How to check a M/C for a residual Check Valve

[mr. fix it]

here’s The scenario
I gave upgraded my drums to a full 1973 brake disc/ drum on the 66 Polara last winter

I have a decent pedal but it is lower than I like
I can pump the pedal and the pedal comes to a higher height as compared to a single pushing of the brakes
I adjusted the tears thinking that the rear drums needed to be adjusted to get s good pedal height
Not the case here
So I’ve read about the residual check valve helps this situation
My question is that since I am running a rebuilt 1973 M/C it should have the valve built into the M/C
I have also heard that Cardone has removed these during the rebuild process sometimes and not reinstalled it in some cases

Is there a simple way to inspect the MC to make sure it is present?

 

[Davea Lux]

First off, I am assuming you are satisfied that the brakes are properly bled. The check valve can only be accessed by disassembling the master cylinder. The FSM should show an exploded view of the master cylinder so you can determine if the master cylinder required a check valve. If the brakes come up after pumping, I think that you probably have the travel rod set too short. This is the rod that goes into the back of the master cylinder from the booster, it has an adjusting screw on the end that goes into the master cylinder. The FSM shows how to adjust it, you should have about 5/8" to 3/4" free play on the pedal before the brakes start to engage assuming everything is correct on the rear wheel adjusters. The Cardone brake boosters are crap right out of the box most of the time and they have not stocked the correct booster for this conversion for several years. The correct booster for this conversion application is the '68-'71 Bendix dual diaphragm booster. The drum brake booster should not be used with disc brakes as it has less boost. The '66 Polara did not come from the factory with a brake portioning valve, did you install one? If so, if it is the adjustable type, you may not have it properly adjusted, this can cause erratic braking although usually an improperly adjusted portioning valve will not cause a low pedal condition, just locking of either the front or rear brakes.

Dave

 

[mr. fix it]

Hi Dave
I have everything but the dual diaphragm booster including the oem distribution block from the 73 Newport
The brakes work great other than a quick pump of the pedal to bring it up to a higher level
If I don’t pump it once then the brakes still work but just a lower pedal
The single diaphragm booster is giving me a firm pedal feel with no concerns of stopping the car
It just doesn’t offer as much boost as a dual diaphragm booster

 

[70NEWYORKER]

Real simple to check.. get a spray straw from a can of brake clean and insert it into each port (see pic). If the one going in the drum side inserts as deeply as the disc side the valve is missing. I went thru 3 masters a few years ago to get one with the valve. A missing valve will give you a low pedal. Double pumping can raise it up.

 

[Davea Lux]

View attachment 194630 Real simple to check.. get a spray straw from a can of brake clean and insert it into each port (see pic). If the one going in the drum side inserts as deeply as the disc side the valve is missing. I went thru 3 masters a few years ago to get one with the valve. A missing valve will give you a low pedal. Double pumping can raise it up.

Good idea, had not heard that one before. Now if only it could tell us if the nimroids at Cardone installed it in the right direction. LOL

Dave

 

[mr. fix it]

View attachment 194630 Real simple to check.. get a spray straw from a can of brake clean and insert it into each port (see pic). If the one going in the drum side inserts as deeply as the disc side the valve is missing. I went thru 3 masters a few years ago to get one with the valve. A missing valve will give you a low pedal. Double pumping can raise it up.

I had wondered if I would be able to insert something like this.
Thanks for the advice!

 

[mr. fix it]

Ok, so since my last post, I have adjusted the push-rod with I would estimate about a 75% improvement on the travel distance of the pedal.

I don't have time to check today for the residual valve (family outing calls.)

I will pick up a residual valve this morning as a backup since the only in stock retail outlet is about 20 miles out of town and not great hours of operation for the working class slob 8-5:30 M-F 9-12pm Saturdays

After this if it is still not great then I will recheck the rear brake adjustment ( Did a few times already) and then replace the drum booster with a dual Diaphragm booster.

 

[Polaraco]

So I woke up an old thread.

Does anyone know how to remove the residual valve from the master?

 

[Mike66Chryslers]

So I woke up an old thread.

Does anyone know how to remove the residual valve from the master?

I posted instructions with pictures in this thread.
This booster work with dual reservoir master cylinder?