How to drain power steering fluid?

[Stefan]

My car is a 1999 Boxster 5-speed with a 1999 3.4L 996 engine.

The power steering fluid level is stable but the power steering hums constantly when the car is running (idling or not, turning the wheel or not). There doesn't appear to be any leak and the fluid level is correct.

I figured that before I do something radical like replace the PS pump that I would try replacing all of the fluid. I tried a strategy suggested by one board member, which was to siphon off the fluid from the reservoir and replace it with fresh fluid. I did that several times over a period of months but the power steering noise is still there and is quite loud.

Is there some way I can replace all of the fluid at once, perhaps by disconnecting one or more power steering line at the bottom of the car and letting the fluid all flow (or drip) out?

[RFM]

I would check both power steer lines ( from the pump to the steering rack ) first for damage ( crushed ), it's not the first time someone destroyed the lines while changing out the engine.

[JP Rodkey]

You gotta isolate the noise. If it coming from the front, it's a problem with the rack (assuming there is no trapped air, and it doesn't sound like there is based on what you wrote). Only solution for the rack is replacement or rebuild. If the noise is coming from the pump, changing out fluid is not likely to solve that, either. If pump is noisy and the level is up to spec, then replace the pump.

To throroughly drain the system, remove the underbody panel just below the driver seat (long black phenolic with a bunch of plastic nuts) and disconnect the pressure line union. Easy to see and convenient for draining. If you want to be really thorough, you should also remove the hose clamp/hose on the return line hidden behind the inner frame gusset on the driver's side - just under/ahead of the intake air box. The pump and reservoir will drain naturally, as will the rack. You can move the steering wheel back and forth to push out the fluid. Alternatively, you can loosen the drive belt and rotate the pump pulley by hand to make sure you've cleared out the fluid and see if you feel anything abnormal in the pump. Hope that helps.

[Stefan]

Awesome, thanks for the response.

I suspect that the pump needs to be replaced. The sound is definitely coming from the back. But as I added fluid many times I suspect that it might have gotten contaminated.

[Stefan]

I got under the car and rechecked the lines and they looked fine. So I drained all of the fluid by disconnecting the lines and draining.

I disconnected the polyrib belt and turned the power steering pump by hand to get the remaining fluid out. The fluid did look a bit murky but I don't know if that's normal (I know it doesn't come out of the can that way). I refilled the system and got all of the air out using the factory recommended procedure.

The sound is just as loud as before. I used an electronic stethoscope to verify that the sound is coming from the pump and it was. So it looks like it's a new (actually rebuilt) pump for me.

Thanks again for the advice, folks.

[JP Rodkey]

Sounds like you did everything possible to pinpoint the problem and a new pump will bring joy. And thanks for posting your results.

[dynodon]

Just a thought, that any power steering pump, even perfect ones, will make noise if they are up against something on the body. This includes lines.

For example, I had a SHO Taurus that I installed a front strut tower brace on, and the brace touched a rubber power steering pump hose. The noise was so loud I didn't think it could possibly come through that hose, but when I moved the hose temporarily, and finally removed the brace, the noise went away.

So before you replace that pump, make SURE that all the hoses (and brackets etc) are away from anything that is attached to the body, or there are isolation clamps on them.

Don

[arctic silver]

Stephan,

I track my Cayman and have had 3 power steering failures. Ended up adding a cooler on the return line. Although it doesn't leak anymore, I think I messed up my PS pump sinbce I have very little PS at low speeds (OK at higher speeds), so i think that I too will soon replace my PS pump. Are you going to replace it yourself? Given that the Boxster and Cayman are nearly identical, we migjht share notes on how to do it the best way.

Charles (arcticsilver on this forum and the Cayman Club Forum)

*********************

I got under the car and rechecked the lines and they looked fine. So I drained all of the fluid by disconnecting the lines and draining.

I disconnected the polyrib belt and turned the power steering pump by hand to get the remaining fluid out. The fluid did look a bit murky but I don't know if that's normal (I know it doesn't come out of the can that way). I refilled the system and got all of the air out using the factory recommended procedure.

The sound is just as loud as before. I used an electronic stethoscope to verify that the sound is coming from the pump and it was. So it looks like it's a new (actually rebuilt) pump for me.

Thanks again for the advice, folks.

[Stefan]

I will definitely do it myself. I am planning to get a remanufactured pump and will probably replace it in a couple of weeks. I expect it will be pretty straightforward and I would be happy to take and share pictures.

[Stefan]

Just a thought, that any power steering pump, even perfect ones, will make noise if they are up against something on the body. This includes lines.

This is a good point. I did use an electronic stethescope to verify that the sound is coming from the pump. If I remember correctly, the pump is bolted directly (without any dampeners). I will definitely check to make sure it is mounted correctly.