GoldHawg
01-10-2010, 04:45 PM
I have the complete hydratech hydraboost conversion for my 71 GM A-body. Bought it from SC&C, and after the install the brakes bite like nobodies business, but the pedal doesn't seem to come all the way out. I understand that there may be air in the fluid, and you have to drive 500 miles. I've done that now and and yet it still doesn't seem to come out as far as it should. I have to take my foot and pull the pedal out to get it to come the rest of the way. And the wheels also don't spin freely with the pedal released, they'll spin but there is definite drag.
Today I tried adjusting the rod going from the pedal into the booster. Getting better (tried both directions, couldn't mentally be sure which way was best) but it still seems like the problem is the hydraboost does not push the rod back far enough.
thoughts/
GoldHawg
01-10-2010, 08:59 PM
I'll call Marcus tomorrow and see what he says.
Marcus SC&C
01-11-2010, 09:41 AM
It`s probably just a minor tuning issue. Check this link out and see if anything stands out as different. http://www.angryamerica.com/chevelles/hydroboost.html (http://www.angryamerica.com/chevelles/hydroboost.html)
Particularly make sure you`re using the proper brake pushrod hole in the pedal.
If that doesn`t take care of it then run a return circuit back pressure test.
A quick test you can run to rule out restrictions or problems in the low pressure return line plumbing if you are running a T fitting arrangement: Place a towel under the brake assist unit to catch any PS fluid, then disconnect the low pressure return hose from the brake assist unit's low pressure return nipple and temporarily plug this hose. Then perform a complete bypass of the low pressure return line circuit by connecting up a suitable temporary hose to the brake assist unit low pressure return line nipple, and then running the other end of this hose either into the "mouth" of the PS reservoir or into a windshield washer jug. The only time you will see any real flow from the low pressure return nipple on the brake unit is when you are releasing the brakes, at which time the brake unit will exhaust roughly a couple tablespoons of PS fluid. When your foot is not on the brake, there should only be a drip, drip, drip (if anything at all) coming out of the brake unit's low pressure return. If you find the PS system does not heat up anymore and basically acts in an improved fashion, then this indicates that there must be a bottleneck or restriction of some sort in the low pressure return line plumbing that must be reworked to remove restriction as needed.
Additional FYI - When your foot is not on the brakes / brake unit not applied, it is literally a port to port interconnect on the brake unit. Spoken a different way, the hydroboost unit is an open center hydraulic device, which means that it is invisible to the PS system when the brake is not being applied = it may as well just be part of the high pressure hose between the PS pump and the steering gear. That being stated, make 100% sure that the brake pedal rod adjustment under the dash isn’t set too aggressively, as we have seen brake light switch and rubber pedal stop bumper adjustments at fault for not allowing the brake unit to go into a full state of release = back off the pedal rod adjustment if needed to make sure that there is zero preload on the brake unit input piston when the brakes are not in use or temporarily disconnect the brake pedal rod linkage entirely. You can also take a rubber tipped blow gun and blow back and forth through the high pressure ports on the brake unit – make sure to have a towel handy as some fluid will blow out. If you cannot blow through the high pressure ports on the brake unit, remove the master cylinder and then tap the master cylinder pushrod inward firmly using an average hammer, as this will force a sticking pressure control valve inside of the brake unit to free up (if some fleck of debris has possibly gotten into it and hung it up).
Also pop the power steering cap loose when hot to see if a bunch of pressure has built up from thermal expansion. If so, this pressure will cause the brakes to not release, and you should install a vented PS cap or a different reservoir.
Give that stuff and try and you should be able to get it sorted out. Mark SC&C