hydroboost bleeding process

[K5dreamer]

so ive got a reallllly spongy brake pedal, the light turns on every time i stop the truck, so i crawled under and checked things out. sure enough despite dry sunny weather, my driver side drum is soaking wet. looks like a blown brake cylinder. so, ive got all the parts, drums, shoes, brake cylinders for both sides, new brake fluid, and the tools, but i just stopped and realized ive never bled a hydroboost brake system, and from what i understand they have much higher pressures than regular systems.

is there anything special i need to know about bleeding these brakes? or is it the same as regular brakes where you have someone stand on the brake pedal, and you loosen the bleed screw enough to let out some fluid, and tighten it back down?

thanks all. imma get to replacing parts, ill wait to bleed till i here from yall.

 

[dremu]

Uhh, the brake side of a hydroboost system is just like a vacuum boost one, so go bleed it like you usually would. I prefer the garden spray pressure bleeder 'cuz I don't have a helper, but you have a wide variety of options.

Whoever told you that the pressure is higher was smoking something ... maybe they were thinking of the boost side, i.e. the power steering side

(Now, IIRC brake lines can get to something nuts like 1200psi or somesuch, but that's true of all hydraulic brakes and has nothing to do with the booster type.)

-- A

 

[K5dreamer]

*smacks forhead*

wow...... less beer, more wrenching, thanks man, dunno why i didnt realize the brake side was no diff. good lord..... ok, im out. thanks again.

 

[ryoken]

vacuum boost brakes run max pressures of 1000 to 1500 lbs.. hydroboost run 2500 to 3000 lbs...

as for bleeding, i'm guessing the procedures and or tools are the same...

 

[dremu]

vacuum boost brakes run max pressures of 1000 to 1500 lbs.. hydroboost run 2500 to 3000 lbs...

as for bleeding, i'm guessing the procedures and or tools are the same...

Eh? The calipers on the front of, say, a C20 sixpack are the same as an SRW C30, and one would have a vacuum booster and the other hydro ... so the hydro provides more pressure? Seems like it'd blow something.

-- A

 

[ryoken]

http://www.vancopbs.com/category_s/66.htm

"
[FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]These are hydraulic units that work off your power steering pump. It's like using a hydraulic ram to operate your master cylinder. The idea is very simple. They put out enough pressure and volume to make any current brake system stop the vehicle you're driving. [/FONT][/FONT]

[FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]Vacuum boosters put out between 1,000-1,600 lbs of pressure to your brake system. The hydroboost puts out between 2,400-3000 lbs of pressure to your brake system. This is basically giving you the power to stop the vehicle. It's the actual clamping pressure your calipers or wheel cylinders have to clinch onto the rotor/drum. [/FONT][/FONT]

[FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]Hydroboost have a shaft in them that directly operates the master cylinder. So when you are applying the hydroboost you only move the brake pedal 1/16 of an inch before you're applying the master cylinder. We also incorporate a much bigger master cylinder then a stock master on most vehicles. The combination of these two things severely shortens the stroke it takes to make the vehicle stop. The entire full stroke of a hydroboost is only 2.5 inches. You actually come to a full stop in your vehicle within 1 inch of brake stroke. If the booster should fail you get one power brake application. After that it reverts to true manual brakes. Since the shaft directly operates the master cylinder a failed hydroboost is twice as easy to stop then a failed vacuum booster. It will be a hard pedal, but foot pressure will work. [/FONT][/FONT]

[FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]Even though they put out all this pressure they are not sensitive. The pedal feel will be firm, with the more pressure you apply the greater braking force you get. It is something you want to get used too. If you've never driven a vehicle with a Hydroboost, it gives you braking pressure you've never had before. ."[/FONT][/FONT]

 

[dremu]

Dayum. That's the place that ports and polishes and whatever the hydro units, right?

I learn something new every day ... glad I changed my title over there <---- to "Mister Electric" from "Mister Brake"

Well, 'splains why you get better braking and holding with the hydro then. And to the OP, I stand corrected, though the bleeding process is the same as for vacuum.

-- A

 

[ryoken]

just crash coursing myself recently...

picked up a complete unit from an 85 in here, pedals and all.. gonna send the booster out to Vanco for the flow mods.. Then I'm going psycho on the pump, ressy and cooler for the rest of the system... PSC stuff...

I figure steering, hydro-assist AND brakes is alot of responsibility, and deserves the coin and attention..

 

[K5dreamer]

well, both master cylinders are replaced without incident. but.... both adjusters are seized solid, i couldnt break them loose with a long screwdriver and channel lock pliers. so i need to get new ones tomorrow. and, it turns out the wet drum was actually due to a blown axle seal. i thought i had those, but i cant find em, so i guess ill buy new ones with the adjusters. fun fun. ive got all the axle lube and g80 additive, and the diff cover gasket, just gotta do it. just figures ya know? and im tryin to meet up with a friend while she's in town tomorrow, and the truck is on jackstands