Residual valve needed or not?

[Hackerbilt]

I found that on MY T, I was having an issue with a double pump being required every time you tried to brake.
Multiple attempts and multiple styles of bleeding was tried before I bought the car but the problem always returned...quickly.
I checked it out when I got it and decided that the problem wasn't air sneaking into the lines, but was actually the pistons themselves retracting far beyond the designed limits of O ring deflection, which is the only movement usually seen at the piston. (Disregarding the piston creep that goes along with the pads slowly wearing) I decided to try the RPV's and got an excellent brake that never failed after. Some cars will need them (perhaps due to looser tolerances in various hydraulic parts in the system) some won't. It is what it is...

Brake systems are not a "closed" system...until you actually press the pedal. They are sealed from air and moisture by the bellows in the cap but fluid is free to flow back and forth until the pedal is pressed. If this were not the case you wouldn't be able to push back the pistons at the calipers to install new pads. When you push back the pistons the fluid volume in the master cylinder increases as the fluid is displaced back thru the feed hole at the bottom of the reservoir. Pushing the brake pedal moves the master cylinder piston past the feed hole and the system becomes closed so that actual pressure can be applied to the calipers. (or wheel cylinders whatever.)

 

[old round fart]

Also a spongy pedal can be traced back to the through the frame brake line fittings. The whole is sized for the fitting size on each end. When you put the fitting in you have a small air space that is very hard to bleed out. Don’t remember who makes a fitting to minimize the problem you just have to check around.

 

[fletcherson]

I had issues on my old f350 wrecker. After going back through everything and replacing parts, bleeding, etc, turned out to be one caliper hanging up on the bracket, which allowed it to flex. That allowed just enough fluid movement to overpower the master travel. It was not much movement, but the dual pistons use a lot of fluid to move a small amount. It was maddening trying to find that problem. As simple as brakes are, they can be a real pita at times.

 

[T-Test]

Now you know why MOST people use a GM M/C and front calipers.

 

[fletcherson]

Now you know why MOST people use a GM M/C and front calipers.

Lol! Actually, the ford 3/4 and one ton brakes work very well. I just had a stupid attack and overlooked the issue. I didn’t anticipate that heavy caliper bracket flexing. They will put you into the windshield if you get heavy footed now. I’m embarrassed by how much time and effort I invested into that problem. That’s the price for letting stuff sit unused for too long I guess. It was eye opening to me how much fluid/m/c travel is required to move the dual piston calipers a relatively minimal amount. Machine advantage has a price.

 

[T-Test]

Hindsight is and always will be 20/20.

If we could do what we use to do, it would be worth millions today.


Now where did I put that 9/16 socket?

Ford---found on road dead--- wrecked--- no brakes!!!

 

[Neshkoro]

Ford:
-found on roadside dead
-first on race day
-fix or repair daily
-
-
There must be more!

 

[Kevinrevin]

Ford:
-found on roadside dead
-first on race day
-fix or repair daily
-
-
There must be more!

F@#$ing Old Rebuilt Dodge

 

[Neshkoro]

By the way, I'm not knocking Fords. I've owned my share of them over the years.
1965 Galaxie
1966 Mustang
1930 Model A Tudor
1979 Mustang
Another 1930 Model A Tudor
I won't count the two T Buckets. There wasn't much Ford stuff in either of them!
Not so many car names you can have fun with, like Ford!

 

[Island Girl]

By the way, I'm not knocking Fords. I've owned my share of them over the years.
1965 Galaxie
1966 Mustang
1930 Model A Tudor
1979 Mustang
Another 1930 Model A Tudor
I won't count the two T Buckets. There wasn't much Ford stuff in either of them!
Not so many car names you can have fun with, like Ford!

How true that is!

I spent a week one day trying to come up with something for Pukejoe, er Peugeot

 

[fletcherson]

I have love and hatred for every brand. Some are better in certain categories than others, certain years and models, but they all have room for improvement. I’ve been stranded by all of them a time or two.

 

[TheYeti]

I had read about the use of residual valves many times but wasn't sure if they were worth the extra work to plumb.

My dad has a roadsmith trike conversion on his harley. They used this funky brake setup to achieve some mechanical advantage. They used the original master cylinder at the foot board that was plumbed to a slave that had the same size bore as the original caliper, that slave was linked up to push on a bigger master cylinder that was feeding 2 dodge omni calipers. The big master blew out and I didn't like the setup anyways.. looked really over complicated and would barely even create a drag if you STOOD on the pedal.

I wanted to plumb straight from the bike master cylinder to a T that split to feed both rear calipers. I found an after market master for it that was 3/4 bore. Great! but it doesnt have much travel to fill those calipers.. that could cause a problem. I decided to run a 2lb residual valve right off the master to eliminate all that fluid from running back to the master every time you let off the pedal. This setup proved to be a winner. It starts applying brakes almost immediately when you set your foot on the pedal and will lock them both up within 1.5" of travel with little to no effort on the pedal.

So that being said, yes I recommend residual valves. I will be running a 2lb to my front discs and a 10 lb to my rear drums when I get to that point on my T. Keep the pedal travel to a minimum.

 

[Jim B]

I left the 2lb in line for the front disc brakes. The rear disc brakes have no residual valve at this time. As soon as it quits snowing, raining, freezing, I will give it a test.