I have 1974 corvette with power steering. Installed new pump, control valve and cylinder but having a problem.

1. Hard to adjust control valve. There is so small room for adjustment. in about a quarter turn of nut on the control valve, the cylinder rod changes it's moving direction. I can barely adjust it to keep staying. Even if it is adjusted and the piston does not move, I can not move it by finger.

2. Once it's adjusted, within few days, the wheel starts to slowly turn by itself when engine is running. (to the right side)

I instantly thought I got a defective control valve. So got it replaced with another one. But the problem is still there.
So I am wondering, if the cylinder is defective.
Can a bad cylinder cause this kind of problem?

Just in case someone questions the hose installation, this is how I did. I am sure it is done right.





Thanks.

The cylinder only does what the control valve tells it to do. I always adjust mine on the side of the road using a 1/4" drive 7/16" socket, a 6" extension, and a 1/4" ratchet or breaker bar. I'll drive down the exact center of the road when no traffic is present then make tiny adjustments until it'll track dead straight.

Just before I make an adjustment I'll turn the wheels all the way to the right to move the valve up close to me. After getting it adjusted make sure to put the dust cap back on after you get back home.

Thanks. But my problem is that the control valve comes out of balance by itself even if the lock nut is new.

Try marking your adjustment nut to check for movement, nut is not designed for excessive turning

That's not right. I recently rebuilt my control valve and installed a new cylinder. The adjusting nut had a "null zone" of about 1/2 turn. Within that window, the shaft of the cylinder didn't move. I set it to the approximate center, and it's been fine.

I don't know how the problem you're describing could be the cylinder, but if you've replaced the valve twice...

What was the original problem with the system?

The original problem was leaking fluid from everywhere. I am suspecting cylinder because those two valves I tried showing the exact same pattern of problem. very narrow adjusting zone - 1/4 turn and comes out of balance few days later by itself.

Just thinking out loud here... Could too much pump pressure could cause this? Would that make the control valve over-sensitive? Unfortunately, I'm not at all an expert on the inner workings of these particular parts. Maybe someone else will jump in.

When you are adjusting the valve.. are you taking the cylinder off the frame bracket?
If you are not, try following the instructions on the pdf and you should get it right.

http://repairs.willcoxcorvette.com/w...adjustment.pdf

Install valve in vehicle.
Connect all hoses and fill the pump reservoir with oil.
Do not connect the piston rod to the frame bracket.
If the car already has a valve on it and you are just trying to balance it, remove the piston rod from the frame bracket and proceed.
To get to the valve adjusting nut, remove the press on cap on end of the valve shown in the picture below


2. With the front wheels elevated, start the engine. One of the
following two conditions will exist:

A. The piston (power steering cylinder) rod will remain retracted. If this happens, turn the adjusting nut clockwise until the rod begins to move out. Then turn the nut counter clockwise until the rod just begins to move in. Now turn the nut clockwise to exactly one-half the rotation needed to change the direction of the piston rod movement.

B. The piston (power steering cylinder) rod extends upon starting the pump, move the nut counterclockwise until the rod begins to retract, then clockwise until the rod begins to move
out again. Now position the rod to exactly one-half the rotation needed to change the direction of the piston rod movement.

CAUTION: Do not turn the nut back and forth more than is absolutely necessary to balance the valve.

3. With the valve balanced, it should be possible to move the cylinder rod in and out manually.
4. Turn off the engine and connect the cylinder rod to the frame bracket.
5. Restart the engine by reaching around the steering wheel. If you reach in the wheel and the valve is out of balance the steering wheel will turn hard and can hurt your arm. If the front wheels (still elevated) do not turn in either direction from center the valve has been properly balanced. If not, correct the valve adjustment if necessary.
6. When the valve is properly adjusted, grease end of valve and install the dust cap.

Note: You can adjust the power steering control valve with the power steering cylinder rod connected to the car. This is not advised unless you have replaced all suspension parts in the
front end of the car. If the suspension is old, you should only do this at your own discretion.
Adjusting the power steering control valve with the cylinder rod attached will balance the valve to the car. Any misaligned or defective parts will cause the valve to adjust properly with the wheels elevated, but the car will not steer properly if you have any defective or worn parts. (An example of this would be a defective tie rod end, idler arm, and or worn valve stud).

That is the procedure I followed. I balanced the valve without connecting the cylinder rod to the bracket. But when balanced I can't move the piston rod by hand.

You won't be able to move the rod by hand... The rod should move inward and outward with the turn of the nut under the cap... There is usually about 1/2 a turn +/- either direction where the rod will not respond to the nut being turned.

Possibly something was in the fluid and blocking the line or something. Have you tried to re-balance it again? It could be that you had a bad valve but two in row would be very odd but then you are getting aftermarket valves too.

It pretty much can't be the pump... because the rod is the servant to the valve only and if the rod is moving either way it's getting pressure.

Willcox.