Like Rich said, I just so happened to be surfing through, so let's hit the scenario with tech! The more you understand the system, the easier it will be for you to work with of course, so let me take you for a general tour of what makes these things tick.
First, we do insert a
separate T fitting service note sheet in the instruction envelope with every outbound system. Here is a link showing a copy of this page:
http://www.hydratechbraking.com/imag...ervicenote.jpg
Here is a low pressure return line test you can run:
Excessive back pressure in the brake assist unit’s low pressure return circuit can cause PS system overheating and brake self apply. 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.
Note that you must also verify that your PS fill cap is of a vented design. If the PS fill cap is not vented, pressure will build up inside of the power steering system due to thermal expansion. This pressure will exert pressure against the back side of the power output piston inside of the brake unit, and may cause the brakes to start self applying as a result when warmed up. If you should experience this, pop the PS cap loose – if you hear a release of pressure similar to opening a carbonated beverage and the brakes are no longer dragging / self applied, then this indicates that your PS fill cap is not venting to atmospheric pressure. The obvious fix here would be to replace the cap with a vented design, though some have also found their success in using a pin drill to carefully provide venting.
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).
As mentioned above, these types of brake assist units are an open center hydraulic device, meaning that the PS pump output simply flows through the valving of the brake unit on its way to the steering gear box. The hydraulic brake assist units also function like a steering gear box does, in that the harder you crank the steering wheel, the more it will load the PS pump - it is the same with the brake assist unit. You will find that if you where to crank your steering wheel full right / left against a steering stop, that this will also load the PS pump the same amount as applying heavy pedal pressure on the brakes. This also means that you can perform a complete bypass of the hydraulic brake assist unit by disconnecting the high pressure inlet line from the brake assist unit and instead connecting this PS pump high pressure pressure line straight to the high pressure inlet of the steering gear to diagnose potential PS pump / steering gear issues (meaning you can take the hydraulic brake assist unit out of the loop by rerouting the lines temporarily).
Before you consider reworking any aspect of your installation, I advise the vehicle be put up on a hoist securely, and then observe how much pedal pressure is required to overcome the wheels from spinning under engine power. What you will see is that you are not having to apply more than approximately 40-60 pounds of pedal effort, which won't load the PS system much. Applying moderate pedal pressure will usually only drop an idle speed about 50-60 RPM. Applying 100+ pounds of pedal effort will typically load the PS system enough to drop the idle speed about 100-125 RPM - same as cranking the steering wheel against a steering stop. If you have a radical cam in a naturally aspirated build, it is already struggling to idle, especially with an auto trans with a convertor that is on the tighter side. Applying the brakes heavily (meaning taxing the PS pump) on an engine that is already barely capable of idling can be enough to make it look like it's killing the engine, especially if you are running full time vac advance on the distributor (as the vacuum starts dying under load and then the timing goes lazier and then the engine stalls...). EFI installations are typically immune, as the idle air control compensation will counteract the loads.
Summary? You may not need to tear back into the system at all, only needing to go out and run the vehicle down the road for a few miles. We typically find that the installations will settle down nicely after about a 40 mile round trip, especially if you can keep the engine RPM's mellow (to help prevent aeration of the PS fluid from getting aggravated by high pump RPM).
Here are a couple of links that may also help:
https://lateral-g.net/forums/showthread.php4?t=15052
https://lateral-g.net/forums/showthread.php4?t=10930
Let us know what you find!
