Brake pressure differential valve

Suspension, steering, brakes, wheels & tires

Moderator: FORDification

Post Reply
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Brake pressure differential valve

Post by 69f-100 »

I'm doing a complete brake system overhaul to my 69 100 2wd with 4 wheel drum brakes. I'm not 100% sure if this is what it's called, but can and does this valve need to be rubuilt? If so where might I find the parts to do so?
Image
Last edited by 69f-100 on Mon May 30, 2016 8:29 am, edited 1 time in total.
User avatar
Ranchero50
Moderator
Moderator
Posts: 5799
Joined: Wed Nov 08, 2006 7:02 pm
Location: Maryland, Hagerstown
Contact:

Re: Pressure differential valve

Post by Ranchero50 »

You can take it apart and make sure the slug in the middle moves so it'll make the lamp light up when one circuit loses pressure.
'70 F-350 CS Cummins 6BT 10klb truck 64k mile Bahama Blue

Contact me for CNC Dome Lamp Bezels and Ash Tray pulls.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

Ranchero50 wrote:You can take it apart and make sure the slug in the middle moves so it'll make the lamp light up when one circuit loses pressure.
Ok, I'll check it out. If it doesn't, do they have replacements?
ultraranger
Blue Oval Guru
Blue Oval Guru
Posts: 1147
Joined: Wed Apr 27, 2011 9:15 pm
Location: Arkansas, Camden

Re: Pressure differential valve

Post by ultraranger »

The valve you have pictured is a pressure differential valve.

Rebuild seals are available from Muscle Car Research.com (see following link).

https://musclecarresearch.com/valve-kit-whead1


Image

Image
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

Any idea how to get it out? It appears to be froze in there. I have it soaking in pb blaster right now.
ultraranger
Blue Oval Guru
Blue Oval Guru
Posts: 1147
Joined: Wed Apr 27, 2011 9:15 pm
Location: Arkansas, Camden

Re: Pressure differential valve

Post by ultraranger »

69f-100 wrote:Any idea how to get it out? It appears to be froze in there. I have it soaking in pb blaster right now.
Probably a big mistake. PB Blaster is a petroleum based product. It will make the seals swell, causing them to grip the differential valve spool even tighter.

Brake system seals aren't compatible with petroleum based products because brake fluid (DOT 3, 4 and 5.1) are synthetic based fluids --not petroleum based.

At the bottom of the link I provided, it gives a teardown/rebuild procedure on that valve. Listed in blue letters that says: ("Complete rebuild instructions.")

If you get the valve internals out, you need to make sure you get all the penetrant oil residue out/off of the valve, so that it doesn't contaminate the new seals and ruin them.
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

I sprayed it all off with brake clean, just got to find something to soak it in.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

ultraranger wrote:
69f-100 wrote:Any idea how to get it out? It appears to be froze in there. I have it soaking in pb blaster right now.
Probably a big mistake. PB Blaster is a petroleum based product. It will make the seals swell, causing them to grip the differential valve spool even tighter.

Brake system seals aren't compatible with petroleum based products because brake fluid (DOT 3, 4 and 5.1) are synthetic based fluids --not petroleum based.

At the bottom of the link I provided, it gives a teardown/rebuild procedure on that valve. Listed in blue letters that says: ("Complete rebuild instructions.")

If you get the valve internals out, you need to make sure you get all the penetrant oil residue out/off of the valve, so that it doesn't contaminate the new seals and ruin them.
What do you recommend as a penetrant oil?
User avatar
sargentrs
100% FORDified!
100% FORDified!
Posts: 9866
Joined: Fri Jun 22, 2007 9:30 am
Location: Georgia, Jasper

Re: Pressure differential valve

Post by sargentrs »

How about acetone and synthetic automatic transmission fluid? A while back somebody posted a very scientific experiment to determine the best rust busting compound between 6 different products and compounds like PB, WD40, Kroil, etc. A 50/50 mixture of acetone and ATF beat them all in something like a 2" bolt/but rusted together broke loose with 500# torque or something crazy high like that. Synthetic ATF is non petroleum based so may be compatible. Just a thought.
Randy
1970 F100 Sport Custom Limited LWB, 302cid, 3 on the tree. NO A/C, NO P/S, NO P/B. Currently in 1000 pcs while rebuilding. Project thread: http://www.fordification.com/forum/view ... 22&t=59995 Plan: 351w, C4, LSD, pwr front disc, p/s, a/c, bucket seats, new interior and paint.
1987 F-150 XLT Lariat, 5.0/C6 auto.
66f250cs
New Member
New Member
Posts: 64
Joined: Thu Feb 26, 2015 1:09 pm
Location: Preston, ID

Re: Pressure differential valve

Post by 66f250cs »

To remove piston, remove yellow plug on the end and apply air pressure to the port with the light blue plug. The other ports might have to be plugged with screw in plugs. If air doesn't do it, I made up a plug with a zerk and used my grease gun to push out the piston. You will have to get all of the grease out of the body and ports. That takes the most time. I also installed new o rings on the piston and wetted it with brake fluid before insertion into the main body. If you mark the waist with a Sharpie and peer through the center port you can have the piston centered before you install it. Get or make the "piston position hold screw" and insert into the switch port to hold position of the piston. Install the rebuilt valve and brake lines except the switch. Bleed brakes and road test. Finally, reinstall the switch. The brake light on dash should only light on startup but stay out during drive mode.
66 F250 camper special
69 F250 Explorer
85 Mustang GT with 1900 original miles
92 Festiva with 538,000 original miles
86 E350 extended WB van
Various IH & JD tractors (5)
TT & XT500 mc's (6)
BSA, Triumph's and twenty Yamaha two strokes
User avatar
Ranchero50
Moderator
Moderator
Posts: 5799
Joined: Wed Nov 08, 2006 7:02 pm
Location: Maryland, Hagerstown
Contact:

Re: Pressure differential valve

Post by Ranchero50 »

I had to clamp mine in the vice with the far end against something solid and drive the plug free with a brass punch. Need to be gentle and not bugger it up but also shock it hard enough for it to move. Once it broke the corrosion grip it came out pretty easily. Gave it a swipe with a Scotchbrite pad and it went back in smoothly.

100 psi of air has about 20 lbs of force on a piston that small. Shocking it with a 2lb hammer will generate 200 or so. I was never much good at math but understand the practical application well enough.
'70 F-350 CS Cummins 6BT 10klb truck 64k mile Bahama Blue

Contact me for CNC Dome Lamp Bezels and Ash Tray pulls.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

I sure hope I can get it out, it's really stuck in there. I just can't get a pair of needle nose pliars in there to grab a hold of it. Not sure if I have a brass punch that small or not. I'm going to work on it again this weekend.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

I just cannot get this piston out of this valve. It is really stuck in there. I've got it soaking in acetone, hoping it will help.
ultraranger
Blue Oval Guru
Blue Oval Guru
Posts: 1147
Joined: Wed Apr 27, 2011 9:15 pm
Location: Arkansas, Camden

Re: Pressure differential valve

Post by ultraranger »

There are numerous synthetic penetrant oils on the market. This is just one such example.

https://m.grainger.com/mobile/product/L ... tic-29FX97
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.
User avatar
69f-100
Preferred User
Preferred User
Posts: 427
Joined: Wed Sep 22, 2010 12:21 pm
Location: Ohio, Montpelier

Re: Pressure differential valve

Post by 69f-100 »

I'm going to have to try and find one, it just will not come out. I posted in the "parts wanted" section, hopefully someone has one.
Post Reply