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brake pressure valve centering

I have the brake system apart on my 78' F150. What do I need to do to center the brake pressure valve once I have this system bleed. I'm replacing the Master cylinder, front calipers. rear wheel cylinders, shoes and pads. Blew out the lines to check all fittings and hoses.
 

dustybumpers

don't play well w others
I usually pull the pin out with a pair of needle nose pliers, then put a pair of mini vice grips on the pin behind the head.
Bleed the brakes as normal, then release the vice grips. Works every time for me
 
this valve is mounted to the cross member close to the oil pan. The brake lines connect as well as a wire connector. I think is my brake warning light wires. My repair manual talks about "centering the pressure valve" to reset the warning light. Also I may have my Calipers mixed up left to right. Does the driver side caliper have the brake line connecting to the rear and the bleeder valve toward the front or visa versa?
 

fatherdoug

Tonto Papadapolous
Thanks fatherdoug for the repair manual link. The pictures cleared up a lot for me. I have everything in place. My brakes still feel lousy. They will stop the truck, but I have to push the pedal down too far it seems. The rear shoes are adjusted up close. Every thing is fresh except for the booster. I bought one today. I guess I'll try that and a new vacuum hose for the booster tomorrow. Maybe look close at the master cylinder for air. Even though I bench bleed it and all wheels. Could I still have trapped air? I didn't pull the pin out on the pressure valve? could that be a problem. I have two other vehicles and they both stop on a dime. What am I missing here? :(
 

fatherdoug

Tonto Papadapolous
Might still have some air. Did you start with the right rear? You're supposed to start with the brake farthest away from the master cylinder.

I'm not a brake guru, but I'm assuming that problems with the booster would result in a VERY stiff brake pedal?
 
I'm following instructions to the letter. You make sense. I guess the bad booster would result in a stiff pedal. That I don't have. Just too much travel. Thanks for sticking with me. I appreciate all the advise I get at FTF. :)
 
Ok dustybumpers. How far do I pull the pin. I don't want to break it?
I've never done this before. Maybe that's where my problem is. Simply pull out and clamp to hold with needle nose vise grip and bleed as recommended. Thanks I'll check back here in a bit for your answer. :)
 

Fellro

Moderator
Staff member
Most times the valve re-centers itself once pressure builds back on the opposing side. The valve basically is there to detect an imbalance in pressure. Once the pressure balances, typically (not quite always) they center themselves.

Have you gotten good fluid flow out of each location?
 
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dustybumpers

don't play well w others
Try bleeding first, like Roger said. Usually that's all that's needed. Now if the valve's a little sticky, then you need to do the pin trick.
Not a lot of pull. just pull a tiny bit, just enough to get the mini grip on.
Once you pump the brake pedal, the fluid will push through there, and like Roger stated, then things will center

I guess it's a half attempt at a safety for a broken line, or brake cylinder, the pressure pushes it closed so the fluid can't leak out under pressure.
 

dustybumpers

don't play well w others
There is also an adjustment between the booster and the master cyl. You have to pull the master cyl out of the way, and look in, you will see a bolt heads. You make the rod longer for more pedal, shorter for less. You will spend a lot of time on this one taking the master on and off test driving, it's a very touchy adjustment, and you can make the brakes drag if you go too far
 
I have checked that rod setting and it's correct according to the measurement in the manual. I actually adjusted that and caused the brakes to drag. I went back to the initial setting. Thanks. :)
 
The fluid runs clear and freely each time I've bled the brakes. I don't see air any more using the tube in the bottle of fluid method. It's a mystery to me. I'll be happy to try anything to improve the brakes. It's really a nice truck. Not just because it's mine. It's been very reliable except for a few things like this. I'm retired now and I'm making this my daily driver. Anybody out there got any suggestions jump in here. Thanks all you guys for helping me. As soon I identify the issue I'll post it. :)
 
I think Ben "Utfball68" just did one of the F350 booster upgrades. You might do a search for his thread.


If you get one of the pumps used to pull the brake fluid through from the wheel cylinder, you don't have to mess with the centering pin. Harbor freight has them cheap.
 

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