Thanks numbers but my light doesn't even come on, switch broke or not, it lights on start up but that is it. Mine actually is still serviceable for some reason.

 

If you think yours is dirty then take it apart and clean it out. Look at posts 18 and 20 for drawings.

There is also this from 80-86 that may help:

https://www.ford-trucks.com/forums/1...lve-issue.html

 

I was afraid that if I took it apert then I should replace the internal seals. I haven't had the best luck taking apart 35 year old parts that have soft seals in them and trying to clean it. Usually I end up taking it apart then ordering new rebuild kit to fix it right. I worked on it today and it seems to be working a lot better, I think getting the fluid flushed out of it helped as well as tapping on it with a hammer to break some of the gunk loose. It is working better than before, I will give it a little time and see.

 

I would not be surprised if the rebuilt master cylinder is bad. Take the lid off and look through the hood gap as you step on the brakes. If you get a fountain of fluid, it is bad. After getting several bad ones, I quit buying rebuilt. New is not much more.

 

I think it is good. I just did a good bleed, opened all the fittings that would turn on the proportioning valve and I have drove the heck out of it. It is much much better. Still room for improvement, but better. I agree, the reman masters are good for about 1-3 years and you better be replacing them.

I took my brother for a ride and he said thet there wasn't enough vaccuum for good braking at idle. I downshifted the C6 to 1 coming up to a stop sign and that doubled my braking power from the increased vaccuum. I need a smaller cam is the only way to fix that. Too much cam and not enough vaccuum. I can live with it though.

 

A few on my rebuilt master cylinders failed right out of the box. Try to find a check valve and you might help your brakes.

 

check valve, for vaccuum? I have one right on the the fitting that hooks the line to the booster. I check it to make sure it is working often. Thanks thtough. Is there something other that would work?

 

Ok here's the situation F100 experts. 1974 F100 with power drum brakes all around ! Yes It came that way and it's hard to believe. Added a vacuum reserve tank, installed 4 new calipers, which the front ones were hard to find and expensive, adjusted and bled the brakes. Still pulls hard right and the brake pedal goes almost to the floor. The brakes pads are new. Everyone here is stumped. Could it be the residual valve, the proportion valve a miss matched proportion valve ? I know disc brakes were standard but it looks like someone put front drums afterwards and possibly it's miss matched. Does a proportion valve for 4 drums even exist? Any help would be appreciated.

Thanks
Stumped in SC

 

You said you have 4-wheel power drums but mentioned installing (4) new "calipers." (?). I take it you mean you installed (4) new wheel cylinders --drum brakes have wheel cylinders. Disc brakes have calipers.

Brake drums have shoes. Disc brakes have pads.

While the original MC installed on the truck, from the factory, likely had RPVs (Residual Pressure Valves) in the MC ports going to the drum brake circuits, MOST parts stores replacement MCs do not come with them installed these days --even if the OEM MC did.

Pulling to one side could be caused by grease/oil on the brake shoes/friction surfaces of the drum or, the shoes could be adjusted up tighter on one side than the other.

A pedal that is mushy is generally caused by air in the system or, the brake drum shoes are not adjusted out.

Vehicles with all wheel drums don't have proportioning valves. Proportioning valves are used on disc front/drums rear brake systems. An all-wheel drum brake vehicle will have a Pressure Differential Valve.

(In the case of '68-'72 model trucks: The '68-'72 F250 and F350 trucks with optional front discs used the same pressure differential valve as the trucks that had 4-wheel drums. [F100s prior to '73 didn't come from the factory with front disc brakes]. The only difference being the '68-'72 F250/F350 disc brake trucks had a stand-alone metering valve plumbed inline to the front disc brake circuit).

In '73, the metering valve to the front discs, proportioning to the rear drums and pressure differential sensing between the two brake circuits were all integrated into one valve body assembly on the trucks.


IF your truck was factory equipped with drums, you should have a pressure differential valve. IF it came with discs on the front, it should have a 'combination' valve. IF the front brakes were originally discs and later swapped to drums, and the combination valve was not swapped for a pressure differential valve, then you may experience some odd braking application. --even so, the pedal shouldn't have as much travel as you describe.