Hydroboost is a system where the power steering system is used to power the brake booster. SureTrack community member Ourfamilygarage had a Ford Super Duty truck in the shop that had spongy brakes and the steering locking up while braking. They posed the question to the community, and with the help of fellow community member juniur and others, they were able to resolve the issue quickly.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
2009 Ford Pickup F250 Super Duty 6.4L
Spongy brakes, hard steering when braking, rerouted hydroboost lines.
Customer complains of spongy brakes.
Diagnostic Steps Performed/Parts Replaced
Road tested truck and noticed the steering locks up as you brake and is much easier to turn once you let off the brakes. Customer replaced master and booster and no change. I’m thinking the power steering pump is getting weak since this is a hydro boost system. Power steering fluid is full but looks a little dark. When pressing the brakes hard enough to get them to actually stop the truck (almost to the floor) can hear hissing in the cab from the booster sounds like a vacuum booster leaking but this is hydro boost could customer have put in a bad booster? He started with spongy brakes before changing master and booster. Pump builds 1800 psi when deadhead valve is closed on tester. Is there anyway to verify the steering gear control valve is leaking other than replacing the steering gear? Or is there any possibility that there’s air in the brake system from the customer swapping the master cylinder causing hydroboost issues?
Best Answer from Community Member juniur
Hydroboost will do some funny things is the power steering hydraulic pressure is too low.
Previous shop that replaced something in hydroboost system hooked the pressure and return lines up backwards on the booster causing the weird issue.
Rerouted pressure and return lines on booster, brakes and steering now work correctly.
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