1993 F-350 Brake Issues

Your brake peddle should not go to the floor.

Sounds like you may need both a new master cylinder and a new booster.

Disconnect and plug the booster vacuum source and see what happens.

DO NOT drive the beast till the brakes work properly.

Well I get fluid to all my brakes that's y I think it's the booster

Are the rear drum brakes PROPERLY adjusted?

Yes the brakes are properly adjusted

Then by all means replace the booster.

What does your copy of the Haynes/Chilton have to say about the issue?

I do not have a copy of the manual

The booster just increases the force on the master cylinder. Remove the resivior cap from the master cylinder have someone press the brake pedal down. There should be little to no movement of the fluid as the petals depressed. If fluid is rolling to the surface seals on the spool in the master cylinder are bad. What you hear could be just the excessive amount of air that the booster taking in due to how far the petal being depressed and how quickly.

This is not to say that there might be a problem with the brake booster.

Have a professional check them out!

By rolling to the surface do u mean coming out where the cap is with it off? What if there's brake fluid between the booster and firewall?

You're not supposed to tell us there's brake fluid leaking between the booster and firewall until we ask. We will eventually guess all of the symptoms.

That's how 20 questions is played.

Now, to speed things up, what other symptoms (no matter how insignificant they might seem) are associated with this issue?

Brake pedal goes to the floor, fluid between booster and the firewall, no leaks from calipers or drums I bled the proportioning valve, pedal still the same goes to floor unless the trucks not running also it has a hissing sound when I press the brake down unless its not running

Will application of brake effort on the pedal slow the motion of the truck? Is it enough to stop the truck? Does the emergency brake operate correctly?

Did the symptom of mushy pedal develop slowly (weeks) or overnight? Did you get new tires recently... front end alignment... brake pads or rotors... new stereo or seat covers?

Does the truck live a happy empty life, or is the box full of rocks or construction debris most of the time? How about towing trailers?

It only stops with the front brakes but stops very slowly. The truck has been this way since I bought it. It is a wrecker (tow truck). I put new pads on the front but the front work like they should

It only stops with the front brakes but stops very slowly. The truck has been this way since I bought it.
The truck has been this way since I bought it.???????????????????????????????
You are a danger to society!

It hasn't been drive except when I brought it home

I had a Ford E 350 and braking was tricky in stock form. Loaded it was fine but empty it would change ends very quickly if not careful as back brakes were too strong. I installed a variable Proportional valve from a racing catalogue under the dash within easy reach. Then I did some testing and determined the best empty and best loaded position and marked the handle. This way I was able to have straight line braking with a simple turn of the Proportional valve. As for your brake issues is sounds like a trip to the salvage yard for a booster and I would suggest a quality rebuild master cylinder. Brakes are not to be fooled with, far too important for you and especially me.

Now wait a minute, you bought a tow truck for towing cars right. Now in my mind thats says you might need to know something about working on them. But, from your post here that is one area that you might have missed out on a little bit of training. Brake repairs are some of the easiest things to do. They are simple to trouble shoot and then repair, especially on a vintage 93 model. I hope that you take this to someone who knows what they are doing. to get it fixed before you proceed down the road again.

The emergency brake works correctly

The master cylinder and booster are bad. Replace both.

Been there done that.

I would suggest you go to a parts store and purchase a rebuild master cylinder and brake booster. Fluid between the fire wall and booster indicates a bad master cylinder. Hissing sound suggests a bad booster.

That just keeps the firewall from squeaking.

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Ya I highly dought that

'what if there's brake fluid...' sounds like your master cylinder is leaking...if you're not a mechanic, get a mechanic to rebuild or replace it...

I can do it myself already have it off

Yes with cap off do you see a lot of motion in the fluid as the brake petals depressed.

If there is brake fluid where the booster is attached to the fire wall. Is a sign that the diaphragm in the booster is bad. Not only that the master cylinder is leaking. Fluid is leaking from the seal of the master cylinder. Into and through the diaphragm of the booster. If the seal on the spool at the end of the master cylinder is leaking. Then most likely the other seals on the spool are in poor shape.

It seems to be a frequent problem....here's a fix I found...

"go to Ford and order it by this specific # F5TZ-2005-CA It's called a zero loss booster. I paid $141 for it."

I don't know if this is the specific one for you, so double check for fitment if you do go this route.....

Im in the master cylinder camp

Check out some of the many Ford Forums on the web.

(General note to the forum) I went to two Ford forums and was appalled at the language and rudeness there. CR4 is so much more well mannered (even when I go on a rant) than most open forums I've seen.

Sounds to me as if you need both the booster AND the master cylinder. BTW, from sad experience, fill the new master cylinder and pump the air out of it before you install it. This will save lots of time and brake fluid.

Lots of master cylinders come with a "bench bleeding" kit.

What may be confusing you is that master cylinders have been dual for a long time. So, the front can leak and the rears not.

The key here is the fluid at the firewall and the fact that only front or back work.

The boosters generally develop vacuum leaks which cause rough idle and higher pedal effort.

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Having a single master cylinder isn't fun, I had a brake spring brake on a 1965 vehicle and whoops, no brakes. Drove home using the emergency brake. About 7 miles.

Then on a 1968 vehicle, one of the dual cylinders had a leak. During high speed stops, the pedal went nearly to the floor.

One test, is to put constant pressure on the pedal with the emergency brake off. Engine off. pedal should be firm.

"pumping" the brakes is usually a sign of air, since air is compressible.

I havn't seen brake problems in years.

Inside your brake booster there is a rubber diaphram which has a hole in it this is the hiss that you are hearing which is the loss of vacum boost resulting in pedal movement to the floor . Note if you turn the motor off with the brake pedal depressed and start up with said pedal still depressed there will be a slight pedal lowering felt but only slight not fully to the floor if the system is operating correctly.

If the rubbers are perished in the master /slave actions, fluid loss is the result,the hiss denotes vacume problems,disconnect the tube connected to the manifold then apply the brake if there is no hiss check vacume rubbers.