The Stovebolt Site Forums The Parking Lot Big Bolts Hydrovac

I know this topic has been beat to death here, but my '59 Viking 40 has been having some brake problems. I had suspected, and my mechanic has now confirmed, that there are some issues with the hydrovac. I know people on here have either gotten theirs rebuilt, or gotten new ones, but so far my guy has not been able to locate one through any of his suppliers. But a couple questions did come up and I thought I'd ask here.

1. Does the 40 series (1- 1/2 ton) take a different unit than the 60 series (2 ton)? I had assumed they were the same. He's being told they are not.

2. They also asked him whether the truck had a V-8 or a 6 cylinder--does that make a difference? This truck has a V-8, but my understanding is that it was added later, and is not original to the truck.

The plan for now is that they are going to bypass the hydrovac (and possibly remove it) for the time being so we can at least drive the truck for now. Just wondering if this would work for a permanent solution. This truck is not going to be hauling any heavy loads--at least not while I own it--and not many farmers are going to be looking for a 63 year old grain hauler! Otherwise, it will at least give me the rest of the winter to look for a rebuild or a replacement. The truck itself will not be driven over the winter.

Thoughts?

Hi Rich, I rebuilt my entire brake system except the Hydro-Vac, that was a couple years ago. I bypassed the Hydro-Vac by not connecting the brake lines to it, I drove the truck with manual brakes for that time even with some loads. You have to anticipate any trouble ahead as the brakes are not fast acting BUT they still bring the truck to a stop. I recently ordered a rebuild kit for the Hydro-Vac and that project was successful, now the complete brake system is in great shape and I don't think twice about it. My truck is a 2 ton LCF with the factory 283 V8.

Geoffrey Rosenberg at Alretta Truck Parts in Massachusetts (508) 788-9409 has tons of brake part knowledge. I bought all my brake parts from him including my remanufactured hydrovac from him a few years ago.

There should be a tag on the Hydrovac unit with the Bendix part number, what's the number?

My parts books show that the 55-59 Series 4, 5 & 6 (exc. HD Brake Booster) used the same Hydrovac.

See if there's something in this thread that helps...

https://www.stovebolt.com/ubbthread...895/bendix-or-midland-brake-booster.html

Mike B

Rich's Toys Service your hydro-vac like the service book says,Jim Carter himself told me to use hydraulic jack oil from my local FLAPS in it. Fixed it right up,have 2 that are 73 yrs old work fine. That leather cup in there gets dry,needs lube.

If you cant rebuild it yourself, i got mine rebuilt by cardone through rock auto for about $170. Only place i could find that would rebuild it.

When I rebuilt mine I used motorcycle hydraulic fork oil for the leather.

78 buckshot Most oil would be a big no-no around brakes,I filled an 1-1/2 wheel cylinder cup with hydraulic jack oil to see,never hurt it at all. My OLD hydraulic jack guy said use ATF in em !! (the jacks) So go figure,my hydrovacs have had HJO 3 or 4 times their happy.

If everything in the Hydro-Vac is correct, the few ounces of oil in the air chamber shouldn't come in contact with the brake fluid section. I think I contacted the company that supplied my kit and checked with them.

78buckshot Not scared of the hydraulic jack oil anymore,try to put it in twice a year. Boosters are happy will slide the tires,usually climb on the brakes at my road to see if they are working right. Full pedal stops good !

My mechanic has pulled off the Hydrovac and bypassed it for now. I brought it home yesterday. The only number I can find on it is on a brass tag attached to one of the bolts. That number is 378802.

On the end cover there is one of the tabs broken off where the long J-bolts go through that hold the end cover on. So I doubt this particular unit can be rebuilt, unless the rebuilder is able to repair that. So would probably need a source for a new one.

Also, I have not yet driven the truck since the Hydrovac has been removed, since it's still in the shop. So the jury is still out on whether to replace it at all. But my gut is telling me that I probably should.

White Post Restorations can rebuild your unit, they have the parts to replace anything that is bad.

That's the Bendix part number. You can search it on-line...

You really want and need the Hydrovac working. Modern cars stop way to fast and you need all the help you can get to stop your heavy truck.

Last time I called Precision they were one of the major Hydrovac rebuilders for companies like NAPA...you might reach out to them and see if they can help.

http://precisionrebuilders.com/

Mike B

EDIT, here's White Post's info https://whitepost.com/brake-sleeving-rebuilding-services/

Thanks, Guys! You've given me some good options to check out. I will be looking into them after the Holidays get over with.

I bought a totally new hydrovac for my 1948 2 ton from Vehicles for Victory. The one in my truck was not repairable, and it was plug and play, perfect fit. Not sure if it's different for you truck.

https://vehiclesofvictory.com/store/vov-reproduction-parts/

I sent mine to this guy, he did a rebuild and works great. They had to sleeve mine, but all turned out well and truck will stop great.

https://www.brakematerialsandparts.com

I had a snapped tab just like yours and cardone was able to fix it along with replace a j-bolt. Did it look factory? No, but it got the job done and doesnt look horrible.

How do you bypass the Hydrovac? Do you just connect the brake lines that go into the unit together?

Hi DelawareTruckGuy. I bypassed my Hydro-vac by doing that, one brake line is an input, the other is output, disconnect both from the Hydro-vac and couple them together. Bleed the system like you would a system without the Hydro.

I am assuming the Jack oil goes into the port plug on top of the hydrovac. How much Jack oil do you put in? Is it fill till it overflows, then put plug back in after it stops draining? I have never driven mine or started the engine yet. My master cyclinder was froze, I removed it today. I don't know if the hydrovac works or not. Willing to try it before I invest in having it rebuilt. I may just bypass it for the time being or hopefully it will bypass it self internally as it is designed to do. I just bought my 1953 6400 the first of June. Haven't had much time to even look at it let alone work on it. This truck needs a lot of restoration time before it goes on the road. I really need to able to move it in & out of my shop & would like to have brakes when doing so. I am getting close to being able to try to start the engine. Thanks for any help. The above links for rebuilders & parts has been a great help.

dsbike, depending on the style of your Hydro-Vac, mine is a Bendix and the plug for the leather oil reservoir is low on the front, it will only allow a small amount of oil, just enough to wick into the leather and keep it supple. Don't fill anything from the top unless there is a sight plug in a lower location to check the level. The Bendix has only one plug for fill and check.

There is a small 1/8" pipe plug on the back of the sheet metal can, it gets 1 oz. every 10,000 miles or once every 6 month per the shop manual.

Mike B

Reman, Inc. Reasonable prices, people who know their subject, and they ship!

I ended up sending mine to this place. Just got it back a couple weeks ago. Now just have to line up an appointment with my mechanic to get it put back on the truck.

Got it installed a few days ago. So far I've only driven it from my mechanic's shop back to my place (just a couple miles) but it seems to work great. Looking forward to driving it a little more.

I drive mine as much as I can legitimize, it is not an economical machine, but I really enjoy using it if it fulfills a purpose. I recently added the two speed rear pumpkin, that has made a huge improvement in drivability as it allows me to keep up with traffic on the two lane roads. The brakes are great, no worries with the complete system being rebuilt.