Hydroboost question
 

2007 F350

I noticed I have a small power steering leak where the master cylinder bolts onto the hydroboost. Is there a o-ring or seal between the two? or do I have to replace the hydroboost?

Been looking online for a schematic but can't seem to find one.

You need to replace the HB.

It could also be a seal in the master cylinder. If the master is leaking it can leak between the two units.

It can, which is more common. I just felt if he says PS fluid, he knows PS fluid.

Book doesn't show a seal between the MC and HB units. Not that the book does always show everything, but for example on fuel injectors it specifically addresses the seals in the Motorxraft seal kit, so if a seal was vital it seems like they'd show it.

The seal is in the HB, and not field serviceable. The area between the M/C and HB is "dry".

The typical failure mode is for the rear sealing cup of the M/C to have a slight brake fluid leak. Then the truck starts to develop dragging brakes with two brakes on an axle or all four brakes at the same time (Not the cause of one wheel brake hangup) due to rust buildup between the HB pushrod and the M/C piston. You can remove the two M/C retaining nuts and pull the M/C forward and it will have rust particles drop out.

If the truck was a vacuum boosted truck the brake fluid would be pulled into the intake manifold or vacuum pump if it was a diesel.

Its without question PS fluid, I have to refill that at least once every month with a bottle. Brake fluid has never changed.

Anyways it comes out on the bottom side of where the two mounting bolts go to mount the MC to HB.

Has anyone used the reman HB? or stick with OEM and new

My money without seeing it is on the master cylinder.

Where does the PS fluid come in contact with the MC?

By "power steering fluid" you mean ATF right?

Sorry, I ozoned when you said PS fluid and had brake fluid in my mind.

Is this a test to see if I know the difference between BF,PS and ATF?


No problem, I asked just in case I had misunderstood how the hydroboost works.

The power steering/hydroboost system on this truck uses ATF and not necessarily stuff from bottles labeled "power steering fluid". If you're adding the green mineral-oil based power steering fluid it's not the correct stuff.

The correct atf is Mercon V.