Power Steering Flow Valve - Chevelle Tech
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post #1 of 5 (permalink) Old Aug 15th, 07, 5:18 PM Thread Starter
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Location: Melbourne, FL
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Power Steering Flow Valve

My 65 Chevelle has power steering that has never worked since I bought the car. The power steering never has power, and the fluid would eventually drain out - even though all the hoses and fittings were tight and not leaking. A local mechanic eventually told me that I need a "check valve" between the pump and the reservoir that was a part that was typically forgotten when someone would replace the stock reservoir. That was what he thought was wrong with the power steering system.

My car came with a new (well, non-stock) reservoir, and I have no idea about this "check valve". I assume he means the flow control valve which is the closest thing I could come up with when searching the forums here.

My questions (in no particular order):

1) Is it possible to buy a new valve for my 1965 power steering pump, and if so, where?

2) Is the check valve that this guy is talking about actually a flow control valve?

3) Is there a "generic" valve that will have the correct flow rate or will I need something specific to my car? Do GM cars share valves, so one from another model might work?

Thanks guys!
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post #2 of 5 (permalink) Old Aug 16th, 07, 9:15 AM
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Re: Power Steering Flow Valve

Do you have a small block or a big block? It makes a lot of difference with respect to the reservoir. (BB have a remote reservoir.)

Have you or someone been driving the car with the pump empty? You may have ruined the pump because power steering fluid is required to lubricate the rotating pump parts.

Here is how to check for the flow control valve that is inside your pump. You should be able to disconnect the pressure hose from the back of your pump. Then unscrew the fitting with the 1 inch hex from the back of the pump. Right behind the fitting (inside the pump) should be the flow control valve. That valve should have a small spring behind it. That spring should be pushing the valve toward you. You can use a small magnet to draw the flow control valve out of the pump bore.



Even if the "flow control" valve is missing, you still need to determine where your system has a leak.

My gut feeling is that you should just purchase a rebuilt pump.

JIML82
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post #3 of 5 (permalink) Old Aug 16th, 07, 4:59 PM Thread Starter
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Re: Power Steering Flow Valve

The pump is on a small block engine. I haven't been driving the car much at all, it's been in a constant state of restoration since 2002 when I purchased it and I haven't done much more than to start the car to tune it and drive it the 10 feet back and forth from where it is parked to where it gets worked on. I can't speak for what the previous owners did with it, but they had done a good hack job on most of the rest of the car...

I figured I may just need to get a new pump but I was first trying to decipher what the mechanic was talking about. Thanks for clearing it up!

If the valve is missing, is there a way to get a new one to test out the system? I can't seem to locate one from the resto houses or even a standard parts store, but then I am not really sure what I am looking for.
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post #4 of 5 (permalink) Old Aug 16th, 07, 8:37 PM
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Re: Power Steering Flow Valve

There are millions of them just sitting in salvage yards right inside the Saginaw pump and behind the discharge fitting. I am quite sure that the valve has kept the same shape and dimensions over the last 40 years. Even though your pump has a male discharge fitting, the flow control valve has remained the same.

Now the maximum pressure that your pump can develope is controlled by this same flow control valve. The side of the valve that faces forward (toward the pump pulley) has a small hex head screw. Modern flow control valves have a fine mesh screen in the face of this hex head screw (I don't know if they had screens back in 1964). That hex head screw will have shims underneath the head. This is what sets the relief pressure of the pump.

Chevelle pumps back in 1964 only developed about 900 psi. Most modern GM pumps now develope 1400 psi. Now you only develope this kind of pressure when you have the steering wheel cramped at a full lock turn. But be aware that if you have 40 year old hoses and gear seals in your car, they may not like this sudden 50% increase in pressure.

Also the modern flow control valves have the pressure setting secured by epoxy on the hex head screw threads - not shims. If you can turn the hex head screw, I would try and unscrew it by 1/3 of a turn or so. Then add some new loctite to the threads. I don't know what your new relief pressure will be, but it won't be 1400 psi!

JIML82
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post #5 of 5 (permalink) Old Aug 16th, 07, 10:00 PM Thread Starter
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Re: Power Steering Flow Valve

Thanks Jim, that helps me out a lot. I'll keep you posted on how the situation turns out and if I go with the flow valve hunt or just get a new pump.
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