Turning the steering wheel with the engine off overflows PS reservoir

[atikovi]

I was changing the right front wheel bearing on my 99 Taurus and during the job I had to turn the wheels right and left numerous times to remove and install parts and fasteners. After a while I see a pool of PS fluid on the ground and see the reservoir was overflowing. Why?

 

[mk378]

Many cars will do that. Turning the wheel pushes fluid out of the rack into the reservoir. When the pump is not running it does not return.

 

[tasch72]

I was changing the right front wheel bearing on my 99 Taurus and during the job I had to turn the wheels right and left numerous times to remove and install parts and fasteners. After a while I see a pool of PS fluid on the ground and see the reservoir was overflowing. Why?

My guess is when the pump isn't running, the high pressure side isn't getting pressurized and cycled, so your low pressure is backfilling the reservoir from the rack from the pressure of turning the rack

 

[atikovi]

OK next time I'll have to keep an eye on it.

 

[ka9mnx]

Yea, it will do that!

 

[JimPghPA]

I think that in order to do that the rack high pressure side would have to suck in air, but the seals of many high-pressure hydraulic systems are not designed to prevent air passing by them, especially when that air is going in the opposite direction of what the hydraulic fluid on the high side wants to go.

 

[Lubener]

I was changing the right front wheel bearing on my 99 Taurus and during the job I had to turn the wheels right and left numerous times to remove and install parts and fasteners. After a while I see a pool of PS fluid on the ground and see the reservoir was overflowing. Why?

That's normal.