Power Steering stiff when PSF hot

[MaximaGuy]

Yesterdat, with record temps in CA and while driving back home I realized my steering slowly getting stiff on my Highlander. Got home and check the temp of the steering reservior and it is really hot.

Hot fluids do loose steering pressure, curious if that has been experienced in other highlanders (may be I need a cooler if the steering fluid gets really hot).

I am concerned if the PS system has been under engineered for the Highlander.

 

[unDummy]

Many vehicles have underengineered components and fluids.

If your year allows the use of any Dexron ATF as the PSF, then flush it out with a quality synthetic ATF. RL, RP, M1, Ams,.... are some to choose from.

If you can't see a filter, feel free to add an inline filter. Magnefine, Wix, Transdapt, Permacool.... have inline filters that'll work. Filtering is lacking in most PS systems. The inline filters are an easy splice install. The pint/quart sized filters will need remote mounting, possibly hose extensions....but use cheaper filters and add fluid capacity.

An aftermarket oil cooler is also an option. Some PS systems run hot, especially during summer or when worked. A cooler will help.

 

[Big Jim]

Be careful about adding a filter. Make sure that it is specified for power steering use. Transmission or engine oil filters are not made for the pressures developed in power steering systems.

At the advice of a factory engineer, the steering and suspension tech that I worked with years ago added a filter to a troublesome power steering system only to have it blow apart sending filter media throughout the system. He had to disassemble the pump and steering gear to clean it all out as well as blow out all the lines.

I know tha power steering filters are available, but I'm not sure how easy they are to find.

 

[MaximaGuy]

I don't intend to put a filter in the path since regular drain and fills will keep the fluid clean but I would like to explore putting a cooler in the path if this is a problem on Toyotas.

One of my friend's 4Runner rack had to be replaced recently on his 2001 model, so I am really concerned about these racks. Toyota 4Runner's of late have had many racks replaced, well after warranty.

 

[Tempest]

Quote:

---

Transmission or engine oil filters are not made for the pressures developed in power steering systems.

---

Are PS return lines under the same high pressure?

For what it's worth, both of my V-6 vehicles have real tube and fin coolers as stock.

 

[Big Jim]

Return lines are not under nearly as much pressure as the pressure lines. That's why many of them are not built nearly as stout. The return hose is stronger than trans cooler hose though.

I really don't know the pressure in the typical return line, but I do remember that one incident clearly. It was a real mess.

 

[unDummy]

Most return lines openly dump into the PS reservoir. Where is the resistance to cause excessive pressure?
Return lines are also considered the low pressure side.

I guess a proper warning is that you should be sure to install the filter in the return line. There are probably some installed incorrectly on the feed to the pump or at the higher pressure output of the pump. This will eventually create messes. Also, undersized hoses can create issues. For mounting reasons, if you're running a distant remote filter, upsided the hose diameter.

Avoid using incorrect replacement hoses. I still see backyard clowns buyinging carb'd fuel hose and vacuum hoses, thinking its OK for 'other' applications. Mess would be an understatement.

PS pressure lines are tested at 1500PSI. PS return lines are tested to ~250PSI.
The actual working pressure is lower and the line burst is higher. Name brand ATF and oil cooler hoses, and oil filters, should not have any problems with return line pressure or flow.

 

[Tempest]

According to the Goodyear P/S Hose site, the return hose is low pressure, though no PSI is given

. The pressure side is 1500psi working, which is some serious pressure.

Their Transmission oil cooler hose is rated for 250psi working. I would think it should work.

ETA: I would think if a little plastic Magnafine could hold up to PS return, a larger industrial type filter would be OK?

 

[unDummy]

I've never seen 1500PSI on a pump. Even though the shop's pump testers were rated to 2000psi, you'd rarely see more then 1200PSI. PS pumps have internal flow and PSI valves. They don't exceed a given PSI or flow as demanded by the OEM system's spec. The PS pump tester will actually pinch of the PS pump completely(brick wall), to measure MAX possible pressure. The steering rack will never pinch off completely like that.
Even though the feed pressure is high, the resistance that causes the pressure is the rack.
The return line will not ever see that pressure. Its inner diameter and length is the only source of flow resistance. This is why return pressure is relatively low.
Also, most pumps rarely are big enough to pump more then a couple gallons of flow. They are flow regulated, and not just pressure regulated. Most PH8a sized filters should have no problem with 7-10 gpm of flow.
And, if your PS pumps flow valve broke, an oil filter would just hang out bypassing any capacity over its flow rating. If your PS pumps PSI valve broke, you'll blow out rack seals, the high pressure hose, its fittings.....

I'm just trying to reduce the fear of those considering a PS filter kit on their passenger cars or trucks. It is nothing to worry about if picking a name brand kit.