I just installed a brand new hydro vac into my 56 F750 after a rebuilt one failed in less than 3 years.
I was told at the time of purchase that it would only last for a few years as they use OEM parts that are very old. and newer ones are not being made any more.

I was told by the seller of the brand new one that the probable cause of the failure was gas vapors seeping in to the unit past the check valve thru the vacuum line. He stated that a charcoal filter should be installed into the vacuum line to prevent this.

The new unit cost me about only $445, more than a rebuilt one, but I think that it is worth it.
There is also one available for $395 that probably would have worked, as I never carry the cargo that a F 750 is intended to carry.
New mounting brackets will have to be made and two short brake lines replaced with new ones.

The seller's name is,
Midwest power products
Morris, Illinois
815 942 0550
I purchased it from Rich, who was most helpful and spent the time with me as I asked numerous questions.

 

That's good to know. Is the new unit approximately the same physical size? Did you get a charcoal filter, and how would that plumb in? Do you have a picture?

 

The unit is a little smaller so that you can mount in straight forwards, not slanted like the original.
I placed the charcoal filter in the line that comes from the engine intake manifold to the check valve on the firewall.

The brake lines to the hydrovac are almost the exact thing as the original just a few inches longer.

The charcoal filter is used on GM products in the 70's I think. And should be changed each year.

 

Excellent! Thank you!

 

PS, That nice shiny red paint on the fire wall is the original finish applied in 1956!
The inside of the cab is just as nice with the original upholestery. The tailgate folds down and becomes part of the ramp to load cars into it.
The truck only has 23,000 mi on it. I did instal a more powerful engine in it though along with an auto. trans.

 

Thanks for the pictures. Nice original truck.

What is that valve to the left of the seat next to your fire extinguisher? I know all trucks have a hole at that location but none on the passenger side.My trucks have a rubber plug in the hole.

 

That's a fuel tank selector valve. The truck must have more than one tank.

 

Are you running a single reservoir master? I like the idea of dual boosters and a dual reservoir master, which I have decided to do on my 56 C600. As I remember as a kid the stock system would throw you off the seat in a panic stop!

 

While I was posting Pic's I thought I should a rear view

 

I also thought about a dual master system but since I had rebuilt the entire brake system and all the brake lines are good, I decided that I did not need one.

Be sides, the emergency brake is on the drive shaft, so I have two systems to rely on.

 

Roger could you tell me the part # of the hydrovac? And is it just for the F750? Thanks Garry

 

I believe he called it the 4000 series
Part # 374980N Second series bendix Hydro-vac $445.00 Midwest power products 815 942 0550

It is a later model hydrovac ,9.5" diameter, 17" long that will replace the one in a F750 with a bracket modification.
(I made my own)



There is a smaller one that would probably fit a F600, 7" diameter,15" long, $395.00. I could have used that one as I don't carry the weight that my truck is made for.

I tried it out and it stops fine.