Power Steering Fluid, I'm confused

[Greg S.]

I rebuilt the power steering pump for my 75 corvette thinking I'll get some more of the red gm power steering fluid to refill the pump. Went to my FLAP store and got some Lucas fluid for GM type pump. It is clear. Thought maybe I ought to get some GM issue since I am mixing with the old red fluid in the ram. Went to Chevy dealer and they gave me Delco 10-5043 12345866 which is labeled as good for cold temps. It appears green. Is it OK to mix either of these with the red stuff?

[Mark E.]

Re: Power Steering Fluid, I'm confused

I recommend two things:

- Flush your complete PS system to remove any old fluid. I don't know why you rebuilt the pump, but if it failed there's a chance your remaining fluid is contaminated, hence the need to flush. While the low pressure hose is disconnected for the flush, check for an in-line screen/filter that is often added; if it's there, replace it. When refilled, you end up with all fresh fluid of one type, which is a good thing.

- Any quality brand of PS fluid that meets your car's specs will work fine. Whatever fluid you choose, be sure it meets the specs shown in the owners manual. And remember PS fluid is different than ATF.

After I rebuilt my PS system (pump, cylinder, valve, hoses) I used Red Line's synthetic PS fluid, which met my car's specs. The system operates smoothly and quietly.

EDIT: Be sure to properly bleed the system to prevent damage to your new pump. The procedures for flushing and bleeding are in the service manual.

[Greg S.]

Re: Power Steering Fluid, I'm confused

I removed a rebuilt pump that was operating fine but leaking from the return hose. I had the pump original to the car so I rebuilt and installed it. How is the system flushed.

[Mark E.]

Re: Power Steering Fluid, I'm confused

It helps to have two people to do this but you can do it yourself if you pay attention to the fluid level in the pump tank and shut the engine off quickly when you need to open a new bottle (or have them already open). It will take almost 2 quarts to completely fill the system so get 4 for the flush procedure.

- Raise the car so the front tires are off the ground.

- Remove the return line from the back of the PS pump and extend the hose (using clear tubing if possible so you can see the color change). Make the hose long enough to go to into the container to capture the fluid. A gallon milk jug works great. You want to see the fluid coming out WHILE you are pouring it in. You don't want to have to stop pouring for any length of time while you check the color.

- BLOCK THE RETURN PORT TO THE TANK ON THE POWER STEERING. A short stub of hose with a bolt in it works. Otherwise fluid will pour out as you fill the tank.

- If you have a new or rebuilt pump (like you do), fill the pump with new fluid and then spin the pulley by hand to prime and lubricate it. This prevents a dry start.

- Open 2-3 more quarts of fluid and have them ready.

- Start the engine and start pouring fluid into the PS pump at a rate necessary to keep the level up near the top. You don't want to starve the pump of fluid. It doesn't come out really fast so you can easily keep up. If you have to stop, just shut off the engine and add fluid to the tank before you restart. Shutting the engine off quickly is the role of your helper; otherwise just be quick on your feet. There's a small chance the steering will jerk left or right so keep your hands away from the steering wheel.

- When you see the fluid color change in the tubing, run about another pint through and then shut off the engine.

- Reconnect the line to the tank. You may choose to add an aftermarket screen/filter inside the return line.

- Top off the fluid. If you need to remove some, a turkey baster works well.

- Start the engine and then turn the wheels left and right ALMOST to the stops but don't go to them. Do that 10 times or until you no longer see air foaming from the fluid. Odds are you won't have any air but this helps get any out.

- Shut the engine off and let it stand for 10 minutes.

- Recheck the fluid level and add or remove if necessary.

- Restart the engine, let it warm up and recheck the level.

The next step is to balance the PS valve. That procedure is also in the service manual.

[Jim S.]

Re: Power Steering Fluid, I'm confused

I have two comments concerning power steering fluid and a procedure for "getting the air out."

1. GM power steering fluid is the only fluid that is specifically formulated to operate with the GM power steering pump. Other fluids may state that they meet power steering specs but those fluids were not tested and certified on GM vehicles with GM power steering systems for millions of test miles and thousands upon thousands of laboratory durability tests.
GM 89020661
AC Delco 89021182

2. I agree Mark's procedure for flushing the power steering system. However, I have found that you do not want to start your engine to push air out of your system. With the front wheels off the ground, it is very easy to rotate your steering wheel from full lock to full lock. This allows the assist cylinder (on a C2/C3 Corvette) to act as a pump and push fluid and air in and out of the system. This procedure works with introducing new fluid into an empty system as well.

The problem with starting the engine is that air and oil circulate through the spinning pump and the air and oil are whipped to a milky froth. Now with millions of tiny air bubbles now suspended in the fluid it may take a day or two to get them to recombine into larger air bubbles. With the front wheels off the ground (engine off) and the steering wheel rotated you should add fluid to the pump reservoir. As you refill the reservoir you should also see large bubbles coming to the surface of the the fluid in the reservoir.

Jim