Hydroboost help for the love of god!!!

B

BIG HEAD CHRIS

New Member
Joined
Oct 22, 2004
I am contemplating hanging my self with the braided lines I built for my HB conversion. I've blead the brakes eleven thousand times, and are fairly confident there is no air in the lines, but i still cant get a pedal when the car is running. I used the H/B and master cyl for a 85' gn. Am I missing somthing on the pedal/ rod legnth or somthing? I hate to sound like such a dork, but I have been f^$&ing with this thing for over a month, and it's getting very,very old. Thanks in advance for any suggestions ,Chris
 
When you bled the brakes, did you get a strong squirt out of the calipers and cylinders? Also, are you sure your lines are routed properly? May be a bad hydroboost unit.
 
Have you driven the car???? Maybe your just not used to the feel of hydroboost. Sometimes you need to drive it to really get a feel for whether the air is out or not.
 
Did you attempt to bench bleed the master cylinder prior to putting the master cylinder on the car? Bleeding brakes can be a severe PITA......keep us posted.
 
The ps lines need to be connected to specific ports and if you reverse them, you will get a low pedal and / or no power assist. Additionally, did you back the parking brake adjuster out, then readjust the rear brakes, followed by the parking brake adjustment?
 
When I did my AstroVan HB conversion on my '87 GN.... I bench bled the m/c on my work bench... in a vise..... and installed it on the HB unit...... used a stock hose for the GB to HB from an '85 GN and a modified stock HB to PS pump hose from an '85 GN..... Once everything was installed and hooked up on the HB.... I installed the freshly bled M/C and topped it off with fluid.... and actually drove the car w/o bleeding the brakes at all..... worked great. I might have a slight amount of air in the system... but the pedal feels great.... and the car stopped great. Once I finally get the engine back in it... I'll probably bleed the system real good to get the old fluid out of the calipers and brake lines.

Sorry to hear you are having trouble.
 
I bench bled the M/C. The car is on stands w/o wheels. The pedal is extra firm when the motor is off. Crank it up and the pedal goes spongy, and I can push it all the way to the floor. Car running, I get on the brakes, bring the car up on the converter, and the brakes won't hold anything. I'm confident the lines are routed properly. With a friend working the pedal,motor off, the fliud did come out with some pressure behind it, out of the rears. I rigged up a power bleeder of sorts with an aluminium plate,a metal valve stem,and a bicycle pump. That ,I think got all the air out of the rear circut that I was chasing. The results were the same,sh!^^y pedal,and no holding power. I know the pedal will feel different,but it shoud'nt go to the floor,right? Thanks for the ideas keep em' comming please! Thanks, Chris
 
All components,H/B, M/C are 85' GN parts. The lines are routed like this(as mounted on the car) :port on the PS pump to the port on the PASSENGER side of the HB. DRIVER side HB port to the STEERING BOX's forward most port. The return line from the steering box to the resivour. The other return line in the top of the HB unit is routed to the top of the Resivour via a bulkhead fitting. Thanks,Chris
 
Chris,
It still sounds to me you have air in the system. I have had good luck using a vacuum pump to bleed the brake system on my car.
 
It sounds like air in the system to me too. If your confident you have all the air bled out then maybe its time to try a new hydroboost unit.
 
Drive it!

Every Hydroboost system I've ever worked on has a crappy pedal feel with the car stationary. If the pedal feels good with the engine off, and feels almost "springy" with it running, I'd say put the wheels on it and drive it, you'll probably only use a fraction of the pedal travel to get the thing to stop. Make sure that your rear brakes are properly adjusted, and keep in mind, a drum brake system isn't going to be able to hold all of the torque these cars put out without the help of tires on the pavement.
 
The pedal should not go to the floor even with the car sitting still. I would not take the car out on the road. Is this system directly from an 85 GN or is it from the parts store? If it was from an 85 GN, did it work on that car? The hydroboost sytem should give a firm pedal after only 3/8" of travel. Not spongy and going to the floor. Does it feel as if it wants to grab at certain positiions of the pedal? The reason I asked is if it is a rebuilt unit, sometimes their valving is off enough that the piston in the booster is pushing the valve in the master past the point of applying pressure to the brakes. You may need to use a spacer between the master and the booster.
 
Thanks Robert,and everyone else for the good info.I am going to try bleeding the system again. Is there any difference in the pin placement on the pedal from 85' to 86/87's ? Thanks,again, Chris
 
I am not sure about the pin placement on the '85 but I can tell you my stock '87 pedal sets out further (toward driver) with the hydroboost compared to the powermaster. I had to adjust my brake switch quite a bit to get it back in the right location.
 
Thanks everyone for their insight to this gnarly problem. I got brakes!!!! Their was still air in the brake system ,like you all said. After re bleeding them for the nineteenthousand and first time I've got pedal for days,and a car thats mobile again!!! Thanks again to everyone, Chris
 
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