Tailwheel
Member
- 71
- 58
- 18
- Location
- Charlotte, NC
I am posting this as a cautionary tale. Might save someone some real headache and huge amount of money, or perhaps their life. I'll try to keep it short.
A few months back my P/S pump took a shit at 65 mph with 12-bolt HMMWV wheels and 37" MTR's. Wasn't fun, almost didn't get it stopped before going through a busy intersection. Add to that the fact that I could barely turn with the stock Chevy steering arrangement.
I replaced the P/S pump with a PSC high-output unit with -AN fittings. I made custom steel -AN lines to replace my aged and cracked lines and I also purchased a Cordone rebuilt hydroboost which I shipped to Busted Knuckle Offroad (awesome folks) for a porting mod to fit the -AN lines. Fast forward to a couple months later and the system was running okay but would occasionally act a little funny when braking and the accumulator gave me fits and sometimes just didn't work. It then started to develop a leak where the hydroboost unit splits (not the brake master, the unit half) so I decided to replace the figure-8 seal. I ordered a seal kit from Pirate Jack (great quality).
Upon disassembly I placed the hydroboost in a large, deep plastic bin to catch oil/parts and carefully disassembled. I immediately noticed that the accumulator check valve assembly was very different from the diagrams I had available, so I carefully disassembled my original, untouched, GM hydroboost and it also had a completely different accumulator check valve assembly from both the diagrams and the Cordone unit (it was also severely damaged internally from P/S pump debris). I was stumped. I decided to carefully re-assemble the Cordone unit exactly as it came apart since it had sort of been working before it started leaking. I installed it, bled it, and everything seemed to be great, until I turned the steering wheel and pressed the brake at the same time while backing out of my driveway.
The unit exploded. I don't mean it broke or popped, or quit, I mean it exploded. There is a swaged fitting on the power piston that came apart internally, forcing the pedal rod to shoot out of the unit and into the cab. It bent my brake pedal up over 1" and damaged the bracket that holds the brake light switch. The drivers side cab (and me) was COVERED in power steering fluid. I have no idea what the pressure spiked to but it was well north of 3,000 psi I would assume.
I got lucky in the fact that I wasn't driving down the road, the pedal rod didn't go through my shin or foot, and the swaged fitting somehow didn't break so I was able to re-assemble and swage it.
I have since purchased a new rebuild kit, replaced all the seals, re-installed the power piston using a custom made spring compressor and a swaging tool, and installed a new accumulator check valve assembly WITH a BALL BEARING in the appropriate location, something the rebuilt Cordone unit did not have installed. I was able to pry the ball bearing out of one of the old check valve assemblies and re-use it. I'm not sure what size it should be, it looked kinda small to me but I went with it.
So, if you open up a hydroboost and things don't look standard, exercise extreme caution, and don't forget the BALL BEARING that actuates a plunger in the check valve assembly. Hydraulic pressure is no joke.
/rant
A few months back my P/S pump took a shit at 65 mph with 12-bolt HMMWV wheels and 37" MTR's. Wasn't fun, almost didn't get it stopped before going through a busy intersection. Add to that the fact that I could barely turn with the stock Chevy steering arrangement.
I replaced the P/S pump with a PSC high-output unit with -AN fittings. I made custom steel -AN lines to replace my aged and cracked lines and I also purchased a Cordone rebuilt hydroboost which I shipped to Busted Knuckle Offroad (awesome folks) for a porting mod to fit the -AN lines. Fast forward to a couple months later and the system was running okay but would occasionally act a little funny when braking and the accumulator gave me fits and sometimes just didn't work. It then started to develop a leak where the hydroboost unit splits (not the brake master, the unit half) so I decided to replace the figure-8 seal. I ordered a seal kit from Pirate Jack (great quality).
Upon disassembly I placed the hydroboost in a large, deep plastic bin to catch oil/parts and carefully disassembled. I immediately noticed that the accumulator check valve assembly was very different from the diagrams I had available, so I carefully disassembled my original, untouched, GM hydroboost and it also had a completely different accumulator check valve assembly from both the diagrams and the Cordone unit (it was also severely damaged internally from P/S pump debris). I was stumped. I decided to carefully re-assemble the Cordone unit exactly as it came apart since it had sort of been working before it started leaking. I installed it, bled it, and everything seemed to be great, until I turned the steering wheel and pressed the brake at the same time while backing out of my driveway.
The unit exploded. I don't mean it broke or popped, or quit, I mean it exploded. There is a swaged fitting on the power piston that came apart internally, forcing the pedal rod to shoot out of the unit and into the cab. It bent my brake pedal up over 1" and damaged the bracket that holds the brake light switch. The drivers side cab (and me) was COVERED in power steering fluid. I have no idea what the pressure spiked to but it was well north of 3,000 psi I would assume.
I got lucky in the fact that I wasn't driving down the road, the pedal rod didn't go through my shin or foot, and the swaged fitting somehow didn't break so I was able to re-assemble and swage it.
I have since purchased a new rebuild kit, replaced all the seals, re-installed the power piston using a custom made spring compressor and a swaging tool, and installed a new accumulator check valve assembly WITH a BALL BEARING in the appropriate location, something the rebuilt Cordone unit did not have installed. I was able to pry the ball bearing out of one of the old check valve assemblies and re-use it. I'm not sure what size it should be, it looked kinda small to me but I went with it.
So, if you open up a hydroboost and things don't look standard, exercise extreme caution, and don't forget the BALL BEARING that actuates a plunger in the check valve assembly. Hydraulic pressure is no joke.
/rant