'76 F-250, cannot bleed rear brakes

[szilagyic]

Hello:

I have a 1976 F-250 that had been sitting for a couple years, and I recently got it running again. Immediately I discovered two brake problems. There was a leak with the front driver's side line, and the rear passenger's side brake cylinder was also leaking (fluid coming from within the drum). So, I replaced the front driver's side line and bled it, everything was fine there. I replaced the rear cylinder and also replaced both rear lines from the Y connector to each side, because they were in rough shape. Now, I cannot get the rear brakes to bleed. I've tried manually bleeding with somebody pushing on the pedal without the engine running, but nothing comes out of the bleeder screw on either side. I also started the truck and pressed the brake and still nothing.

Can anybody offer any suggestion as to how to get this to bleed the rear brakes? Thanks in advance!

 

[blacksnapon]

Hello:

I have a 1976 F-250 that had been sitting for a couple years, and I recently got it running again. Immediately I discovered two brake problems. There was a leak with the front driver's side line, and the rear passenger's side brake cylinder was also leaking (fluid coming from within the drum). So, I replaced the front driver's side line and bled it, everything was fine there. I replaced the rear cylinder and also replaced both rear lines from the Y connector to each side, because they were in rough shape. Now, I cannot get the rear brakes to bleed. I've tried manually bleeding with somebody pushing on the pedal without the engine running, but nothing comes out of the bleeder screw on either side. I also started the truck and pressed the brake and still nothing.

Can anybody offer any suggestion as to how to get this to bleed the rear brakes? Thanks in advance!

Possibility of a bad master cylinder because of the extended non use.

 

[Mil1ion]

I say it is more than likely a rusted up Proportioning valve.

You need to evacuate all the brake fluid in the system and make the complete brake system secure.

 

[mrfixit]

Yep, most of those components are cast, and are as such porous. Sitting for extended periods just lets it soak up moisture in the system, and corroding/rusting away. Fortunately most of those things are not that expensive. Might also take a hardy look at the brake springs as well. If they are rather rusty, they could be headed for a fail, too... and that gets expensive left unattended.

 

[szilagyic]

Thank you for all of the feedback. Today I took a closer look and it appears that no fluid is coming out of the pressure differential valve (I'm assuming that is the same as the proportioning valve?) that runs to the rear brakes. I made sure that I pulled the bleeder rod out on the pressure differential valve, but that did not help. But, I noticed that when somebody presses on the brake (truck not running), that the bleeder rod pops out. Is that supposed to happen? Can this valve be "reset" or is it pretty much shot? Just checking one last time before I go ahead and replace it. Thank you!!

 

[brownfoot]

I seem to remember that I had to hold the rod in to bleed the rear brakes
it's been several years since I replaced everything, except the porportioning valve, including lines, wheel cylinders, ebrake cables, hardware, etc.
If I remember correctly whatever position it was in was opposite from what my manual said, either hold in to bleed or pull out to bleed.
anyway, doing the opposite allowed me to bleed the brakes

when you push the pedal and it comes out, does the brake light on the dash come on?
and also there is no fluid comming out to feed the rear brakes?
try to hold the rod in and have someone push the pedal......slowly...with the rear line disconnected, you should get fluid out the port
if you don't, then there is a blockage in the valve and you may need a new one...........replacements are available, but pricey

 

[Mil1ion]

The bleeder rod is PUSHED IN to bleed the FRONT Disc brakes.


IMG]http://i69.photobucket.com/albums/i75/mil1ion/67-79%20Ford%20Truck%20Information/Brake%20Related%20%20Info/Brakebleedingwithrod.jpg[/IMG]

Tough to find an NOS PPV, The ones available now are adjustable.

Some guys try to restore the old PPV

 

[gsxr1238]

According to that procedure above,it depends on the GVW of the truck as to which direction the bleeder rod is held.That determination needs to be made in order to correctly position the rod to allow flow to the rear lines.

 

[Mil1ion]

Didn't realize this didn't show up on previous post

 

[szilagyic]

OK I went out and took a look at this again. The brake light is NOT coming on at all, when we press the brake or not.

I did try clamping the bleeder rod IN just to see, and no luck, no fluid is coming out of the valve to the rear line. Also the pedal hardly travels at all, if that makes any difference here. In fact even when the truck is running, the pedal doesn't travel very much but that's the way it's been since I've had this truck (about 10 years). My valve is exactly the same as the pic from Mil1ion.

I think the valve must be the problem here. It is strange that when I first got the truck running, somehow fluid was coming out of the left rear brake cylinder because it started leaking right away, yet now I cannot get any to come out. Thanks again to all and to Mil1ion for posting that info.

Started looking around and you guys are right, these valves are hard to find. The dealership said they can't look up any parts older than 1980. But I noticed that the valve is exactly the same on my '86 F-150 so I'm going to have them look that one up.

I'll be sure to post back the results. Thank you all!

--
Chris

 

[szilagyic]

OK, well I got a replacement valve (used) from a salvage yard. But, I'm having the exact same problem! Here's the current status:

I hooked up the replacement valve to the old lines, and immediately had somebody press on the brakes and fluid came out from both lines from the master cylinder. Then I tightened the lines. But, I'm having the same problem as before. No fluid is coming out of the proportioning valve to the rear line. I don't get it. Is it possible that the master cylinder is the problem? That's the only thing I have not replaced yet. I didn't think it was the master cylinder as fluid comes out of it for the rear line to the valve, but no fluid seems to be making it through the proportioning valve. Any help would be greatly appreciated. Thank you!!!

 

[szilagyic]

OK, finally got the problem solved. I ended up finding a new valve on Ebay, and sure enough it works fine. All inlets/outlets on the valve work now. Got the brakes bled and all is well. Only took about 6 pumps and fluid came out of the rear cylinder(s).

Just for the record, before I installed the new valve I was able to take my air compressor and blow air through the front/rear inlets, and air came out of the outlets. I also never messed with the bleeder pin that everybody has been talking about, I bled both the front/rear without using the bleeder pin.

Thanks for all of the help!