• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

Hydroboost help needed

Joined
Apr 5, 2025
Messages
7
Just upgraded to hydroboost. Saginaw pump. The resovior is overflowing when i pump brakes with motor off. I’ve turned wheels lock to lock about 90 times. I pressed the brakes three times after. This makes the reservoir overflow. The level is staying at the cold mark. Not sure what to do next. I’m kinda on my own here with nobody to help. Thanks.
 

73azbronco

Contributor
Bronco Guru
Joined
Nov 11, 2007
Messages
8,223
Is there a squealing noise like it's not bled? Wheels lock to lock 90 plus time with wheels jacked up off the ground, a lot? PS filter? Cooler?
 

nvrstuk

Contributor
Just a Bronco driver for over 50 yrs!
Joined
Jul 31, 2001
Messages
9,417
Loc.
PNW
Yea jacked up. No filter or cooler. No squeal but could here pump groan when at full lock and when hit brakes.
Don't hold the wheels full lock when bleeding the system with engine running.

Fluids don't compress, but air does. How full is your reservoir? 1/2" from top? 1" from top?
Does the system only burp fluid when pumping the brakes and NOTHING else (engine not running)? Send a pic of the hose routing like mentioned before. Either this or air is still in the system.

I believe there is STILL a HB line routing schematic on this site that is incorrect. I know because I routed my lines as per the schematic and they were backwards. Found the "other" line schematic and it's worked great for a dozen plus yrs.

What happens inside the reservoir when you hit the brakes, engine running and NOT after turning the wheel lock to lock? Can you see the small amout of fluid returning to the reservoir from the HB unit?
 
Last edited:
OP
OP
S
Joined
Apr 5, 2025
Messages
7
Don't hold the wheels full lock when bleeding the system with engine running.

Fluids don't compress, but air does. How full is your reservoir? 1/2" from top? 1" from top?
Does the system only burp fluid when pumping the brakes and NOTHING else (engine not running)? Send a pic of the hose routing like mentioned before. Either this or air is still in the system.

I believe there is STILL a HB line routing schematic on this site that is incorrect. I know because I routed my lines as per the schematic and they were backwards. Found the "other" line schematic and it's worked great for a dozen plus yrs.

What happens inside the reservoir when you hit the brakes, engine running and NOT after turning the wheel lock to lock? Can you see the small amout of fluid returning to the reservoir from the HB unit?
Engine off, when slowly hit brakes the fluid slowly rises. When turning wheels back and fourth engine off, the fluid rises and lowers. Overflows if turning wheels too fast. Reservoir Is at cold mark. I’m getting no level change or bubbles when going lock to lock or hitting brakes
 

73azbronco

Contributor
Bronco Guru
Joined
Nov 11, 2007
Messages
8,223
Sounds like air but not squealing. So, try jacking front end up as high as you can, engine off, then slowly turn wheel lock to lock and watch res, any bubbles? Leave it at lock overnight try again next day.

My problem needing hundreds of cycles turned out being one of those inline PS filters, it was holding air. If I put it in after it being bled there would probably not have been an issue. So, It sounds like somewhere you are holding air in the line. Might be bad hydroboost setup, needing rebuild

Have to admit though, if I ever had any small amount of air, it squealed at lock.
 

EPB72

Contributor
Sr. Member
Joined
Jul 13, 2019
Messages
918
Loc.
Pleasant Hill, CA
FWIW, there are hundred thousands of vehicle in OE form that iff you turn the wheel while pushing around.{ meaning a tow in that your moving into the shop} will spit out fluid ,.. so if you let it sit abit after cycling brake pedal, and reapply brakes again lets say 5 min or so does it still overflow?..with engine running does it overflowor is ther ariation in the fluid, the acumilator will remain charged in the event of an engine stall allowing a couple cycles of the pedal with assist , once depleted wondering you get the same result?
 

nvrstuk

Contributor
Just a Bronco driver for over 50 yrs!
Joined
Jul 31, 2001
Messages
9,417
Loc.
PNW
What EPB72 said here " ...the acumilator will remain charged in the event of an engine stall allowing a couple cycles of the pedal with assist , once depleted wondering you get the same result?"

Next Q- with someone closely watching the reservoir level, start the engine,and slowly turn the strg wheel. Does the level drop more than 3/8"? If so, you have trapped air.

In post #9 you mentioned,
"I’m getting no level change or bubbles when going lock to lock or hitting brakes"
Is this with the engine running?



Like Reply
Report
 
OP
OP
S
Joined
Apr 5, 2025
Messages
7
What EPB72 said here " ...the acumilator will remain charged in the event of an engine stall allowing a couple cycles of the pedal with assist , once depleted wondering you get the same result?"

Next Q- with someone closely watching the reservoir level, start the engine,and slowly turn the strg wheel. Does the level drop more than 3/8"? If so, you have trapped air.

In post #9 you mentioned,
"I’m getting no level change or bubbles when going lock to lock or hitting brakes"
Is this with the engine running?



Like Reply
Report
Will try after depletion to see if still overflows. No level change with motor off. I will have wife turn wheels lock with motor running after she home from work.
 
Top