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HB problem found. Not HB problem rear drum problem.

sandawgk5

sandawgk5

3/4 ton status
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I just got the Hydro-boost installed I also did some mods to the pump as in I stretched the spring to 2 1/4" removed 1 shim of the 2 in my valve as well as shaved some off the piston. I also drilled the orifice out slightly larger and notched the end for flow. I am starting with a completely dry system as in I installed a cooler, box is empty due to sector shaft changout, pump was dry due to the mods, hydro-boost is dry and came from an 86. I filled the pump and started the truck, worked the wheel back and forth for about 3 hours total. I have put about 3/4 of a gallon of fluid in the system. I have no leaks. The pump is still sounding like it has tons of air in it especially when the brakes are pressed. That is problem #1. How long does it take to get the air out of the system? Now to the major problem. We went to take it for a spin and make sure the detroit was working and everything was in order. Put it in reverse and truck barely moves backwards RPM is about 1200. I give it gas and it moves but acts like the brakes are on. We take it down the block and back and all works fine other than the grinding sound of the pump and the rapid stop due to dragging brakes. We park it get out and the rotors are HOT. I start the truck again and notice that the pedal moves down as if someone is pressing it and the brakes come on. Is this a problem with the pushrod between the booster and the MC? There is no spacer between the two the are bolted directly together. Can I grind the pushrod down? The pushrod for the booster is identical to the vacuum booster I removed and it bolted up fine and attached to the pedal fine. Any help is greatly appreciated I gotta get it fixed to go wheelin Saturday.

Thanks

Ira
 
Last edited:
The spring pulls the pedal up to the drivers seat. The booster coming on line when I start the engine overcomes the spring and pulls the pedal down.

Ira
 
Also, if you live somewhere where it gets hot, or you're gonna drive it hard, I'd recommend adding a cooler for the fluid. Since it has to go on the low pressure return line, you don't want any significant back pressure due to the cooler (back pressure on a H-B can cause the brakes to remain applied), so use a cooler that is fairly large. Or buy the one Chevy puts on their extra heavy duty trucks with H-B.
Click to expand...

Could this be my problem? I have the Hydroboos and Steering box teed and both run through the cooler. The cooler I used is the old tube type that used to be my tranny cooler. I have a Hydroboost pump available with the extra return nipple maybe I should just put that on and try it. Still looking for ideas and if anyone else has had this problem.


Ira
 
I remember that "T" and how much fluid can come out of it in short order....but that is a whole other conversation:haha::haha::haha:

I would doublecheck the way the lines are run and perhaps bypass the cooler for a while to see if it helps.
 
MC sticking?
Did you adjust the rod between the pedal and the HB unit. If it is too long it could always apply the brakes. I would lean towards that.
 
I'm having the same problem, but since I'm using this in a non GM application, I figured it was my home made bracket. It dragged so bad it wouldn't roll. But if I pulled up on the brake pedal, I felt a little click and the brakes would release.
Now I teed the return line from the hydroboost and P/S together. So that back pressure issue could be part of my problem. I had been think of putting a remote reservoir to insure a sufficient fluid supply, [someone posted that the hydroboost pumps hold more fluid] with the cooler between the pump & reservoir. This would alleviate the back pressure if that is the problem. I'm just not sure how those remote systems keep from overflowing at the pump?
I'll be watching this thread to see your cure.
Good luck
 
is the rod from the brake pedal to the cylinder straight?when I added hydr to mine the rod was on an slight angle and caused the piston to not come all the way out..........
 
I am thinking since I did the pump mods there is abnormally high pressure on the return side of the steering box causing increased backpressure on the HB unit which intern is applying the brakes slightly. I have a HB pump and rez in the garage that I am going to change out today and see if that helps. Do I have to remove the pulley to change the rez?

Ira
 
Yes, but wouldn't it be easier to just change out the valve from one pump to the other. You might even be able to do that without even removing the pump....just depends on how much room you have back there.
 
I want to use the rez with the two return lines. That way the steering will provide no backpressure on the HB unit. It will have its own return to the pump rez which in theory is vented to atm. Only the steering will run through the cooler.

Ira
 
Well the brakes do not drag anymore:D . I put a HB pump on and increased the flow by boring the orifice and notching the end. I drove the truck around for a while and I have a problem with the brakes vibrating hard when I step on the brakes. It is not felt through the pedal it almost feels like a warped rotor. The brakes I was told only have about 1000 miles on them. Is it possible for a rotor to warp by having the weight of a 60 sitting on them on the floor? Could the increased flow from the orifice be causing this. I would think if it was the HB unit it would be felt in the pedal. Brakes work REALLY good other than the vibration. Pedal is a little low and spongy, prolly need to power bleed like the tech article says, but it stops pretty good and had no lock up. Any help with the new problem would be great.

Ira
 
Bend from just the weight of the 60.....doubt it.

Use your dial indicator and mag base to check the run-out. Should be less that .005 after a fresh turn. Any more that .020 is bad
 
Oh Ya when I seperated the return lines rather than running a Tee the system was bled out in like 5 min. Talk about a kick in the balls:o .

Ira
 
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