Oh my gosh how can things be so complicated!!

My 78's control valve was leaking and I purchased one from Blair's and installed it. After that I had no power assist. They shipped me a new valve today and I cleaned the pressure valve in the pump (twice) and centered the new (second) valve....and still no power assist. I can see inside the pump's pressure valve and it looks fine plus I can hear the small ball rattling in it. It also move inside the pump bore pretty freely.

When I disconnect the high pressure hose from the control valve fluid comes out- it runs out but does not spray out as if its under a lot of pressure. However, I am not sure how much pressure it should have.

The strange thing is that if I turn the wheel to full lock in either way the pump does not make a sound.

Guys- I need help. I am now down to replacing the pump to see if that fixes it. Does it nake sense for a pump to go bad as quickly as it did?

Any help is appreciated !!
Dan

 

that may fix it, I'm sorry for your problem , its an all to common complaint with these cars and unfortunately nobody , including my self, seems to have a good diagnostic to follow. I have seen threads where two and three ps valves were swapped before finding one that worked . best of luck

 

You should not be able to hear a ball rattling inside the flow control valve assembly. The ball should be spring loaded so that it controls the maximum pressure that the pump produces. I tried to find a good blowup or cutaway drawing of the valve assembly. No luck so far. Here is a verbal description.

The hex fitting with the screen built into its face screws into the flow control valve body. A small ball bearing should be seated (pressing) against the underside of the hex fitting. The ball should have a small pilot pin and then a spring preloading the pin and ball against the hex fitting.

Early flow control valve assemblies had one or more shims under the head of the hex fitting. Added shims moved the hex fitting away from the spring loaded ball bearing and reduced the relief pressure. Less shims (or no shims) would compress the spring more, increasing the pressure relief.

If you can hear the ball rattling, it is not performing its pressure relief function and the pump cannot build any pressure.

One last comment, the C2/C3 Corvette has a flow control valve assembly that allows only 950 psi relief pressure. Most GM passenger car and truck power steering systems utilize pressures as high as 1400 psi. The small hoses on the Corvette power steering system will not withstand those 1400 psi pressures. Although there are millions of old Saginaw power steering pumps in salvage yards, you cannot just grab any old flow control valve from just any GM pump and slap it into your Corvette pump. It will most likely be set at a higher relief pressure and cause your hoses to leak.

I might try and contact a pump rebuilder like Cardone (I am sure that there are others) and request that you purchase a GM P-pump, power steering pump flow control valve with a 950 psi pressure setting. I would hope that you can find someone that would sell you that internal GM pump part.

You might contact Tom Lee of Lee manufacturing in California.
(818) 768-0371 He specializes in complete power steering systems and most likely could provide that special flow control valve with the correct 950 psi pressure relief setting.

Also Jeff Roethlisberger of Turn One here in Saginaw, Michigan might be able to supply the special part as well. (989) 759-4206.

The one thing that really bothers me is that in your description of the problem, there is no indication as to someone (Bubba) taking the flow control valve apart and losing the spring and/or pilot pin. I guess that the spring itself could fatigue and break causing the ball to be loose inside the valve assembly.

Good luck,
Jim

 

Well I think I won the battle

I replaced the pump and that solved it. I still have no idea how a power steering pump can go so bad with zero warning. It worked before I changed the control valve and did not afterwards.

I drained the fluid so many times (to change components) the power steering fluid is cleaner that it was in 1978 when it rolled off the assembly line.

Thanks to all who helped- especially Jim Shea. I took your advice and contacted Jeff at Turn One and he was very helpful. Its strange that the steering was dead at any rpm. I then switched out the pump relief valve and had a little bit of steering assist and higher rpms and then finally solved it with a new pump. He gave me several ideas.

Thank goodness that's over!

Dan