brake help needed.....

Hi Guys,

Trouble with the brakes on my ride:

Front: early ford hydraulic units (with the adjustment bolts top and at the bottom)

Rear: for frieghter truck (early F1-ish type truck). The have a star wheel for the adjustment.

Master Cylinder: 1972 Ford Falcon

Here is the wrap. Ive adjusted both and front and rear brakes, they seem to be set up well. Lots of lining left on the shoes, no fluid leaks etc etc. I've bled the system.

Now the pedal goes straight to the floor. You have to pump the pedal about 4 times before you get even a hint of pressure it seems. The brakes used to lockup before you hit the bottom of the stroke but has been getting progressivly worse. When we topped up the fluid level after bleeding, we noticed the fluid had bubbles or froth on the top.

I'm guessing that it is the master cylinder but has anyone else got any ideas?

Danny

 

Get it power bled, you got a giant air pocket in there!AL

 

Did you bench bleed the master cylinder before you put it on? If not you can do it on the car. make some temporary brake lines from the m/cyl ports to go up, over and turn down into the resevoirs below the fluid level. Slowly pump the pedal until all the bubbles disapear. Reconnect the brake lines and bleed as usual.

 

hey guys,

ahh ok. no i didnt bleed the master cylinder! this is a complete system already installed on the car.. so I didnt know if i needed to bleed the master cylinder.

ok to ask some more stupid questions:

1. Can you use flexible hose to make the return lines from the port to the resevoir?

2. When you pump and the bubbles disappear, wont air be sucked back into the master cylinder when you disconnect the hose or do they have one way valves?

3. Is there a way you can bench bleed on a err.. bench, or is it just the same technique?

Thanks again for your help guys, its much appreciated.

Danny

 

Yes we have m/cyl bleeder kits with plastic fittings and hoses. Some m/cyls come with the plastic fittings and hoses. I put the m/cyl in a vise and "bench" bleed it with a phillips screwdriver. whichever is easiest. Any air bubble at the port can be bled at the port or it will travel down the line and be eliminated at the w/cyl. When you get the lines reconnected, pump it up and crack the fittings at the m/cyl.

It's very hard to get any bubbles out of the piston area of a dual m/cyl on the car. Bench bleeding eliminates that hassle.

 

Hi Tommy,

Thanks heaps for your help. If I take the master clinder out to bench bleed is there any easy way to see if the cylinder itself is damaged or needs replacing? I thought I may as well check it since its out.

Thanks again!

Danny

 

Is this a new system, as in never been used, or is it a prevoius used system that devoloped a problem?

It sounds like air in the lines, if the system has not been used before you probably have air in the line that needs to be blead out, is the master mounted under the floor, or on the firewall?

If the system has been used and devoloped a problem, I would suspect a master cylinder problem.

A bad master cylinder usually has black gunk in the bottom of the resivor. They can also leak out the mounting surface piston bore, look for evidance of brake fluid there. either condition exists I would replace the master. Be sure to bench bleed the replacemnt master or you will be doing it again shortly. Gene

 

hi guys,

Its an existing used system thats developed this problem over time.

The pedal couldnt go half way down before the brakes would lock, then it was almost to the floor, then it was you needed to pump it once and it would lock up. Bleeding the system in the past made an improvement but it quickly became worse. When we bled the system last night, it made it worse to the point where you need to pump the brake at least 4 times to build any sort of preasure.

I might grab a new MC and bench bleed and install just to remove that piece from the equation. Could it be residual valves?

Danny

 

I think your on the right path.

If the master is mounted under the floors, residual valves could be bad. If the master is mounted on the firewall there is no need for residual valves. Gene

 

I think your on the right path.

If the master is mounted under the floors, residual valves could be bad. If the master is mounted on the firewall there is no need for residual valves. Gene

 

hey mate.

yeah the MC is under the floor, right under my seat. I'll need to work out whether the MC has intergral residual vlavles or not. I couldnt find any inline with the brake lines. If it is intergrated into the MC i'll def replace the MC as it will take both out of the equation.

Danny