Hydraboost - ? about getting it going...

[69MyWay]

Anybody here put a hydraboost off a heavy duty truck on their hot rod?

(Not a hydratech unit, just a unit off a 83 Chevy truck)

I installed one on my 69 Vette. I made sure it mated up to the correct depth piston master cylinder.

So far the brakes don't seem to work. The pedal goes to the floor then kind of kicks back while it is running.

Any special air/bleeding issues with one of these units?

I have had them on 1 ton trucks, motor homes, etc, but never had one off and on before.

[Twin_Turbo]

run the engine for some time and keep adding fluid to the reservoir/checking the fluid level. There's air in the syhstem and it'll take a short while for it all to get pumped out. You have a power rack installed right?? Is it giving assist or not (probably not)???

[69MyWay]

The rack appears to be working fine at this point. The air purged out of it pretty fast. However, I manuall ran the rack left and right many times while adding fluid before lowering the car to the ground.

When I apply the brake I can see the pressure lines on the booster jerk as if they are getting a surge of pressure through them, just no assist taking place.

I have only run the whole set up for a few minutes at this time, but have spent 1/2 hour or so bleeding the brakes as I had them open for a bit. I bench bled the m/c and even ran a bench bleed line on it after it was in the car to make sure there was no air in that part of the system.

[sinned]

They bleed very quickly and easily. I suspesct you have a base brake issue rather than a hydroboost issue. Bleed, bleed, then bleed some more.

[69MyWay]

I can't rule out a regular brake issue, so will continue to bleed.

Here is what I found doing some research. I found a bronco group doing this swap and they ran into problems with the return line being "T'ed" into the power steering return line. It can create a restriction sensation to the unit.

The solution is to plug a second line into the resevior (like the actual Chevy trucks do).

The test is to run the return line into a catch can. Start the car up and test the brake. If the pedal comes right up and it works, then I have to re-route the return. If no change...then I am going to consider again issues with the brake fluid/air and or a bad hydroboost unit (bought it used from the j/y).

[Hydratech®]

It sounds like you may have the high pressure lines hooked up backwards. With the pressure lines reversed, you will have proper PS functions, though will have no brake assist until you crank the steering wheel up against a steering stop = try that real fast and see what happens. Also, note that these systems will provide a true manual brake interface with the engine off = if you can't get a good pedal with the engine off, you certainly will not have a good pedal with the engine running (assist unit powered up).

Here are the port ID's:





Also, the whole return line T fitting issue IS actually just fine, though most all plumb it in incorrectly - click here for the facts: http://www.hydratechbraking.com/foru...topic.php?t=38

Depending on various factors, you may also be misinterpreting what you are feeling in the brake pedal. The best answer here would be to securely raise the rear wheels off the ground, then see if you can stop the wheels from turning against engine power by applying the brakes.

Let us know what you find