I installed a hydra-boost brake booster in my car a while back and have had issues with it since the install. I get a good bit of groaning form the pump and the booster gets hot, I’ve tried a few things to resolve it.
I’ve done a good bit of research on the internet and actually stumbled across a tech write up by who I believe is someone from Hydra-tech brake systems. He described a couple issues in detail that I’m experiencing, groaning and push back on the brake peddle when depressed and heat buildup in the booster.
He explains that to much pressure on the return hose will cause the booster to build a lot of heat and will cause a slow peddle return once depressed.
He recommended staying with the 2.0 to 2.4 gpm from the pump as GM did.
He recommends -6 AN (3/8”) lines for the supply and return lines and ½” (minimum) for the line from the remote reservoir to the pump and that if anything smaller was used for the line between the pump and reservoir the pump will cavitate and always run noisy.
I decided since I had my system apart due to line rupture I would try and address as many of his recommendations as I could.
I took my remote reservoir apart and took a close look at all the fittings and lines. The outlet of the reservoir is a 3/8 NPT to -10 AN fitting, first issue. The 3/8 NPT fitting is too small for the supply to the pump per his recommendations of no smaller than ½”. I’ve checked and have room to drill and tap to ½” pipe to gain the recommended size and will install a -10 AN to ½” NPT adapter.
Reservoir Return line fitting size (drill bit inserted into fitting) and the reservoir to pump fitting (-10 AN to 3/8" NPT);
The pump discharge is -6 AN PTFE SS lines with an internal diameter of .293” (a little below the recommended 3/8”). The returns form the R&P unit and the Hydra-Boost unit is also -6 AN line and is tied together with a Tee at the reservoir, not exactly what he recommends but close.
Distribution fitting in reservoir;
On the internal of the reservoir is a distribution fitting with an internal diameter of .247” well below the recommended 3/8”. I believe this fitting is one of the main causes of the pump groaning, the reason for the heat build up in the booster and the slow return of the brake peddle which is caused by to much pressure in the return line to the reservoir from the booster. To resolve the issues with the return line I plan to remove the OEM distribution fitting and fab my own distribution nozzle for the reservoir. If the restriction was closer to the steering gear and away from the reservoir (Tee) it would not effect the booster operation.
Reservoir Return line fitting size (drill bit inserted into fitting);
He also recommends using a remote reservoir with a separate return for the Hydra-boost to eliminate the issue of to much pressure in the return line along with a reservoir with an internal filter for correct de-gassing of the steering fluid.
I’m going to weld a bung on the side of the reservoir or drill and tap a 3/8" NPT hole for a separate fitting in case the new distribution header don’t resolve my issues I can move the return from the booster to its own rout.
He explains that the booster is an open center hydraulic device meaning the fluid flows freely to the booster and own to the steering gear until the brakes are applied.
From what I can find on the net the steering gear is also an open center device meaning the fluid form the pump flows through the gear and back to the reservoir without obstruction until the steering wheel is turned and force is applied to the torsion lever in the gear. This being the case than the return line will need to be sized to flow the pump output flow without restriction. So if the fittings at the reservoir cause restriction than there will be pressure on the return line causing issues with the booster. This would support having a dedicated return fitting at the reservoir for the booster.
One other issue he explains is that the reservoir has to be vented at the cap. If the reservoir is allowed to build pressure from thermal expansion enough pressure can build in the return line and cause the brakes to self apply.
I may have to replace the reservoir if I can't work these issues out. The reservoir I have came with the Zoops serpentine drive unit I have on my engine.
Anyone else have this type of issues with their Hydra-boost install?