View Full Version : Hydrovac Brake System

11-07-2006, 05:25 PM
First time N8 drove my Hawk with hydrovac he put me into the windsheild. There was a kit to reduce pedal pressuse, but they were always a little "grabby"

Arnold Md.
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11-07-2006, 05:54 PM
The 55 Speedster has a hydrovac brake system. I had the master cylinder, front wheel cylinders and front brake shoes replaced as all these cylinders leaked. The brake shoes were replaced because the right front shoes were completely soaked with brake fluid.

When I drove it back home, I was surprised by the "feel" of the braking as compared to brakes without the hydrovac. I expected it to act or feel like a modern car with power brakes in that braking should be firm and immediate. When I brake normally, the brakes do not respond very firmly but I noticed if I really stepped on the brakes hard, the braking is immediate.

Hoping that my description makes sense, I would appreciate any comments how this system should respond or "feel" when brakes are applied in a normal stop.

Thank you in advance.

11-08-2006, 01:06 PM
I don't seem to get much boost with the Hydrovac on my Speedster. They are more like unassisted brakes, which grab progressively better with increasing pressure. They are certainly not like modern assisted brakes that have a much lighter pedal feel. I'm still wondering if my Speedster's are working properly. The Hydrovac was rebuilt a while back and there are no fluid or vacuum leaks that I can detect.

Mike with Speedster

Dan White
11-08-2006, 03:13 PM
My R1 Hawk's hydrovac works much like a modern system, probably more sensitive than most new systems. If you step on it you will be through the windshield and will lock up all 4 brakes. Of course I had the unit rebuilt about 8 years ago and have gone through the entire system to make sure everything is up to snuff. I noted before that you are supposed to add 1oz of neets foot oil per year in the little hole (plugged with rubber stopper) in the back of the hydrovac vac cylinder. If that has not been done for a long time the system will most likely not work. My R2's Hawk's system does not work properly and is much like you have described. It does not look like the unit has been serviced in many years. I plan to get it rebuilt this winter and have it running by next summer for the 2007 Nationals. I believe JP can get your unit rebuilt, and if you do you will need to add the neet's foot oil before you hook the unit up, they usually come dry. Also make sure the check valve in the main vacuum line is working properly.

Dan White
64 R1 GT
64 R2 GT

11-08-2006, 06:27 PM
Thank you for your replies indicating that two cases are as I described and two cases of how I thought the hydrovac should function.

When I bought this car, I also received all receipts of extensive work done in 1995 including a rebuild of the hydrovac by Studebaker Parts & Service in Maynard, MA. For some reason, only 2000 miles were put on the car since that time.

Since it seems that another rebuild should not be needed, I concur with the comments that these units need service and upkeep. The shop manual states that causes for non-operation are: low or no vacuum, clogged or restricted lines, defective check valve and clogged air filter.

I have removed the air filter and found it clogged. The shop that did my brakes will re-bleed all areas including the two bleeder valves on the hydrovac and I will have them check the vacuum and vacuum check valve. I will install a new air filter. I am not familiar with the oil recommended to be put in the rear of the hydrovac. Please advise. My unit has a metal plug.

I will let you know if the operation of the hydrovac changed after all actions are completed.

11-08-2006, 08:33 PM
Use neatsfoot oil for lubing the leather seals in the booster unit. You should be able to find it at a shoe repair place. (hopefully you still have one around.)


55 Commander Starlight

11-09-2006, 09:06 AM
It is my understanding that most Hydrovac rebuilds involved changing away from using the leather seals and using some form of rubber. How does that affect the use of Neetsfoot Oil? It might be good for leather, but not so good for some types of rubber. Is something else recommended for the newer rebuilds?

Mike with Speedster

John Kirchhoff
11-09-2006, 12:05 PM
If you need neatsfoot oil, I found some at Ace hardware.

Dan White
11-09-2006, 02:58 PM
That is a good question about the seals maybe being updated. I had assumed that you still needed to add the neetsfoot oil, but I do not now. Maybe JP knows since he has had several rebuilt?

Dan White
64 R1 GT
64 R2 GT

05-23-2009, 09:00 PM
How much neetsfoot oil goes in the hydrovac??
Brian C

Dan White
05-23-2009, 10:13 PM
1 oz.

Dan White
64 R1 GT
64 R2 GT

05-26-2009, 03:07 AM
I have been wondering about The "Power brake system" on my hawk(61) a while now, I hav other cars with power brakes from the 60's however the Studebaker system is very antiquated. It requires alot of pressure to stop the car. My pre war Studebakes brakes are better. I have a rebuilt Hydrovac system and found the leeds foot oil. All new brake componets. I have reajusted the brake shoes, put new spring on the pedal. The car stops however with alot of nervous antisipation.Who knows maybe I need a Studebaker tech to adjust them.

Studebakers forever!

Dan White
05-26-2009, 06:34 AM
Believe it or not the Hydrovac system was used on a lot of vehicles besides Studebaker. GM used in on some 1950s cars (including Cadillac), Mercedes Benz used it on cars in the 50s and 60s, Ford, GM, and International used it on some of their their trucks into the late 80s, Ford used it on some cars including Lincoln into the early 80s. So it is not as antiquated as you might think!

Dan White
64 R1 GT
64 R2 GT

05-26-2009, 08:21 AM
The hydro-vac when working properly will offer a noticeable improvement in braking allowing less pedal pressure to attain braking. They are nice when up to snuff. jimmijim

05-26-2009, 08:36 AM
If, with your hydro, you really have to exert a lot of force to stop, you may have two problems.

One) (not so easy to fix) ) the Hydro may NOT be operating properly.

two) (moderately easy to fix) look at the frame, in front of your master cylinder and check if the car has the factory power brake pedal installed. This is a short pedal (8") which pivots on a peg, bolted to the frame, about 5" in front of the standard brake pedal peg, which is welded to the frame. Changing to a standard brake pedal (11.5") and a short actuator rod, will give you enough mechanical advantage to STOP if your Hydro fails.

I'm not certain which models other than sedans used this short pedal, but you never know what kind of "sausage" was made with a car 40 years old.

Bob Johnstone

64 GT Hawk
55 President State Sedan
70 Avanti (R3)