- Joined
- August 1, 2008
- Messages
- 11,624
- Reaction score
- 2,211
- City, State
- MO MO
- Year, Model & Trim Level
- 94 & 95 XLT's
Yes, the HCU is the abs pump unit.
I like the idea of using an F-150 master. Almost did that in the 2nd gen when I was having peddle issues. I was afraid of the booster working or not working, and getting the push rod set right. I settled for a new Ex master. I think the fittings match on the F-150 pump, but I would check to make sure.
So here is what I found (the hard way) out about deleting the ABS pump and adding a Prop valve to compensate. .... The stock prop valve is set for a minimal pressure block. The aftermarket Prop valve must match the stock pressure setting or you will have peddle issues. I installed an adjustable prop valve, so it was a simple matter of turning the knob to lower the pressure. I thought it was the MC, then the booster, then the calipers, and lines. I replaced pretty much everything on the entire system before I learned it was too much pressure to the rear.
Too much rear pressure will cause leakage from one chamber to the other inside the MC, and cause the soft peddle, or a complete bypass and peddle drops to the floor. When this happens, it takes a few seconds for the system pressure to stabilize, and the peddle returns. If there is a weak spot in the push rod plunger seal, the fluids will leak here with too much back pressure. Hard to spot this leak sometimes, as it empties at the booster.
Edit: I am tempted to remove the prop valve and run without. The pressure amount used is very small, and it still worked fine with it as low as it would go. I did a simple test with vice grips, and gently closed the soft lines before the rear calipers. Tested it, and found the soft peddle issue was gone. Removed them, and the soft peddle was back. This is how I learned the pressure was too high. Sounds weird, as you would think there is more pressure by doing this, but it actually just stops use of the rear chamber in the MC. Try it, but use care not to crush the soft lines. Just a little squeeze is needed.
I like the idea of using an F-150 master. Almost did that in the 2nd gen when I was having peddle issues. I was afraid of the booster working or not working, and getting the push rod set right. I settled for a new Ex master. I think the fittings match on the F-150 pump, but I would check to make sure.
So here is what I found (the hard way) out about deleting the ABS pump and adding a Prop valve to compensate. .... The stock prop valve is set for a minimal pressure block. The aftermarket Prop valve must match the stock pressure setting or you will have peddle issues. I installed an adjustable prop valve, so it was a simple matter of turning the knob to lower the pressure. I thought it was the MC, then the booster, then the calipers, and lines. I replaced pretty much everything on the entire system before I learned it was too much pressure to the rear.
Too much rear pressure will cause leakage from one chamber to the other inside the MC, and cause the soft peddle, or a complete bypass and peddle drops to the floor. When this happens, it takes a few seconds for the system pressure to stabilize, and the peddle returns. If there is a weak spot in the push rod plunger seal, the fluids will leak here with too much back pressure. Hard to spot this leak sometimes, as it empties at the booster.
Edit: I am tempted to remove the prop valve and run without. The pressure amount used is very small, and it still worked fine with it as low as it would go. I did a simple test with vice grips, and gently closed the soft lines before the rear calipers. Tested it, and found the soft peddle issue was gone. Removed them, and the soft peddle was back. This is how I learned the pressure was too high. Sounds weird, as you would think there is more pressure by doing this, but it actually just stops use of the rear chamber in the MC. Try it, but use care not to crush the soft lines. Just a little squeeze is needed.
You and your family are in my thoughts tonight.
