I don't drive my 1996 PSD much. I noticed the brakes seemed soft and found it was low on fluid. I assumed it had a leak. I inspected everything closely and found no leak. Maybe the low fluid was just wear on the brakes and I hadn't checked it. It seems to stop ok, but if I continue to hold pressure the pedal goes to the floor. I replaced the mastercylinder and bled the brakes and same problem. I noticed while bleeding the brakes with the engine off there is a weird noise coming from a valve attached to the power steering pump. It seems to be connected to the booster and I think it's vaccume related. Even if the booster was bad that should just mean I have a hard pedal, not that it would go the floor, right? Any ideals?

 

If the pedal goes to the floor with steady pressure at say, a stoplight that is normal for these trucks. Ford came out with a revised brake booster to resolve it but it not needed unless that sinking pedal really gives you a sinking feeling.

If the booster is bad then yes you would have a rock hard pedal and hardly be able to stop the truck. As far as the valve attached to the PS pump that makes noise I visualize what parts your talking about. The Brake booster and PS system are separate.

 

If your truck has rear drum brakes, make sure that they are adjusted. Out of adjustment drum brakes will give you a low & spongy brake pedal. This will most likely not cure your concern, but it may improve it.

 

Very True! good advise!

 

GubNi It sounds like you have a hydro-boost on your truck. I have never seen one but have read where some have converted over to that system. It would have hydrolic lines running from the pump to the master cyclinder I think. If I remember right the F450 had the hydro boost system.

 

It doesn't have hydroboost.

I read up on a TSB about this problem saying to replace the booster with a special part number unit. I got a new one and will install shortly.

 

New booster didn't help. Here's current status.

I have a 96 F350 4wd diesel. The problem is it has virtually no brakes. With the engine off it has some brakes, but with it running the pedal goes to the floor. It goes about 80% then slowly goes the rest of the way.

I have put on 2 new (not reman) mastercylinders, right front caliper (bleeder broke), new rear shoes, and ebrake cables. Most of the hard lines have been replaced. I have bleed through about 2 gallons of fluid and even bled the porportioning valve. I tried another booster and it didn't help so put the original back on. I also replaced the sensor that plugs into the master cylinder at the end.

At this point I've done everything and have no more ideals.

I have not replaced wheel cylinders (they aren't leaking)

I have not replaced any rubber hoses (they are not dry rotted or swelling up)

I have not replaced the left front caliper

I have found that the right rear backing plate is bent about 3/8" in at one side which might be causing a problem with the shoes seating.

I'm sure something I've done is wrong or it's another problem that I haven't thought of.

 

ABS valve could be the issue at this point.

 

I don't have an ABS valve.

Found the problem. Autozone gave me a MC with 1" ID and the original was 1.25" ID.

 

Unless you have already removed it you do have an ABS valve. Did the correct master cylinder fix it?

 

My problem is fixed, but where would this valve be?

 

Its probably what you called the proportioning valve. Its on the frame rail under the drivers floor board

 

Yep. that it

 

Gubni I was gonna tell ya to check out if you had a 1 1/8" bore MC or a 1 1/4" bore MC. I had the EXACT same problem. I am finding this out more and more of us are having this issue. Someone needs to get this as a sticky or something like that. The '95s and '96s are known for having these problems. And it will drive you nuckin futs trying to fix the problem.

 

The truck has been un driveable since june because of this problem. 4 months - to get the right one I had to tell them I had 130" wheel base instead of 168". I have measured and got about 170".