The Stovebolt Site Forums The Parking Lot Big Bolts Brakes with hydrovac 1.5 ton

This is my first post so please don't bust my chops and make me cry. I'm rebuilding a 46 1.5 ton.I've gone through the engine and 90% finished with the braking system.I recently recieved a rebuilt hydrovac from Jim Carters and they sent me this small white PLASTIC ck valve.My old ck valve is fine except for a couple washer-like parts inside.I would rather use the orig parts if at all possible.Any help out there.THANKS

You must be on the HAMB too... Welcome to the Stovebolt, we're usually pretty friendly around here. Just don't ask any Ford questions!

I'm not an expert on hydrovacs, but I would imagine if the old check valve works worst case is you'd have a spare if the old one ever failed. The question becomes how do you check to ensure the old check valve works properly.

If you check the tech tips here you'll find a couple of articles on these brake systems, and you might find what you need there. It wasn't until I read Jeff Erickson's overhaul tip that I understood how these things even work.

Hydovac Overhaul

If the check valve you're asking about is the one that holds vacuum in the system, you want it to work because otherwise you may have trouble stopping when the engine dies or any other low vacuum situation.

The check valve should be just a brass plug that sits inside of a small housing with 4 machine screws. Take it apart and clean all the gunk out of it. The brass piece should be round with a little 'dork' in the middle pointing up. So long as the seat on it is smooth and the seat in the bottom portion of the housing is smooth it should be fine.

The way this works is the vaccum sucks that little piece up in the air letting vaccum go to the hydrovac. When the vaccum stops, gravity lets it fall down into place giving you a little stored vaccuum for one more easy push on the brakes.

A good way to test your unit is to remove the plug on the back of the Hydrovac and hook up a vaccum gauge. Start the truck and let it run for at least a few seconds. Turn the truck off and it should hold around 17 (+ or - a few) pounds of pressure. If it doesnt hold any or very little you have a vaccum leak somewhere in the system.

Hope that helps!

Good luck, Jeff

Thanks rustednuts for the help on the ck valve. Is there suppose to be a quater size composit disc that sits on the brass piece?The one I have is very fragile looking and I Kinda don't want to Try to remove it.But if I had what I needed to replace it I would.Also where the top section goes together it it looks like there was a thin O ring that sit inside the body section where the two sections come together. The orig. ck valve has to go back in because there is a 3/4"line going from the firewall above the steering colume to about 1/2 way back on the truck.No way to hook-up to it with the new plastic ck valve. Sorry to be so anile about this but this final hook-up to a 2 month total brake re-build.

Im not sure what you mean by a disc sitting on the brass piece. There may have been more then one style used or replaced over the years so maybe???

To answer the second question, I believe there is something to seal the two half of the housing together. Its been awhile since I had mine apart, but there may have been a gasket used.

I do remember digging out a good 3/16" of oil, dirt, grime and whatever out of the valve. Because of the way it was caked on it really looked as if it was a rubber ring of some sort inside, that may be what your seeing. Gas and oil fumes can make their way into the valve via the intake manifold once the engine is shutoff, so over time the valve can get gummed up and stuck.

Im gonna search through my pictures and see if I have any of the assembly.

Jeff

Bota,

Shoot!!! If I'd known, I'd a taken a photo of my check valve yesterday. Just pulled it out, took it apart, cleaned it, put it back.

Yes, there was a o-ring like gasket sitting on the inner ledge of one of the pieces, made of brass I think, that helped seal the unit. Although I "[censored]-punched both halves before dissasembling, both halves were slightly warped in such a way that it would only go back happily the way it was.

The only other part, other than the two halves, 4 screws, and o-ring, is the "stopper" valve itself. Shaped kinda like a kid's spinny top. Rubber face on the side that seals.

After I cleaned it and reassembled, I could test it with my mouth. Sucking one side worked, sucking the other gets nothing, just like it should.

Does this help?

-Michael

BTW,

On my truck, at least, technically, it's a "vacuum assist", NOT a Hydrovac, at least not in the most common usage. Most people, when they say hydrovac, mean the unit as described in the tech tip listed above, which contains brake fluid, and is basically a second, stronger, Master Cylinder.

On my Art Deco 1.5 ton, it's a very simple vacuum cylinder that just helps physically push the master brake cylinder, no other brake fluid involved. I've always liked it, 'cause it doesn't complicate the bleeding procedure!!!

Either way, they use manifold vacuum, and the line is supposed to rise above the level of the manifold, I think so gasoline fumes/condensate don't drain into the vacuum assist/hydrovac and ruin the seals. (I think).

(If I'm right, I'm just showing off. If I'm wrong, I'm just asking for clarification! )

-Michael

Interesting theory about the lines running above the intake. It may hold true for conventinal cab trucks, but the lines could not run above my intake in my COE as there really aint to much room under the floorboards.

Jeff

Ummm . . . that IS a good point . . . hmmm . . .

Are you SURE your brakes really work?

-Michael

I belive I've gotten the ck valve delima solved.I used a rope type gasket, mostly used in plumbing problems to seal the two haves together.We'll see later.I'm now having a problem bleeding the stinking thing.I bought one of those One-person bleeders and just can't seem to get all the air out.Should it take more than one lg container to fill the whole system up?Does the hydrovac hold a lg amount of fluid? I started at the longest line first and worked to the closest(left front).Then bled the 2 bleeders on the hydrovac itself. Still no Pedal!!!!!!!I was told to leave it a day or so and the air bubbles will move to the highest point.I don't know,I'll try anything at this point.

The Hydrovac needs to be bled first. Start with the one closest to the master cylinder in the control body. Then bleed the one at the end of the hydraulic cylinder.

Do the wheels the way you always have.

Then finish with the Hydrovac one more time, same as above.

I know its goofy, but Hydrovac, wheel cylinders, and Hydrovac again should get the job done.

Jeff

Thanks rustednuts,I'll try that tomorrow AM,and let you know how it goes!!!Would you think I need to have the engine running when I bleed the hydrovac or does it matter