67 m715 brake pedal to the floor

Okay guys, I am having an issue with my 67 m715 kaiser. The brake pedal goes all the way to the floor. It has been sitting for a couple years as I bought a new place and haven't had time to drive it. Anyway I checked the fluid level and it was dry so I filled it up with fluid and I have pumped and pumped and pumped the pedal and still no pressure at all and the fluid hasn't gone down. Any suggestions? It is all bone stock the truck.

Any help is greatly appreciated. Want to get it up and driving again :)

Did you open the bleeders in the wheel cylinders?

No I didn't, I figured pumping it before opening them up would still build up some pressure?

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Originally Posted by racingjoe66

No I didn't, I figured pumping it before opening them up would still build up some pressure?

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You may have too much air in the system for that to work.

If your master cylinder drained, the leak must be quite apparent, so you know what to fix.

You need to open the cylinders and bleed the brakes to get the air. There must be too much air in the system.

Your master cylinder piston might be stuck due to corrosion in the bore. That's what I found on my truck when I bought it and it had been sitting for 5 years.

I was going to guess that the seals in the MC shrunk/dried out while sitting and the fluid drained out onto the inside of your firewall.

But when that has happened to me refilling the MC and pumping it up worked... because the leak is at the top of the system. Must be leaking further down stream.

You have any fluid leaking down the inside of any of your tires? Maybe a wheel cylinder seal let go. Or one of the rubber hoses.

If it's been parked on grass or dirt it's probably impossible to tell where it's leaking ... and if it leaked out a while back and dried up... But now with fresh fluid in it to leak out it might be easier to track down.

I did notice after I filled it up and was pushing the pedal by hand to pump it that there was a drip from the bottom of the master cylinder where it comes through the firewall on the inside of the truck. Is there a way to replace the seal or best to buy a new MC?

And yes it was parked in the grass and I didn't see any other places that looked like they leaked at all.

At the risk of raining on your parade, I think you may have to rebuild the master cylinder and the four wheel cylinders. No doubt, from sitting, you have a mess in all of them and if rusty (probably), they won't rebuild without leaking.

Yes, lots of work but one thing at a time and you are good to go.

Sorry if I offended; it was unintentional...

I hate to sound like a 'Safety-Nazi', but.....
For the safety of yourself and others, you really should rebuild, or replace all four wheel cylinders, and the master cylinder if this vehicle is driven on the road.
The stock single circuit fluid system has no fail-safe if any part of the system loses pressure.

At least make sure the parking/emergency brake is working.

This is an excellent time for putting a double circuit master cylinder.

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Originally Posted by gerrykan

I hate to sound like a 'Safety-Nazi', but.....

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LOL, I guess somebody's gotta do it...

I started to suggest that the whole system is due for upgrades myself, but it sounds like it isn't driven.. and I know how that budget thing goes. Having to replace the whole system on mine piece at a time.

Hey, guys, been awhile, tooooo long! I'm bringing my M715 back to life and ran into the same thing, brake pedal to the floor. Over the years I've had to replenish the brake fluid every once in awhile, but now it's a pretty good leak. I noticed the paint on my firewall/floorboard blistering pretty badly, points to a hosed master cylinder. I'm not going to deal with a rebuild, either stock or dual-circuit. A bit late in the day now, I'll search tomorrow... Later.

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Originally Posted by bump_r

I noticed the paint on my firewall/floorboard blistering pretty badly, points to a hosed master cylinder.

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So common. Dumps the fluid on the floor and blisters the paint. If a slow leak, it evaporates so you keep looking for where it is leaking.

The truck's had a phantom leak for some time, M/C goes dry when sitting for lenghts of time, never found trails down tire sidewalls, backing plates, or puddles on the ground. I've already upgraded all 4 slaves with Ford items, had good, solid pedal when used, so I'm pretty confident the M/C pushrod is THE culprit, just never spent enough time "down under" to see the telltale signs. I've got the dual-circuit Cardone on the way. I am a bit concerned, the pic on Amazon appears to be the disc/drum variety as the front and rear chambers are different sizes. I hope it's just a "stick photo" and it's REALLY a same volume/pressure front versus rear that I need for a drum/drum setup. It came from Iowa, should have had jeepistdoug checked it.

The outputs on the cardone 10-1371 which is disc/disc are 9/16 for front and 1/2 for the rear. get reducers for your line size. also the stock block for the brake lines should be replaced with a proportioning valve from wildwood and is adjustable for rear output. I just did this on my truck and am dealing with a 49 yr old brake line that decided to leak when I tried to move it. and doesn`t want to come off front brake hose.

Poop, I got the 10-1331 coming.

the 10-1331 has a bigger piston 1 1/8 same size outputs. it will work. so don`t fret.

But it is a disc/disc or drum/drum? Same pressure & volume from each output?

I believe its disc/disc its got the same outputs as 10-1371. you may need a proportioning valve as the stock brake lines come off a brass block attached to the frame. the wildwood proportioning valve has a handle that adjusts the pressure to the rear brakes. you can decrease press to rear by turning handle if your rear brakes are locking up. more press to front brakes is normal as that's where the stopping power mostly comes from.

the brake block I took off had a 1/4" line coming off of m/c to the top of the block. the rear brakes come off the rear of the block mine was 3/16". the front brake lines come off the front and bottom of the block they were also 3/16".

the reducers screw directly in to the m/c ports and you will need to size them accordingly.

a 3/16" LINE has a 3/8" thread and 3/8" wrench size. a 1/4" LINE has a 7/16" and so on.