ACURA TSX PS Pump

[artbuc]

Getting ready to replace the PS fluid in my niece's 2007 TSX. Surprised to see the PS pump is above the reservoir. Did some Googling and discovered Service Manual actually tells you to run the pump dry to remove old fluid. I can do that, but my question has to do with normal operation. What keeps the fluid in the pump suction line from draining back into the reservoir every time the car is turned off? Seems like this design would cause a dry pump start-up every time the car is turned on, not to mention getting a slug of air into the system. Seems very weird to me to have an elevated PS pump without a flooded suction line. Thanks.

PS Can't I remove old fluid without turning car on by just turning wheels lock to lock and collecting old fluid from the return line? I really don't like the idea of running the pump dry.

 

[Hokiefyd]

Good observation. I've never really thought about it, but there must be a check valve somewhere. I just siphon all the fluid out of the reservoir, replace, and do that a few times with a day of driving in between. True, the new fluid mixes with the old pretty quickly, so you never get a true fluid exchange, but I do this simple drain/refill every 15k miles, when I also do the AT fluid drain/refill. It's easy to remember and keeps fresh fluid in the system.

 

[JHZR2]

I do the same thing - siphon and then replace. Do this a few times, either in one shot more or less (with some driving or at least turning of the wheels to get it to circulate) or once per OCI type of a thing seems to work well.

To me, pulling hoses and running pumps dry are good ways to make a mess.

And at least on my MB, run the pump too low trying to do a flush, and it will make a frothy mess. So Id be wary of running the pump dry.

 

[Tegger]

Originally Posted By: artbuc
PS Can't I remove old fluid without turning car on by just turning wheels lock to lock and collecting old fluid from the return line? I really don't like the idea of running the pump dry.

Just follow the factory shop manual exactly. Running the pump dry during the change will NOT cause damage.

If you cannot raise the front end off the ground entirely, raise each wheel in turn and place a section of newspaper under them. This will reduce friction enough to make the wheel easy to turn during the drain procedure.

Ans use GENUINE HONDA power steering fluid ONLY. This comes from your local Honda/Acura dealer. Any other fluid will cause leaks.

 

[artbuc]

Thanks for the replies. Yes, I have the Honda fluid - read too many posts of folks having problems with aftermarket fluids. After thinking about this some more, the pump suction line can not drain because there isn't any way to break a vacuum (pulling a straw out of water with your finger on the end). The pump is positive displacement and self-priming.That is why, I think, the Service Manual says to start the car. The pump acts as a compressor to blow out the old fluid. For the brief moments without fluid, the pump wear surfaces are still wet with old fluid so they are getting enough lube to be ok. This is all starting to make sense.

 

[Tegger]

Originally Posted By: artbuc
Thanks for the replies. Yes, I have the Honda fluid - read too many posts of folks having problems with aftermarket fluids. After thinking about this some more, the pump suction line can not drain because there isn't any way to break a vacuum (pulling a straw out of water with your finger on the end). The pump is positive displacement and self-priming.That is why, I think, the Service Manual says to start the car. The pump acts as a compressor to blow out the old fluid. For the brief moments without fluid, the pump wear surfaces are still wet with old fluid so they are getting enough lube to be ok. This is all starting to make sense.

You are correct on all counts.

The important thing is to follow the factory manual's procedure to the letter.

If the fluid should get frothy (which it may not), don't worry about it. Just top up as needed until the level is correct again.

 

[Vikas]

I believe both Preston and Coastal make compatible power steering fluid for Honda/Acura. I do not recall anybody complaining problems with their usage. Both used to be available at local Walmart.

 

[artbuc]

Job done. Took two 12 oz bottles. Still need another flush to get things as clean as I would like. Thanks for your help.

 

[JHZR2]

so did you run the pump dry?

 

[artbuc]

Yep, followed Service Manual plus a little more. I removed the reservoir to give it a good cleaning as there was a fair amount of debris on the screen. The pump was quiet during evacuation. It whined a little as I added fluid and the fluid did get frothy until I added about half of the second bottle. I did it myself so I didn't see the old fluid as it was pumped out. I just did 3 lock-to-locks at idle per the Service Manual. Oh, I had the front end on jack stands as I had just finished installing new rotors & pads.

 

[yonyon]

Originally Posted By: artbuc
I can do that, but my question has to do with normal operation. What keeps the fluid in the pump suction line from draining back into the reservoir every time the car is turned off? Seems like this design would cause a dry pump start-up every time the car is turned on, not to mention getting a slug of air into the system.


You answered your own question there, dincha? Look, for the fluid to drain back to the reservoir air would have to replace it, unless the pump were so much higher than the reservoir (the pump would never work in that case) that the weight of it overcomes the force of ambient air pressure. It's that air pressure keeping the fluid from draining the pump and generating a small negative pressure in the pump. The pump sucks/siphons the fluid up out of the reservoir.

Just for fun, try using a vacuum pump and a couple few feet of clear tubing to see how high you can suck your used PS fluid from a pail or bottle. That's how much higher than the reservoir the pump would have to be to acheive drainback sans a leak.

That said, the the fluid level in the reservoir were so low that it's below the outlet to the hose the the pump, this allows air into the hose and the fluid can drain back from the pump, but only until the fluid level in the reservoir goes up to the top of the outlet.