I have a 77 F600 crew cab with manual hydraulic brakes. I have converted a few cars in the past to power brakes by just adding a brake booster and new dual reservoir master cylinder. Would this work on my F600?

 

Look for one of these on the frame under the driver.

http://www.ebay.com/itm/like/151077357169?lpid=82&chn=ps
Simplified how it works:

http://dave78chieftain.com/Hydrovac/prior-engine-b.gif

That's why your brake master on the firewall looks like it has no power assist.

I am pretty sure you have this system, as this truck would be unstoppable without it. As a pessimist, of course I will be just a pleased to be proven wrong, but take a look, it should be there.

 

All 1973/79 F500/800's came with power brakes. Some had the Midland-Ross P/B booster mounted on the firewall, but...

Most used a Bendix Hydro-Vac which is a remotely mounted P/B booster, usually located on the left outer frame rail.

Here's a pic of one of the Hydro-Vac systems. Booster is basic part number 2005.

 

Thanks guys, I did find the booster. The brakes work okay BUT the pedal is very stiff. It reminds me of a PB vehicle when it is not running and the brakes work BUT take a lot of pressure to apply. The problem for me is I don't know what they should feel like in a heavy duty truck like my F600. Should they feel like a smaller truck with PB with little pressure needed to engage the brakes? I don't hear any vacuum leaks from the booster or lines.

 

Shortly after you turn off the engine, press the brake. When you let off the brake, listen for a slight "wooshing" sound. There is a vent into the cab on some/most/all of these for air to move through. Also, if you press on the brake repeatedly, you will use up the vacuum reserve in a short time, and you will notice the pedal becoming almost rock like.

If you dare and have plenty of runout room, find a slight hill and roll the truck down it with the engine off. Repeat the brake test above. You should go from brakes, brakes, kinda brakes, brakes? BOTH FEET BRAKES to HOLY%$^&*()P.

Another more sane way is to place your foot on the brake as you start the engine after it has been sitting overnight. The pedal should sink a little as the vacuum builds in the booster.

Rebuilt units or rebuild kits are available as these were used on all makes and models of medium trucks for decades.

 

do you have two lines coming out of your master cylinder?

 

Sounds like you might need a new hydrovac unit. Replacement is pretty easy. I did mine yesterday on my 76 F600. Make sure you have good vacuum to your hydrovac unit first. My brakes are as good now as they are on my 2010! Cost like 200 bucks

 

I hate to sound stupid BUT is the hydrovac unit also referred to as the "brake booster"?

 

Yes it is. Under left side of cab. I would replace brake lines and vacuum lines too.

 

See post 2....

 

When I got my truck it had two lines off the master cylinder..Anyone familiar with this arrangement...F600 1977...

 

My truck is a 76 and I believe it to be stock. I have one master cylinder on the firewall with one line coming out. That line runs down to a second "slave cylinder"? Mounted to the back of the vacuum booster and a second line leaves this booster cylinder and goes to the wheel cylinders.