Hello! Long story short, a few month ago I noticed a hum when I pressed my brakes or turned my steering wheel. I'm in a 2001 F250 Ext Cab 7.3L 4x4. I bled the hydroboost and removed the old fluid and refilled with some Merc. Truck drove fine for a long time and hum was quietened down a good bit. A few weeks ago I was driving home and my brake pedal went to the floor. I pulled into a parking lot and noticed steering was tight. Power steering reservior was pretty dry so I added some and limped home. Since I got home I have bled the brakes and now the hydroboost 2 times. The power steering works and the brakes work, but not both at the same time. If I hold the pedal down it does have stiffness, but while holding it down, I can't turn the steering wheel. If I turn the steering wheel and hit the brakes, the pedal goes to the floor. The hum is silent until you turn the wheel to the far right or left. Any suggestions here? Thanks in advance!

 

If hydroboost was defective it should not affect power steering.
If PS pump is defective will affect both steering and hydroboost.
If possible try to stay with new OEM PS pump.
Find reason pump went dry !

 

Agreed!!

 

Agree with Hanky, it may be a hose and not necessarily the pump. If you end up needing a power steering pump the part number is likely F1TZ3A674DBRM and we have it available here: #F1TZ3A674DBRM: P/S pump. I would be happy to double check the fitment of that part if you send me your VIN.

 

I did some further testing. Before I start the truck, the pedal goes down all the way faily easy, but does return also. No matter how many times I press it, this always happens.


I found a trouble shooting guide here: | Repair Guides | Brake System | Hydro-boost (hydraulic Boost) | AutoZone.com


So I began the Hydro boost test:
Vehicle in neutral and engine off, I pressed the pedal all the way down 5 times
While holding down the 5th press, I started the engine
The pedal did drop but then kicked back up and was firm.
That should confirm that the hydro boost is good


Took the truck around the block since pedal was firm, but everytime I went to slow down, usually while making a turn, the pedal was going to the floor. Power steering was working great though.


After parking, using the guide mentioned above, next was the accumulator test
While running the truck at idle, I turned the wheel to the stop and help it there for a few seconds
Then returned it to center and turned off the engine
When I pressed the brake, the pedal went all the way to the floor
When I started the engine and repeated to turn the wheel to the stop, I never heard a hissing sound while I was in the cab with the hood up and door open, but maybe with 2 people I could.


After stopping the engine, I think I should have gotten atleast one power assisted brake according to the guide, but I got nothing.


I am thinking the accumulator may not be filling or its leaking out the air(?) immediately.


After running the last test I sat in the cab and turned the wheels a few times with the truck running. For the most part the steering felt normal, but sometimes it would be a little more difficult. After turning the wheels and pressing the brakes softly but quickly I would fill a slight dip and then kick back from the hydroboost.


Any one got any recommendations?

 

You are overlooking an important item and that is where did the fluid go that you had to replace ? If the pump ran dry it could be running on borrowed time.

 

I wish I knew. I checked it a few minutes ago after flushing it 2 days ago and still had good levels. I havent noticed any leaks around the truck but I'll put something under it and check again.

 

You could also have a hydraulic brake system problem where the master cyl will not hold pressure.

 

I was wondering if maybe the master cylinder could be the culprit also. It just seems odd that the brakes bleed fine from the calipers and I have a good stiff pedal when I'm idling and not turning the the wheel. I am going to look up some info on trouble shooting the master cylinder, check my hoses then go from there on the repair. Thanks for your input so far. Hope to get this hammered out soon.

 

Thats a really good price. Thats new, not reman? Is there a core charge?