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Steering fluid foaming

Why is power steering foaming in reservor. I tried to bleed the air from it by turning the steering wheel lock to lock for about 45 minutes but air bubbles keep comeing out. No fluid leaks on garage floor. 1990 lincoln continental.

Probably because the power steering fluid is old. One of additives that’s included in power steering fluid is an anti-foaming agent.


I completely flushed fluid until it ran clear. The brand is MAG-1 power steering fluid.

Were you turning it back and forth with the engine running? The pump moves it through really fast. With the engine running you’ll just keep pumping foam through it. Try leaving the wheels straight and running the car for just a few seconds. Check for foam and if there is any let it completely clear. Then start it again for a few seconds…Do that several times. Then jack up the front & get it on stands. Leave the engine off while slowly turning back and forth, stop to stop, a whole bunch of times. See what that does.

If none of that does it, then it is possible that you have a leak. A small enough leak might pass little to no fluid, but could still suck in air.

The pressure relief valve may be stuck, causing the pressure to increase to the point of cavitation. The relief valve is accessed through the front of the pump. Remove the large bolt and the pressure spring will be easily pulled out and a magnet should easily pull the pressure plunger out. If the pressure plunger is seized it is most likely causing the foaming.

This happened on my '89 Accord. Problem was a shaft seal leak on the power steering pump was actually causing air to get sucked in through the pump and pumped through the system. Replaced shaft seal and problem solved.

Yes, I would bet it’s a small leak on the suction side of the pump. It’s not an unheard of problem with Lincolns.

In the bottom of the fluid reservoir there is a filter screen that can get plugged up with hose particles, starving the pump and causing it to suck air…Remove the reservoir and clean the screen…Most Fords are happy with Mercon ATF in their P.S. systems…

I had the engine off and it was up on jack stands. I turned the wheel back and forth for about half an hour last Friday then Saturday morning I did it again for about 45 minutes. I started the car for about 3 seconds on Sunday and it was still foaming. Thanks for this and all the other replies. I will see about trying them out. One more thing. The problem started after I did an engine swap and used the PS Pump that came on the new/used junkyard engine. Maybe this pump is bad?

How do you remove the reservoir? Thanks.

Given that this is the case I’d next suspect the kind of leak mentioned below by nfs480 & tardis.

I don’t know anything about the pressure relief valve though, as mentioned by Rod Knox and it sounds pretty straightforward to have a look.

Thanks for all your suggestions and sorry for the long delay in responding. I finally got it taken care of. I had to have someone help me thoroughly bleed the ps system. Thanks again

Hi Joseph, it’s 10 years later and I have the same problem. How did you end up bleeding the power steering?

Click on joseph’s avatar . . . then you’ll have an opportunity to send him a private message

Otherwise, he probably won’t be aware that you’re trying to contact him