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Hi.. good luck with a nos replacement. Sometimes on ebay... but you will pay dearly. After 3 aftermarket failures i plumbed in a valve ftom a 1998 jeep cherokee. Good luck
Brent
And did you push in or pull out the rod for the pressure differential valve when bleeding the fronts?
On the lighter GVW trucks, you pull the rod out, and on the heavier trucks, you push it in. If you don't do this, you'll never get any fluid out of the fronts when trying to bleed them.
So let me clarify. When i first attempted a bleed, i got fluid out of the calipers. I did crawl under today and take a few shots of the main proportioning valve and what the one with the “rod’. Since I am 7500GVW i used a c-clap to push the rod in. While brake pressure was slightly (and I mean slightly) better still very soft. Here are some pics of what I am looking at. Thanks for your assistance
I've never heard of a separate one for the front, but I see that valve rod. Is there one like it on the main valve body, on far end not visible in the pic? I wonder if someone gutted that part of the main valve and then installed the front one to replace that function.
Hey, I just went through and did all of this to my 73 F100 and also put in a new master cylinder and brake booster. I spent days trying to bleed the air out and 3 big bottles of brake fluid. Whenever I thought I had all the air out, I'd find more.
M proportioning valve looks like yours and is inside the driver side frame rail. I don't have the other.
You didn't change your MC, but did it ever run dry when you were changing stuff out and bleeding? If so, you may need to bench bleed it.
Does yours have a power booster? If it is going bad it could make your brakes spongy. Also, if you have one, check that the vacuum line on it is good and going to the right spot.
Are all the bleeder valves good? It could be sucking air in there. If you have a pinhole leak somewhere in your metal lines (could happen when moving things about to change stuff) that could also be sucking in air.
You put the hoses on the front on the correct sides right? They have to be on the correct sides.
I did most of the above and it did help (especially the vacuum line on the PB) but it still didn't feel right. Then I went and got one of those hand vacuum pumps with a gauge and sucked the fluid through twice all the way around starting at the back. I was amazed how much air was still in there. Finally, the brakes were working like they should. If you go this route, put a little grease around the hose where it attaches to the bleeder screws to keep it from sucking outside air into the tube, that way you can see only the air bubbles coming from the brake lines. ((and have a buddy stand over the MC with extra fluid as you will go through it fast))
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