master as I am using, so it should work if you can get it to pump fluid.
jfb05177jfb05177Member
quote:
Originally posted by Rocky:
I hope the true expert can chime in on your question. Good Luck
Rocky


Well, I ain't He...But something it might me

quote:
Originally posted by Mat_G:
b) The over stand of the push rod coming out of the Vacuum container has an over stand of app 8mm/0.3 inch at no action, hence the main cylinder hast already some push in at ZERO Brake pedal move, app 5mm/0.2 inch

Matthias


I am "thinking" the main cylinder push rod has to have a gap between the vacuum booster so that the cylinder can return all the way and only then will it allow fluid from the resivoir to enter the cylinder

Now, to pull fluid from the resivoir into the cylinder depends upon the vacuum that is created when the full down cylinder is released. Having an system empty of fluid (but full of compressiable air) means a VERY small vacuum is created to pull in fresh and only a very small amount of air is burped when pedal is held on floor for the bleed

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bosswrenchbosswrenchMember
As JFB mentioned, a host of problems comes with adapting brake master cylinders. Do you need to adjust the power booster brake rod? Its easy- unbolt the master cylinder from the booster but do not remove it. If the master cylinder pops away from the booster, measure the gap thus produced as best you can, and shim the master cylinder to the gap plus about 0.010". Bolt down and try your brakes.

In some master cylinder adapter blocks, there's a teflon guide bushing that fits way too tightly; it won't prevent brake use until things heat up in the front trunk. Then it can contract on the rod, squeeze it tightly and prevent the brakes from relaxing after use. Ream the plastic bushing out so there's plenty of clearance. I've done this for others on the road using a Swiss Army knife blade- the precision is not critical.
R rrs1Member
I had a problem similar to this, drove me crazy for days. I did have a pedal, but it was soft. I was solely focused on the master cylinder, and push rod adjustment. I finally decided it couldn't be the problem, to test, I plugged the ports to the MC, I then had a hard pedal, so one at a time, I disconnected each brake line to the caliper, and plugged it. I found that I had the wrong fitting from the brake hose to the hard line. There was no noticeable leak, but enough air was getting in there to prevent pedal firmness.

Point is, it can be something else in your system!
joulesjoules"Racing is Life, anything before or after is just waiting" - Steve McQueen
I'd agree with all that has been suggested so far, bench bleeding and the pushrod. However, the dimensions quoted might not be valid for an aftermarket brake master as the plunger is not necessarily at the same dimension. I had to actually machine a new pushrod end for one application.

Julian
panteradougpanteradougMember
It sounds like the need to bench bleed the master cylinder to me.

These things vary in sensitivity to this need but there is a lot of documentation in various shop manuals to recommend that you do this first.

Do it on the car though. Just make up some tubing that curves around back into the reservoir. It only takes a couple of pumps to do it.

I also find that if you use a vacuum pump on the individual wheel bleeders, that helps a lot as well.

Considering how many masters I've damaged trying to pump up the pressure, I use the vacuum pump regularly now as a precaution.

Buy one. They are worth the "investment".
matgmatgMember
Tx Team I will jump on it tomorrow morning.

Action:
1) adjust the push rod so that the cylinger goes back to "zero"/ to the stop given by the retainer ring when the pedal is released (by shiming as Chuck suggested).

2) bleed the main cylinder by "return" tubing or worst case on the bench

..and draining is done by a vacuum pump..is nice stuff and clean, no fluid on the floor or elsewhere. Smiler

Danke....I need desperately success as all other stuff is ready.!

Matthias
jfb05177jfb05177Member
just my thinking on how to streamline the work;

after you adjust the MC rod to allow it to go to zero and thus open fluid path to the resevoir, THEN using vacuum at the calipers to pull fluid from the resevoir, that should prime the master cylinder without having to perform a seperate bleed just for it


My "thinking out side the box" has me wondering....

For a new "dry" system, If one depresses the break pedal to isolate the resevoir and pulls vacuum on the calipers, would the MC seals hold so that one could watch to see if the vacuum holds to verify fittings are not leaking. the front and back circuits would need to be checked seperately
matgmatgMember
OK ..no success after rework today Monday..

1) adjusted the push rod comming from the pedal pushing the cylinder to VERY smal gap only

2) "vacuumed" the both rear and front container of the main, lots of air came out

3) vacuum pump driven bleeding of the back and Front..again

..NO Pressure...

per PanteraDoug I will go for a new one now.

The Ford code is E2TA 2155 in ALUMINUM

..CAN ANYONE TELL ME FROM WHICH FORD MODEL IT WAS? As then I have more options to shop..

TX Matthias
rockyrockyMember
Got this from a Pantera Expert. Note the disclaimer at the bottom, but I believe it to be very credible.

quote:
The casting number on the master cyl decodes to a Ford truck, most likely a Ranger (1983-1985). Replacement cylinders are steel, not aluminum.

Bore size: .9375" (15/16")

Line thread size: 9/16-18, 7/16-24 (power brakes), NAPA #M2481

Line thread size: 1/2-20, 3/8-24 (manual brakes), NAPA #M2482

The bore size of the stock Pantera master cyl is .875" (7/8")


The Ford Ranger has front disc and rear drum brakes. Typically, drum brakes have a residual check valve (in the master cyl), and disc brakes do not. Since I have never had one of those Pantera vendor supplied Ford masters to disassemble, I don't know if the Pantera vendor removed the residual check or not. It's easy to remove.

If you choose to go to a 1" bore master cyl, a master from a 1986 Ford F150 should work, but the hard lines are on the opposite side from the one that you have now.

Bore size: 1"

Line thread size: 9/16-18, 7/16-24 (power brakes), NAPA #M2405

Line thread size: 1/2-20, 7/16-24 (manual brakes), NAPA #M2408


If you decide to change your master cyl, you can mic your existing tubing nuts to determine the line thread size that you have, and then go shopping. Master cyl tubing nut adapters are readily available if you have to change size(s).

All of the above sizes were pulled from the NAPA website. YMMV

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matgmatgMember
I think the adapter/booster ONLY adapts the LEMGTH of the BOMB/Container with its push rod lenght for the Master C.

With my Booster I followed advise to have VERY little play betwenn pedal push rod coming out through the BOMB and the master cylinder entry level.

Cylinder in Master is now at NO PEDAL move at ZERO STATE (retainer ring level!!!) (think this is what I understood from Chuck/Bosswrench's statement).

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