Thank you all for the advice!!! I know it sounds like a master cylinder problem and that is why we have changed it so many times but what are the chances of getting 6 bad ones? The other thing is that when the engine is off if the master was bad it would still bleed internally and the pedal would go to the floor even without the vacuum pump running. Our next step I think is to take it to a shop and pressure bleed it. I am going to look into if the master is the big bore one or not that I put on. and as for the RABS valve I'm a bit scared to take it apart because it cost like 200+ from ford and I just put a new one on the other day. I think before I go taking it apart I may use a short section of brake line and plumb the two lines that go to it together and bypass the valve.

 

the '95 I have problems with I plumbed the fluid around the RABS valve and still had the problem?

 

HERE IS THE BLEEDING PROCEDURE, INCLUDING THE ABS VALVE.

NOTE: Bleed primary and secondary hydraulic brake systems separately, bleeding longest line first on each system. Do not allow reservoir to run dry during bleeding operation. Never reuse fluid that has been drained from hydraulic system.

1. Loosen master cylinder to hydraulic line nuts and wrap shop cloths around tubing below fitting to absorb escaping brake fluid.
2. Depress brake pedal slowly forcing air trapped in master cylinder out at fitting.
3. Hold pedal down and tighten fittings, then release brake pedal. NOTE: Releasing brake pedal before fittings are tightened will allow air to enter the master cylinder.
4. Repeat steps 1 through 3 until air ceases to escape at fittings and brake pedal is firm.
5. Bleed brakes as follows: RR, LR, ABS valve, RF, LF

1. Bleed the Rear Antilock Brake System (RABS) valve.
2. Bleed the front brakes using same procedure as for rear brakes.
3. Fill master cylinder to 1/4 inch from top of reservoir or to the proper fill line indicated on the fluid reservoir.
4. Centralize pressure differential control valve, if applicable, as follows:

1. Check brake operation and ensure pedal is firm, road test vehicle.

************************************************** *****

ABS

SPECIAL TOOLS NEEDED

<TABLE cellSpacing=10 cellPadding=1 border=0><TBODY><TR><TD vAlign=top>Description</TD><TD vAlign=top>Tool Number</TD></TR><TR><TD vAlign=top>Antilock Brake Adapter (Bleeder Box)</TD><TD vAlign=top>T90P-50-ALA</TD></TR><TR><TD vAlign=top>Antilock Brake Adapter</TD><TD vAlign=top>T93T-50-ALA</TD></TR></TBODY></TABLE>
(Jumper Cable)

<TABLE cellSpacing=10 cellPadding=1 border=0><TBODY><TR><TD vAlign=top>EEC-IV Breakout Box</TD><TD vAlign=top>T83L-50-EEC-IV</TD></TR></TBODY></TABLE>
CAUTION: Perform this procedure only if the Hydraulic Control Unit (HCU) has been replaced. Follow conventional bleed procedures if the HCU is not being replaced.

1. Perform conventional brake system bleed. See: Brake Bleeding
2. Connect Antilock Brake Adapter T90P-50-ALA (bleeder box) and Antilock Brake Adapter T93T-50-ALA (jumper cable).
3. Press down on the brake pedal (2455) and depress the VALVES button on the bleeder box ( brake pedal will fall).
4. Release the VALVES button and release the brake pedal.
5. Repeat above two steps once more.
6. Depress the MOTOR START button and let the pump motor run for one minute.
7. Perform conventional brake system bleed. See: Brake Bleeding

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<TABLE cellSpacing=10 cellPadding=1 border=0><TBODY><TR><TD vAlign=top>Item </TD><TD vAlign=top>Part Number </TD><TD vAlign=top>Description </TD></TR><TR><TD vAlign=top>1</TD><TD vAlign=top>T90P-50-ALA</TD><TD vAlign=top>Anti-Lock Brake Adapter (Part of
T90P-50-ALA)</TD></TR><TR><TD vAlign=top>2</TD><TD vAlign=top>--</TD><TD vAlign=top>Bleed/Harness Selector (Part of T90P
-50-ALA)</TD></TR><TR><TD vAlign=top>3</TD><TD vAlign=top>--</TD><TD vAlign=top>Green "Motor On" Lamp (Part of T90P
-50-ALA)</TD></TR><TR><TD vAlign=top>4</TD><TD vAlign=top>--</TD><TD vAlign=top>Red "Motor Off" Lamp
(Part of T90P-50-ALA)</TD></TR><TR><TD vAlign=top>5</TD><TD vAlign=top>--</TD><TD vAlign=top>Valve Button
(Part of T90P-50-ALA)</TD></TR><TR><TD vAlign=top>6</TD><TD vAlign=top>--</TD><TD vAlign=top>Abort Button
(Part of T90P-50-ALA)</TD></TR><TR><TD vAlign=top>7</TD><TD vAlign=top>--</TD><TD vAlign=top>Motor Start Button
(Part of T90P-50-ALA)</TD></TR></TBODY></TABLE>

 

I don t know if this part of the abs includes you because I dont know if this is part for the RABS or if it is the RABS.

The ABS valve bleeding came to mind as I have encountered this on other vehicles where I would need a scanner to bleed the abs system. It just popped in my mind now.

 

Thanks for the help. I only have rear abs and the first part of your bleeding description has been done several times. In the second part I thing your reffering to an antilock brake system which I don't have. Remember I also don't have a hydroboost system either just a vac pump. One thing that you did mention was the part about centering the rabs valve with key positons. I didn't know about that and I will have to try that. The only thing is that I would think that after so many starts of the engine and cycling of the key on and off it would have already done the centering part on its own. If it has then the problem still hasn't been fixed. This system is so simple and I feel like a dummy..... I have never been stumped by brakes before. They either work or don't but in this case they kind of work??? if you get my drift.

 

I had a problem with my brake pedal on 1990 F-350 diese DRW, it would have good pedal then, while sitting at a light or stoped for a short period of time, the pedal would slowly go to the floor. I had one mechanic spend a whole day on it and could not figure it out. I took it to a Ford dealer un Arizona while out west and they couldn't figure it out. I took it to Lance Cunningham ford in Knoxville, they replaced the vacuum pump and that fixed the problem on my 1990. It had the best brakes it ever had when I sold it and the new owner, who I know, and he has said nothing about brake problems. If I were you I would replace the vacuum pump and see what happens.

 

That is worth a try 442john.

 

X2 on that!

 

Hello CT you are not the only one with this problem. And welcome to FTE. I too have replaced the pads, shoes, rear drum springs and hardware, rubber lines (all of them), metal lines (rear), rear T block, RABS, vaccuum pump, both calipers, and 5 master cylinders. I was sold the wrong one. I found out I have the big bore master cylinder. However I still have a soft brake pedal. I have gravity bled the truck several times, I have two person bled the truck, I have had a two shops check the truck out and bleed the system. NO luck. Someone on here has got to have the answer. This is the ONLY vehicle that has ever done this to me.

 

Oh yeah and I forgot to mention how many gallons of brake fluid I have gone thru during all of this. I really hope someone has some more info that we are missing. I'm going back out today to figure this truck out.