The Stovebolt Site Forums The Parking Lot Big Bolts Hydrovac brake question

I recently acquired a '50 4100 cab and chassis that has very low original miles on it. However it has been sitting up for the better part of 40 years. Needless to say the brake system was fossilized on it. It is equipped with a hydrovac unit that is also currently in a fossilized state. I am in the process of restoring the brakes and to my delight I have discovered so far that I haven't really had to buy many parts. New rubber lines and a few new cups, etc, but everything else is in good, restorable condition. My question is this - were ALL of these size trucks equipped with the hydrovac setup or was that an option? I don't have any plans to haul any 30,000lb log trailers behind this truck. More than likely I'll be running it up and down the road here locally, empty. Maybe to a car show or two or a parade, etc. Can I get by with just deleting the hydrovac unit and plumbing directly to the main master cylinder? The truck has a 1.25" master cylinder with 1.25" wheel cylinders on all four corners. The rear brakes are 15" x 3" and the fronts are 14" x 2".

Either way I'm going to try it. I am just wondering mainly if anyone else has done this and what their opinion of how well the brakes work without vacuum assist was.

The hydrovac would have been an option. As long as the bed and/or load is not too heavy it should be OK. If you reline or replace the brake shoes, be sure to have a brake shop "arc" the shoes to each individual drum. If you don't the brakes will not work well until the shoes have worn to the drum and you have full contact.
1950 was the last year of the Huck brake system. With the single master cylinder and periodic requirement to adjust the shoes, many people, especially daily drivers, don't care for them. Three of my trucks have this type brake and they function just fine for recreational driving and light loads. Also, remember the steel lines rust from the inside out, so ideally you should think about replacing those.
Kent

I just went through the brakes on my 58 2-ton and replaced all the steel lines. Most looked just fine from the outside but, when I was bending them to put them in my garbage can, you could tell by the way they bent that they were pretty thin in some spots. For the 25$ I spent on a roll of brake tubing and fittings, it was well worth it! Interesting thought of bypassing the hydrovac unit!

You might want to consider a reman hydrovac. I last went looking for one about 10 years ago but they may still be available. I think I paid about $175 for it.I have seen kits for them advertised recently but I don't remember where.

Looking at the spec sheets, the hydrovac provides 63% of the braking force at 1,000 psi. I put a hydrovac on my 1-ton and have been very glad I did. Before, more than once I had both feet on the brake pedal. On the upside, I ran over 100,000 miles between brake jobs. Now they wear faster.

I would not want to be in the position of trying to explain why I disabled part of a brake system to some ambulance-chasing lawyer after an accident, no matter whose fault it was, particularly if injuries were involved. Ditto on replacing the steel lines!
Jerry

I echo HRL and others, the added 900-1000 psi of brake line stopping force is very handy to have. With out it you will be driving a BIG truck with poor brakes by today's standards.

Mike B

Thanks for all the input fellas.

There have been other posts in this forum regarding hydrovacs and where to get new ones and where to get then rebuilt, etc. Search around here a bit and you should find out anything you need to know.

There are several on eBay, don't know all applications, though.

I just stumbled on a great catalogue(online) with applications, installation, bleeding instructions, almost 200 pages, go through it and just print out the applicable sections.

'Precisionrebuilders.com'
800-325-2690, Kim(gentleman) knows what his talking about.

I don't know how original you want to be, but with the installation of a power steering(hydraulic) pump, you could install a hydroboost system, much less room required, will replace the hydrovac unit.

Ed

Just thought I'd post some followup to my original post - I finally got this thing on the road with the brakes plumbed directly to the master cylinder, bypassing the hydrovac. It has PLENTY of brakes and stops just fine. In case anyone was curious.

I probably should not admit it since, obviously, opinions seem to be pretty strong that we should all have a functioning hydrovac, but I'm driving my truck without one. I didn't take it off but somebody else must have sometime between 53 and 4-5 years ago when I got it. Truck stops just fine as long as you drive like you know it's 63 year old technology and iffy at best. Start slow. Drive slow. Downshift and brake in advance. Enjoy.

Geo

I hooked up a bypass brake line in my 630 while working on my hydrovac, with a load, must push very hard to get results, be very careful.

Ed

The Hydrovac adds about 900 pounds of additional line pressure. You'll wish you had it the first time you panic stop doing 50 mph when a little car cuts you off.

Mike B

Ok you guys have convinced me. I need a hydro-vac. I can get one built here in Phoenix if I can find a core. Anybody have a build able core they're willing to let go? Thx.

Geo

Place a part wanted ad in the Swap Meet.

Your truck must be geared significantly higher than mine. About 35 mph is top cruising speed in mine. It'll do 50...wide-[censored]-opened, but that's about it.

I got a hydrovac for my 59 from the local orielly auto parts. I did trade my core to get a little better price. How different are they for your truck. I can look back at the receipt to get the part number if that would help.

Edit... I found it online:
BrakeBest Brakes - Brake Booster
Line: BHH | Part # 51-8028

Thanks for the input Gene, I am not really searching for a replacement at this point. I have my brakes hooked up and working just fine without it. I have no need for the additional braking power for this truck. I do not intend to haul heavy loads with it. It stops just fine without it. In fact - I can lock the wheels up on it without any trouble.