If the hydraulic pump turns on ,it creates pressure , if the pressure is not created then there must be a bad pump .should it be rebuilt or replaced .if not the pump then what is it.thanks

Didn't I answer this yesterday?
Question edited for clarity. Please always include model. Some models have known issues!

Sometimes after a power steering pump is installed, reduced pressure inside the hydraulic lines will build, which can create the symptoms you're experiencing. In other cases, low power steering fluid levels can cause this to occur, as can air bubbles trapped in the hydraulic lines.
Jan 3, 2018

Hard to turn steering wheel after power steering pump replaced

Videos as well

https://www.google.com/search?q=hard+steering+after+changing+steering+pump

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have you inspected the steering rack and pinion. they do wear out and need to be replaced.

Power in a hydraulic system is perceived as Pressure ! there for more power is more pressure , id use a pressure gauge plugged into a remote port , to test your pump . an 85 id bet sure has some wear to pump , pressure for that id suppose should be right about 1200 to 1500 psi at 1050 rpm , if its less than that you could have pump rebuilt or replaced

do ck all the simple things 1st , filter, belts, hoses ,leaks

That is an odd bit of advice. If the oil pump was working poorly enough to cause a noticeable difference on engine performance, then you have already ruined the engine.

Although not always the case, typically if you are losing power as you increase speed, it is a fuel problem. Fuel pump could be going out. Inline fuel filter could be dirty and restricting fuel flow. Intank (gas tank) filter could be clogged and restricting fuel flow.

Regarding your oil pump, you can check to see if it is working correctly by installing an oil pressure gauge. You might check to see if your engine has solid lifters or hydraulic lifters. If it has hydraulic lifters, your engine will develop a tapping noise when the oil pressure is low because the lack of oil pressure creates a lack of hydraulic lift in the lifters and so they collapse creating a gap between the lifter and the rocker arm. This gap means that the rocker arm comes off the lifter and then smacks the lifter when coming back down resulting in the "tapping" noise mentioned.

This is an oil PRESSURE issue, not oil level.
It is likely that when you stop, and the engine returns to idle, the oil pump is not creating enough pressure to push oil up to the top of the engine and lubricate the valve assembly.
I hate being the bearer of bad news, but the plastic impellers in most modern oil pumps do fail over time, especially if they've been disturbed by the work associated with an engine rebuild. Or, it could be that it is not sitting right on the pickup and feed tubes, and they are being blocked and causing pickup problems at low RPMs. The solution will involved dropping the pan to figure out what's going on with the pump.

You have to open any bleeder valve first

Then you slowly push out the air & brake fluid

There is never any pumping to be done on a car
or any product in order to bleed any fluid.

All your doing is getting out the air

Then when the system is closed there is no pumping
to create a high hydraulic pressure ,just a gentle application
of the brake or clutch

Sounds of low oil pressure or oil need changed to thin. Either you need an oil pump or your engine is old and you need to rebuilt it. See the crank and rod bearings create pressure the pump pumps it up. Even if you install a new pump and crank bearing are low. Pressure will be low.

Are you sure the hydraulic motor is bad?....as it's usually a problem with a relay and/or the pressure switch.

LEARNING ABOUT THE "TEVES" BRAKE SYSTEM
The hydraulic brake booster on a late model Mark VII and early Continental is very different from most. It is equipped with something known as a "TEVES" brake system.
The main parts in the system that we will discuss include an ACCUMULATOR, a HYDRAULIC PUMP, a hydraulic pump RELAY, and a PRESSURE SWITCH. These are the key players in this operation.

THE LOCATION OF THESE PARTS ARE AS FOLLOWS:
HYDRAULIC PUMP MOTOR= Underneath the brake assembly (2 pin connector) Hydraulic pump motor
RELAY = On the drivers side strut tower
PRESSURE SWITCH = 5 pin connector facing the # 7 or 8 spark plug(drivers side)
ACCUMULATOR = Round black ball on the drivers side

WHAT THESE ITEMS DO:
HYDRAULIC PUMP MOTOR is an electric hydraulic pump used to "boost" pressure for the brake assembly. This pump is $900 new!
hydraulic pump motor RELAY is just what its sounds like. It gives the hydraulic pump motor power to come on.
PRESSURE SWITCH is the "brains" in the system. It senses how much pressure is "on line", and when the system needs more pressure, it tells the relay to "power up" the hydraulic pump motor.
Another one of its jobs is to turn on the RED BRAKE LIGHT, then the ANTI-LOCK lights to alert the driver that the pressure is dangerously low. (The reason the anti-lock light comes on, is because the ABS cannot function if there's a problem with the manual brakes)
ACCUMULATOR stores energy or pressure like a reservoir. Its there so the hydraulic pump motor only has to come on every 3rd or 5th time. Its design is more complicated, but basically the same principle as an air tank on a compressor.

WHAT NORMALLY HAPPENS:
What usually happens is, in time, the accumulator gets weak with age and can't hold the pressure like it was designed too, and therefore, the hydraulic motor comes on every time the brakes are applied....rather than every 3rd or 5th time. This means all these parts are working 3 or 5 times more than they were designed to. This puts an extreme amount of pressure on an already old system.
What we know from this is, the accumulator needs replacing because it's what started all this, but now the pressure switch and relay needs replacement also because it has worked overworked.
NOTE: always replace the relay when replacing the pressure switch. The relay came on every time the pressure switch told it too, so if one is worn out....the others not far behind!

Does the system pressurize? Check the radiator cap... something as simple as a bad cap can create all kinds of problems. If the system is pressurizing, I would suggest replacing the thermostat again. If it is not installed properly or is defective (this happens more often than it should) it will leave you perplexed until you replace it again. I hope this helps!

check the power steering pump, if its good than it will be rack and pinion issue. the pump create a high pressure to help assist with steering, and the rack and pinion work like hydraulic cylinder which receive the pressure from the pump and the steering work like control valves. by turn left or right you controling the pressure to make the wheels turn either right or left. check and see if you have any leaks.