Question about Power Steering System and how it works

[Montego Murph]

This weekend I changed my power steering fluid using the "return line to jug / turn the steering wheel back and forth" method. This works really well for me when I have an assistant, but was sort of annoying solo because I couldn't keep an eye on the fluid level as I turned the wheel, and I ended up getting air in the system.

I was pondering how the system works, and why using this method changes the fluid (moving the steering wheel turns the power steering rack into a piston pump) and was wondering if one could accomplish the same results using a MityVac attached to the return line and sucking fluid through the system?

Granted this could reveal all sorts of new annoyances, but it would decrease the risk of draining the reservoir and requiring a bleed.

Thoughts?

 

[aemravan]

I am in the process of putting together a wrecked '03 4runner that had front-end damage, long story short it pretty much dumped 80% of the PS fluid during disassembly.

I'm not saying this is the correct way, but over the years, the way that I have dealt with the PS pump/fill/air bleed is to just top off the reservoir, leave the cap off and cycle the steering from lock-to-lock each way a few time and then turn it on and do the same and leave it running for a few minutes. I just filled the 4runner reservoir last night doing the same thing and for the first 3 minutes or so definitely had some air in the system that burped its way out eventually and fluid dropped to the necessary level. I could actually see the air working itself into the tank and bubbling out.

 

[firebirdguy]

just dont turn the wheel so many times to empty the reservoir. when i did mine solo i found about 2 times lock to lock was enough to drain it without getting any air in it. & you can overfill the reservoir during the flushes to ensure it doesnt go dry.

 

[Montego Murph]

just dont turn the wheel so many times to empty the reservoir. when i did mine solo i found about 2 times lock to lock was enough to drain it without getting any air in it. & you can overfill the reservoir during the flushes to ensure it doesnt go dry.

For some reason this caught my attention. What configuration is your 4Runner? I have an 03 V8 4x4, and one pass from lock-to-lock pumped out the reservoir contents (filled to about where the reservoir starts to curve. Maybe different models or years are different?

 

[royal T4R]

04 V8 chiming in

Just redid my entire front suspension including steering. With the wheel pointed straight ahead turning full lock to one side then full lock to the other side will drain my entire reservoir as well.

 

[firebirdguy]

For some reason this caught my attention. What configuration is your 4Runner? I have an 03 V8 4x4, and one pass from lock-to-lock pumped out the reservoir contents (filled to about where the reservoir starts to curve. Maybe different models or years are different?

08 v6. front wheels lifted off the ground & reservoir overfilled almost to the top. was able to get about 2 times left to right but not hitting the stop all the way, just right up until resistance was felt, 3 or 4 of those cycles & the fluid was clean & red.

 

[CarlosV]

08 v6. front wheels lifted off the ground & reservoir overfilled almost to the top. was able to get about 2 times left to right but not hitting the stop all the way, just right up until resistance was felt, 3 or 4 of those cycles & the fluid was clean & red.

2003 V6. Basically the same 2 weeks ago. Still some foam came into the reservoir when turned engine on, that settled, refilled and no problems.
Valv. Max Life. Learned here. Thanks guys.