Was working on my 79 Vette's aluminum mags and I needed to get them outside so I could hose them off. So I fired up the engine and whammmmm, the steering quickly turn hard left. I recognized this as the Power Steering Control Valve out of alignment. I just replaced it and the hoses about 8 weeks ago. So I jacked her up and fiddled until I got it realigned and took it for a ride around the block.

At slower speeds it may have been a bit stiff but as I was bringing back into the garage the steering started shaking heavily. What the heck?

Two Questions:
1) Why did the Power Steering Valve all of a sudden do this? Kind of scarey had I been going at high speed.

2) What does the shaking indicate? I wouldn't want to drive it while this was happening.


Thx for all assistance

Paul

 

There was a very recent thread about a ruptured seal in a power steering ram causing hard steering that might be similar to what you are experiencing. If you recently replaced the control valve it could have failed also. I rebuilt my control valve last winter and it leaked like a sieve when I hooked it up. A seal had torn during assembly. Your control valve may have had a small defect that has gotten worse. The PS system runs under pretty high pressure so any defect is going to show up sooner or later.



Rick B.

 

I found the following statement on the Willcox website as it pertains to replacing the cylinder:

Power Steering Cylinder - New 63-82 SEE PART# 20761 FOR A REBUILT PS CYLINDER. WHEN INITALLY STARTING VEHICAL AFTER CHANGING KEEP HANDS CLEAR OF STEERING WHEEL AS PRESSURE MAY CAUSE WHEEL TO SPIN. See our repair help section on adjusting power steering control valve and cylinder.

 

Yeah, I understand the holding on to the steering wheel.

If you read the details on this site (This is my PSCV) instructions and I am wondering if the surging they speak about is what I am experiencing? I started up the Vette today and turned the wheel and it all of a sudden turned it about 180 degrees. Is this what is meant by surging? Do I need to bleed the lines?

If Steering Wheel Surges, Perform The Following Operation:

Air may become trapped in the power steering cylinder, control valve, or lines, causing surging and require bleeding of the system.
To bleed the system, first place a drain pan or suitable fluid absorbent directly beneath the control valve.

• Loosen the two lines that cross on the end of the control valve approximately 1/8-1/4 turn (counter-clockwise ).

• Start the vehicle while firmly grasping the steering wheel. Turn the steering wheel completely from left to right, while an assistant verifies that a small amount of fluid is spraying out of both lines.

• After turning the wheel from left to right 3 to 4 times, hold the wheel to the right while an assistant tightens the two lines on the end of the control valve.

• Check the power steering fluid level and add as necessary

From:
http://www.mamotorworks.com/corvette...-320-3861.html

 

I think I'd try that before tearing it all apart again. Let us know what you come up with.

 

Dang! Bled it out got it recentered and everything seemed well. Took it for a ride and there was a quick pull to the right and then it started shaking when I turned to the right.

I can't understand what it could be other than the PSCV.

Others?

Paul

 

If your original assist cylinder (ram) had internal leakage and now you have replaced it with a new or rebuilt cylinder with no internal leakage, it is possible that the control valve will need to be rebalanced.

If you can't rebalance the valve, it may need to be replaced.

The power steering system is an "open center" system. In other words the power steering system has continuous flow through the control valve during normal operation with the engine running. It is not like a brake system which is closed. With a brake circuit there is only enough fluid movement back and forth to move the brake piston(s) at each wheel.

Since there is no real flow in a brake circuit, any air in the system needs to be flushed out of the circuit by cracking the brake hoses at each wheel and pumping the brakes.

The power steering system is not like that. The power steering pump continuously moves oil through the system, therefore air is moved up and into the pump reservoir along with the oil with the engine running. Even with the engine off turning the steering wheel from full lock to full lock will also move oil through the system. The reason that it is recommended to turn the steering wheel with the engine off is to prevent air and oil from passing through the power steering pump and getting them whipped to a froth. This will take a lot longer for the millions of tiny air bubbles to seperate from the oil. Since the system is open center it will effectively purge even the foamy oil through normal driving and sitting overnight.

So cracking the hoses at the pump, valve, or power steering gear as a means of removing air is not really a very good procedure.

 

I realize this info appears to come from a reputable source, but this part resonates on my bubba nerve a bit.

Sometimes a procedure is reprinted/passed along without being verified and funny things get through, done for a while, and eventually become practice even though there may be a better way.

I looked through the procedure in my Service Manual and there doesn't seem to be any lines resembling the one quoted here.

 

First, make sure that you have the pump pressure lines and the control valve-to-cylinder lines routed properly; they can be crossed. Next, with wheels off the ground, ignition key to ON (engine off), turn the wheel lock-to-lock at least 8-10 times so that most trapped air is released. Top off the P/S pump fluid, if necessary. Then start the car and balance the steering valve. Follow that with 5 (or so) lock-to-lock cylcles with the engine ON. Recheck valve balancing. If you still have problems, your control valve is installed/built incorrectly [they do that sometimes in China and Mexico and might not test them].

 

I have rebalanced twice. I will attempt the air purge tonight with the manual method described.

My parts dealer is also checking with the rebuilder to see if they have any further advice.

Is there a way to determine if the ram is bad? I have replaced the PSCV and the lines. The ram begins to force the wheels and when held the system shakes.


Thx

Paul

 

If the power cylinder was functioning properly before you worked on the system and you didn't damage it somehow, it should work OK now. There isn't any simple point of failure in that device; it is a sealed unit...it either works or it doesn't, in which case you replace it. Since the cylinder works properly some of the time, I would believe that the problem is NOT with the cylinder but with the control valve.

 

The dealer is shipping me a new one.

Thx for all the tips!


Paul