Question brake problems

[Gubni]

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?

 

[BJS]

Are you noticing the pedal drop to the floor when you have the engine running or not?

I'm thinking you are confusing the vacuum pump (just above the PS pump) with the power steering pump and if you are pumping or bleeding the brakes then noise from there would not be unheard of.

There is a TSB for a zero loss brake booster which solves a sinking pedal when sitting for periods with your foot on the brake.

 

[Gubni]

I notice it more with the engine running, but it also does it when it's not.

probably right on the noise.

I'll try to do a search for that TSB - thanks.

BTW - feel free to link me.

 

[Patrick Feeley]

When my original booster failed, the pedal would almost be "sucked" to the floor when applying the brakes. I never did have the low, creeping pedal that gets mentioned, but maybe I just was used to the truck. I did put in the zero-loss booster which solved my problem. The following is from the Dieselmann's site:

"1997 and earlier diesel trucks equiped with vacuum power brakes--Low/creeping pedal:
Many owners have complained of a low or creeping brake pedal on their trucks, often mistaken for a bad master cylinder or Rear ABS valve. If the condition occurs after the vehicle has come to a stop, and no other brake concerns are found, (worn or out-of-adjusted brakes, cocked pads, or hydraulic problems) the condition is normal and the result of the vacuum pump replenishing the vacuum inside the power booster. Ford has developed a Zero-Loss Travel brake booster to correct this condition if the customer finds it unacceptable. This part is only for use on diesel-equiped trucks--P/N F5TZ-2005-CA--and is not a service replacement; it must be ordered by the part number, not vehicle application."

Cheers!

 

[Gubni]

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.

 

[Gubni]

Found the problem. Autozone gave me a 1" ID mastercylinder and my original was 1.25" Works now!

 

[DaveBen]

Now you know why I NEVER go to Auto Zone... They are worse than Kragens!!

Dave