PS fluid overflowing out of reservoir

[InspectahDEck]

Just starting the other day, if I depress the brake pedal while vehicle is off, fluid will come spilling out of the reservoir, with the reservoir cap still on. Problem does not happen while vehicle is running. It is not overfilled, the fluid level goes very low after spilling out as quite a lot will come out. This is on an 05 yukon, any ideas?

 

[Joseph Garcia]

Power steering fluid or brake fluid?

 

[InspectahDEck]

Power steering fluid. It spills out the edges of the Power steering pump resevoir cap

 

[Doubeleive]

Power steering fluid. It spills out the edges of the Power steering pump resevoir cap

sounds like some kind of stuck valve, must have hydroboost brakes?

 

[exp500]

Another possibility is an air leak on the suction side of pump. Usually loose hose.

 

[InspectahDEck]

Yes I did replace the hydroboost maybe 6 months ago due to a leak from the weephole. Brakes feel normal however when driving

 

[Donal]

Yes I did replace the hydroboost maybe 6 months ago due to a leak from the weephole. Brakes feel normal however when driving

sounds like the accumulator spool valve is malfuncting. Does the booster have a limited life time warranty?

Accumulator leak down test:
1. Start the engine and charge the accumulator by turning the steering wheel stop to stop.
2. Turn engine off and let vehicle sit for one hour.
3. After one hour there should be at least two power asisted appication of brake pedal with engine off.
4. If the accumulator will not hold a charge for one hour, but functions normally after charging, the accumulator valves are faulty.
5. If the accumulator has lost its gas charge, the accumulator can will rotate and be loose.

The over flow conditions may indicate the accumulator spool valve is releasing the stored energy and pushing the fluid back into the resivour with one brake pedal application.