Power Steering fluid foaming - can't find any leak.

98xj. 6.5" lift, 35" shoes.
PS has always felt a bit weak in this rig, but not weak enough to bother spending any time on it. Well, now it's super weak and starts screaming at me whenever I wheel.
Last time I was out wheeling, the PS pump started wining real bad at high RPM and I couldn't turn left at all. Would turn right just fine. Let it cool down and sit for a bit and noticed the PS fluid was pretty aerated. Once the bubbles worked their way out, PS worked stronger again, but it's doing this every time I drive now.
Everything is clean, can't find any leaks. It must be sucking air in, but where would there be vacuum on the PS pump?

The only thing I've changed recently was tightening the belt. Is it possible that it's a bit over tight and putting too much strain on the pulley, and causing the leak at the pulley seal?

Have a spare from a 95. Doesn't fit 98 head mounting .

If it's just while wheeling or otherwise overworking the stock power steering pump, you are probably just boiling the fluid. 35" tires in the rocks means it's time for a cooler at least.

donthelegend said:

If it's just while wheeling or otherwise overworking the stock power steering pump, you are probably just boiling the fluid. 35" tires in the rocks means it's time for a cooler at least.

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I supposed it's possible the fluid may have been overheated at some point, but the steering has gotten harder in general over the past few weeks. Right when I start it up cold, I pretty much need to rev it above 1000 to turn it easily. My steering WAS very light before, even with the 35's and new steering.

That said, if it turns out the steering box and/or the pump need replacement, what's a good upgrade? I've heard the dodge boxes will bolt up, but should I also be looking for a bigger pump?

Check the P/S pump reservoir cap. After a drive, shut down the engine and slowly
remove the cap. If you hear a distinct "whoosh" and see a bit fluid vapor (it's sort of
like popping open a can of soda pop) - then the cap is bad.

Don't bother trying to fix the cap. Swap the reservoir cap for a new one.

What happens: After shut down, the pump, fluid, and (normal) air in the reservoir cools
and contracts, and creates a vacuum. If the vent on the reservoir cap is bad, then air is
gets sucked in through the pump seals and the fluid becomes aerated.

What brand fluid you running? Have a cooler? Has same issue with bad steering box and cheap fluid

get a cooler in there and some royal purple. If it still boils over swap out the pump. I bet a cooler and some good fluid will probably do it.

If it's overheating, wouldn't it just make sense to go to a bigger steering box, rather than adding a cooler?

Also, I'm not sure that it's heat related. When I start up the truck cold, it starts foaming pretty quick. Doesn't seem to matter if I let it heat up first or not.

blistovmhz said:

If it's overheating, wouldn't it just make sense to go to a bigger steering box, rather than adding a cooler?

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I don't think it makes sense to not run a cooler on a rock rig, but yes going to a bigger box also makes sense. Plenty of people make both small and large bore boxes work though, you just have to evaluate the whole system.

Also, I'm not sure that it's heat related. When I start up the truck cold, it starts foaming pretty quick. Doesn't seem to matter if I let it heat up first or not.

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Yeah that sounds like something else is wrong. My gut says to suspect the pump first, but hopefully someone with more experience can confirm/deny that.

A V8 WJ pump is an upgrade to the XJ pump if you want to go with a junkyard upgrade. Minor modifications to swap it into an XJ.

No it would make more sense to do a cooler . The only bigger bore options are a Durango box and a 80s true j20 box. J20 is 4 bolt and impossible to find. They usually give you a j10 box. Even with a bigger bore box you will still over heating issues if you don't add a cooler. A bigger bore box won't magically dissipate heat better to the point where you are no longer over heating .i still had to run a cooler withy j20 4 bolt big bore box.
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If you have assist steering one direction but not the other, that's a bad box. The pump might have been killed by some metal debris from the box going out, but uneven power assist is box.