Maybe I can save you some trouble.
Chances are pretty good the master cyl is original, does not have to be!
Through normal use the sealing cups in the master cyl travel a fixed distance in the bore. Beyond that normal travel distance sediment builds up and the very first time the pedal goes to the floor those cups get scored going over the gritty sediment. Now you have the opportunity for leakage when the brakes are applied. Only you know how many times that pedal went to the floor and repeatedly scored those sealing cups. There is a brake master cyl replacement job in your future, today, tomorrow, but it is coming.
Think about this, if the PS pump is not putting out enough volume and at the right pressure the constant assist for the power steering will not be constant and add to that if the pressure is not sufficient it can't charge the accumulator to the degree to be of any real assistance. As stated by Kyle, there could be an obstruction in the pressure side hose which could produce the same symptoms. I know that PS pump is a dog to get at and replace. The better way to confirm the conclusion is to check the pump pressure with the proper pressure gauge ,and they go over 2000 lbs/sq in hydraulic pressure. You are doing the right thing by trying to get all the info possible and a lot of the simple things often get overlooked.

 

Thanks for the info.

 

This is Ford Reman, they do not sell brand new ones from Ford anymore but the reman comes with the Ford 2yr/unlimited mileage warranty. Also, there is a $40.00 core on the part... Let me know if you need any diagrams, I would be happy to post them.

 

Have you checked the belt tensioner for being frozen in which case it might permit the belt to slip producing erratic performance. One of those simple things !

 

You were spot on with this one. Looks like the master cylinder was the culprit. Brakes are no longer squishy. I have a new issue now. I ordered the master cylinder "BRMC-28". My old master cylinder had a sensor on the end "f3ta-9f924-ca". The new cylinder has no tap for it. I am reading that the sensor was recalled, and should be replaced with "1L1Z-9G652-AA". What should I do since I have no mounting? I assume my cruise will not work without one plugged in and mounted on the cylinder. Any way to get around that? Looks like the master cyliner I should have ordered was 5C3Z-2140-LB

 

There is an old manual switch mounted near my steering wheel on my truck that a previous owner used for his CB radio. I already pulled the wires from it, but I think I will use it to toggle the master cylinder cruise control cut off sensor manually. The cruise will not work without the sensor plugged in, but I read you can jumper the plug since the system runs normally on a hot signal. The problem with just using a jumper is you are only left with 2 of the 3 sources to kill the cruise. The off button on the steering wheel, and a signal it gets from the tail lights. My off switch on the wheel never worked and I've never tried to find out why, but I would assume if your bulbs went out while cruise on, a faulty steering wheel switch, and a jumper in the cruise cut off master cylinder sensor pigtail, you would essentially be stuck in cruise. A kill switch adds safety. The best solution is buying the right master cylinder, but I dont want to be buy another and have to redo my work. The new sensor comes with an additional wiring harness that is fused, so I will fuse my switch also just to be safe. However, I think with appropriate wiring and shielding, even with a fluid leak, mine should never short.

 

If you post the VIN or send it to me in a message I can verify which master cylinder your vehicle calls for.