Loss of Power steering when applying brakes with Hydroboost

[C8Bronco]

I recently bought a 74 Bronco that had a lot of work done but never completed. I'm able to drive it now and when applying the brakes I loose most of the power steering. I'm not sure if it's plumbed properly. I tried to identify the brand of the hydroboost but I haven't had any luck. Other than when braking the power steering works fine. Fluid is filled to where it should be. Attached are a few pics. Any help would be appreciated.

 

[toddz69]

Hard to know exactly what hydroboost it is. My guess, if it's not plumbed incorrectly, is that the pump is failing. Many Ford Super Duty owners used to complain about the same symptoms with their trucks.

Todd Z.

 

[pcf_mark]

Does it make a lot of noise too? If so you may have air trapped. That took some time for me to get it all out and while I had air I had underwhelming brakes or steering.

I put the wheels in the air and kept cycling it back and forth slowly trying not to hit the stops.

 

[C8Bronco]

Does it make a lot of noise too? If so you may have air trapped. That took some time for me to get it all out and while I had air I had underwhelming brakes or steering.

I put the wheels in the air and kept cycling it back and forth slowly trying not to hit the stops.

There's no excessive noise coming from the PS pump and the fluid looks nice and clear. I can literally start it up and start turning the wheel very slightly and it's fine but as soon as I apply pressure to the brake petal the steering stiffens right up.

 

[DirtDonk]

Is it a dual return pump? Or is there a T-fitting in the return line?
I remember hearing lots of horror stories about t-fittings versus Y-fittings, causing some issues.
Kind of looks like a dual return from here, but I wasn’t sure.

What about hose sizes? Are all the feed and return hoses the same diameter? Anything that could be causing a restriction? Such as a sharp bend or kink in a hose?
How old is the installation? I wonder if something is deteriorating internally and can’t be seen.

 

[904Bronco]

Generic picture attached...
If lines are hooked up correctly, then I would suggest a pressure gauge on the PS pump discharge. (to rule out weak pressures) On that, the Explorer pump issues I had were related to a stuck wide open pressure valve on the pump.

The "T" situation that Paul speaks of is a concern, can't really tell From you pictures if that is present or if you have a dual return pump.

 

[pcf_mark]

I would depress the brakes a lot to be sure they are bled. If it is a T return line (I have one) then the top/hoirzontal part of the T should be return from p/s box on one side then other side of T should go back to the reservoir. The vertical part of the T is for brakes because the volume is so little.

 

[Apogee]

The HB unit should only use a few tablespoons worth of fluid when you apply the brakes, otherwise the high-pressure power steering fluid should just travel through the unit and to the steering gearbox. That fluid is typically released from the power piston bore when you release the brakes, so the only time you should have fluid entering the return line from the HB unit would be when you release the brakes, and it should be a small amount. I would disconnect the return line from the HB and feed it into a bottle, plug wherever it currently connects (tee fitting or dual return pump), start the engine and have someone apply and release the brakes. If you're seeing any sort of steady stream of fluid out the return when the brakes are applied, then it's time to rebuild the HB unit.

My understanding is that the steering gets heavy/hard when you apply the brakes, but how well do the brakes work?

 

[cbunas]

Can't really tell from your pictures if you have a dual return or some sort of T fitting. You need a dedicated return from the HB back to the reservoir.

 

[Yeller]

It is very clear that he has a dual return pump saginaw pump, so the T suggestions is not the issue. My guess would be air in the system somewhere, but I personally have never experienced this issue so I'm at a loss as to the cause.