[Mr. G]

The P/S went out on the '71 and was curious if rebuilding it using a Gates rebuild kit will remedy the issue with it or does the entire pump need to be replaced. the pump is spinning but when the wheel is turned lock to lock, power steering fluid is pushed out from the cap on the pump. Never had one of these give it up before so I don't know if a rebuild is possible without some special tools or something. Thanks.

[OG68]

Pressure relief valve might be stuck.
Remove the discharge line and fitting and verify relief valve is free to move. If you can't feel it with your finger it's more than likely jammed forward. The valve is spring loaded so insert a small brass drift pin and lightly tap it with your palm or ball peen hammer to 'pop' the valve loose.

https://benchworksteering.com/blogs/tech-talk

[Mr. G]

Thanks for the info. I will give that a try and report back.

[Mr. G]

Yes. The pressure relief valve was stuck alright. A couple taps with the drift and out it came. Excellent call on your part and the link was very helpful also as although I thought I knew how to bleed the PS, i was not exactly right. Great info for a guy who didn't know much about PS pumps. THANK YOU!

[Mr. G]

Well upon re-assembly and then testing, the power steering still does not work. Makes a knocking sound when turned to the right but not to the left. The rebuild kits look to have just seals and O rings and a bushing. I don't know if any of those items going bad would cause the pump to fail?

[OG68]

The relief valve moves back and forth inside the bore all the time. So it's possible after 50 some years the bore may be worn to the point that the valve is getting cocked. You can buy the pump separately and with a seal kit replace it keeping the original reservoir.
Or
There may be dirt in your system causing the problem. You may want to consider a return line filter after flushing.

I went through the same thing with my El Camino. What I found was a few dog hairs (German Shepard) in the bore. Also discovered she liked to sleep under the radiator. The lower A/C condenser was matted with dog hair. Evidently a few found their way into the PS when refilling
After cleaning under the car, radiator and condenser and thoroughly flushing the PS the problem went away.
Strange but true.


Jim Shea, a retired Saginaw engineer wrote 'The Steering Papers' one of which describe how to bleed air out of the system.

The steering papers original domain has expired but can be downloaded here. warning; Very large file.

https://archive.org/details/corvettefaq

POWER STEERING SYSTEM DEAIREATION

You may already have read the GM bulletin on removing trapped air from a power steering system. This paper is written to complement the GM procedure and add just a bit more detail on the subject. By the way, I really don’t think that “deaireation” is a real word. But it was created as part of our engineering culture at Saginaw Steering Gear Division to describe the elimination of the trapped air.

Some people think that the power steering pump must be spinning (with the engine running) in order to circulate power steering fluid and drive the air out of a freshly repaired or assembled system. This is really not the case and actually can cause a real lengthening of the time required to “get the air out.”

When you start your engine and begin spinning the power steering pump any air that is trapped in the system begins circulating throughout the pump, gear, and hoses along with the power steering fluid. When large bubbles of air pass into the pumping area of the power steering pump the air and fluid get whipped to a froth as they engage the spinning rotor and vanes. The results will be a milky colored mixture of entrained air and oil that is now being pumped through the system. The mixture takes up more room (and expands far more as the fluid heats up) than pure fluid. So many times you will find that suddenly you reservoir is overflowing. You have also created a somewhat compressible fluid (because of the many, tiny, air bubbles.) This can now cause erratic power assist.

Once the fluid is filled with entrained air, it will now take quite a while for the very small air bubbles to come out of suspension from the fluid and make their way as larger air bubbles into the pump reservoir. You will note that the pump reservoir is typically the highest point in the hydraulic system. Left on its own, air will eventually rise into it and escape to atmosphere. However, this fluid action may actually take a several days.

There are two generally accepted methods of eliminating air from a power steering system. One is to pull a vacuum directly on the reservoir and then start the engine. A vacuum at that point will literally suck the very small air bubbles right out of suspension as the circulating fluid passes through the reservoir. This procedure requires a special “stopper” to fit the fill neck of the reservoir. The stopper will have a hose connection and is connected to a means of drawing a vacuum. This procedure works very well but requires special tools.

Please note that this procedure can sometimes fail because a worn seal can allow continual seepage of air in the pump driveshaft area or in several sealing areas of the steering gear because of the high system vacuum. The pump will then continue to create froth as the newly entering air passes through it.



The other method is to eliminate the majority of the air BEFORE starting the engine. First jack both front wheels off the ground. (Make sure that your jacks have clearance when the road wheels are turned to full lock.) With the engine off you can rotate the steering wheel back and forth (full lock to full lock) and the rack piston inside the steering gear will act as a pump. Rotating the steering wheel will gently move the fluid along with any large air bubbles through the circuit until the air can rise directly into the pump reservoir - and out. It is a good idea to hold the steering wheel at full lock for about 5 seconds each time before turning in the opposite direction. This allows the air to rise into the pump reservoir with each steering cycle.

Refill the pump reservoir to the COLD mark on the capstick and rotate the steering wheel lock to lock many times again. This should get MOST of the air out. Then drop the car back down and start the engine. Try a few more lock to locks but now be sure NOT to hold the steering at full lock for more than just a few seconds. Recheck the fluid level and fill if required. Go for a 10 mile drive.

One last tip, I recommend that you use genuine GM power steering fluid that is available from GM dealerships. I don't recommend using the stuff that is labeled, "Meets everyone’s specifications." The only fluid that has been tested in tens of thousands of Saginaw laboratory tests and millions of vehicle test miles is the GM fluid. Also the GM fluid is pretty good at dispersing the air out of fluid suspension.

I hope that you enjoyed this brief dissertation.

Jim Shea
JIML82@aol.com
DeaireationJimSheaProcedureRev25JA07.doc



[Mr. G]

Wow. I never thought about PS in such depth. This has been truly enlightening. The valve does feel sloppy in the bore when depressing it. I did not realize that there is a fine screen at the deep end of the valve and I took a pointy screw driver to clear the gunk away that was there and found out about the screen after poking a hole in it. I think maybe a new pump is in order. I also appreciate the fluid recommendation as that was one of my next questions. Any good sources for a new pump? Thanks for all the help. I am quite surprised with myself after all these years of messing with these cars and I am absolutely clueless on the PS system.