So I had to replace a power steering hose...and all went well. I fill it up with fluid and all is still well.

but when the car cooled down, fluid came overflowing from the tank, reservoir, whatever its called. It was coming from under the cap.

Should the cap be holding this pressure? Is the fix as easy as buying a new cap?

you put too much fluid in?

No, I put the right amount in. It runs fine until it cools down and overflows. When I go to drive it again, the steering is jumpy like there isn't enough fluid in it.

Why would something overflow when it cools down?

Things expand when they cool (think of the ice trays in your freezer)

See, I don't know a lot about these things.

I thought that maybe when the pump isn't running that maybe the fluid has the tendency to run back into the reservoir. Thats why I'm asking if the cap need to be able to hold pressure.

All I know is that it runs fine when I fill it up, but when I turn it off it starts overflowing in a couple of minutes. This results in low fluid and jumpy steering....and a loud, obnoxious sounding pump.

Things expand when they cool (think of the ice trays in your freezer)



Uhhh.

Things expand when they cool (think of the ice trays in your freezer)

Power steering fluid expands when it gets hot. It expands a LOT, which is why there is different fill lines for hot and cold.. I guess it could expand when it FREEZES..but the freeze point for power steering fluid is somewhere around -42f.

The reservoir tank should never fill up, so unless your cap is somehow mounted on the side or upside down, you probably have too much fluid.

Something else must be wrong, then.

I assure you that I'm putting the correct amount of fluid in. I know how to fill something to the line.

I fill it up while at idle, and it quiets the pump and the ps is fine. Then when I turn off the motor, all of the fluid i just put in come pouring out of the reservoir. this results in the fluid being about 3/8 qt. low and my ps getting shaky.

Any other reason it would be doing this? (I'm 100% positive its not because there is too much fluid)

Things expand when they cool (think of the ice trays in your freezer)...

Doesn't water act the exact opposite of most shit because it gets loaded with air when it freezes?

Hot=faster moving molecules=larger spaces between molecules=larger volume. It's been a while since highschool chemistry, but mercury expanding in a thermometer supports this.


EDIT: http://www.word-detective.com/howcome/waterexpand.html /EDIT

Also, I don't think there should be pressure in the reservoir, I've driven cars with leeks that had to be topped up everyday, and I don't recall much if any pressure while removing the cap.

Thanks for the info.

I got it figured out, i guess.

I cranked it up, topped it off and then drove it turning the wheels like a maniac for about two miles. I went back home and turned it off and only a little spilled out from where I over filled it about an ounce or so. So...I don't know if there was still a shit ton of air still left in it (even though I took it on an 8 hour drive over the weekend) or something mysterious happened.

Meh, its fixed now. Thanks for helping.

Thanks for the info.

I got it figured out, i guess.

I cranked it up, topped it off and then drove it turning the wheels like a maniac for about two miles. I went back home and turned it off and only a little spilled out from where I over filled it about an ounce or so. So...I don't know if there was still a shit ton of air still left in it (even though I took it on an 8 hour drive over the weekend) or something mysterious happened.

Meh, its fixed now. Thanks for helping.

When you initially put a hose on, you had air in the line. Whenever you replace a hose you need to bleed the system of the air, kinda like the brakes. What you should have done is while the car is not running, jack the front end up and turn the wheels lock to lock and hold it at the end of travel and watch the bubbles come up from the line. repeat on the other side. When you started the car with the air inside, it was like you were making a milkshake and made a million little bubbles, and when all the dust settled, it pushed the fluid out the cap because it is not a pressurized system. Since you have not done this procedure, then you may still have little bits of reminder of the bubbles until they are all worked out of the line. Sorry I didnt read this thread when it could have been most helpful, but there you go anyway.

Something else must be wrong, then.

I assure you that I'm putting the correct amount of fluid in. I know how to fill something to the line.

I fill it up while at idle, and it quiets the pump and the ps is fine. Then when I turn off the motor, all of the fluid i just put in come pouring out of the reservoir. this results in the fluid being about 3/8 qt. low and my ps getting shaky.

Any other reason it would be doing this? (I'm 100% positive its not because there is too much fluid)

You overfilled the power steering fluid. You are supposed to fill it with the engine off. While the pump is running, it will suck down a lot of the fluid from the reservoir, giving it an appearence of being low. If you fill it with the engine running, all of the extra fluid that has been sucked into the system will return to the reservoir, and overflow when you shut the engine off.