I previously had troubles with whiny, sometimes difficult, power steering when it was warmed up. I assumed this was because the PO topped it off with coolant so I of course flushed it with new ATF which disappointingly only made a small difference.

Finally I rebuilt the system with all new lines and new pump from an S10 pickup. It's basically the same pump, but with higher output. Everything seemed fine at first. I started it up and drove around the block, turned the wheel lock to lock, and it seemed nearly silent.

We went for a trip this weekend and found out it wasn't fixed after all. It had never got fully warmed up driving it around town at relatively low RPMs. Now we had been freeways, long roads, hills and the PS pump became more and more noisy. Eventually it whined so bad I could hear it while just driving straight. I pulled over and found it had spewed PS fluid (S10 pump uses PS fluid) everywhere out the release valve hole on the cap. I tried to refill it but it just kept spewing out more.

To keep this short, here's what I found after some diagnosis:

The warmer the engine is, the louder it is. When it's cool, it's quiet, nearly regardless of RPM.

The higher the RPMs, the louder it is. At low RPMs, it's quiet (even if hot and whining at higher RPM) and turns locked to lock, even stopped, just fine. When it's hot and at higher RPMs (like when driving) it gets louder and louder until it's scary and spit out PS fluid.

The RAVE says most over pressure situations are caused by a faulty relief valve in the pump. That's possible, but since it had a similar (but not as bad) whining problem with the old pump too, that leaves the PS box.

Is it possible for something in the PS box to cause these symptoms?

 

The steering box takes the incoming flow and applies it to the "rotary valve" which sends it to push the steering left or right. Excess fluid is returned with the return line to the tank. Would think this would show up as tank getting empty at speed if the rotary valve blocking this. At mid point, it should put equal pressure to both directions, and return balance to the tank. All sorts of seals, orifices, and such for you to work on in your spare time.

 

I know of a number of people running the higher pressure pumps with no problem. Is it possible your box is bad, Yes, sure could be, just not sure how to tell you to test it before replacing it.

 

In my wildest imagination I would suspect the gear box has a partial blockage or internal seal rupture or something along those lines causing the fluid to overheat. By internal seal I mean you'd not notice more external leakage but how the fluid is routed internally. Your not configured any different than any Disco and yet two identical issues. The gear box is the common denominator between both ps pumps and what makes it unique is the PO ran coolant through it. Oil and water do not mix. If I where to run a motor with coolant added to the engine oil it would lead to engine failure. The gearbox won't fail (can be used without hydraulic assist) unless it a incurs a catastrophic mechanical failure. The gearbox can be rebuilt with a kit. It may not even need that but just a good tear-down and cleaning. Might just be a glob of crud preventing flow through, it's now been exposed to three different types of fluid........who knows. I don't remember if your running a heavier bumper than stock but I personally noticed a difference in the front feel with just a brush guard installed and it adds a heavier feel to the steering. It's slight but I know my truck with and without and there is a difference. So that coupled with a compromised gearbox and you boil the fluid. It's worth taking a look at the box. I'm going way outside the box with this because I just don't know why it would overheat. The only other thing I can think of is hose routing or transfer of heat from the head through the mounting. Mike may have a point that it's bad? Was it a rebuilt unit, new or junk picked?

 

Pump is the same A1 Cardone rebuilt one that everyone seems to be buying. PS lines are run with stock routing as far as I can tell in photos. The ends only connect one way too.

Any suggestions for replacement box? Rebuilt, new aftermarket, OEM?

 

Sounds like something is blocking too....

I rebuilt the box myself and can see if one of the internal soft part blows, it can get into one of the ports and block.

Get a warranty rebuild unit....I am.

 

I'm looking at getting either the $549 new box from AB with arm, or a $272 rebuilt box without arm. $272 is nicer, but then I have to mess around with pulling and pressing the drop arm, and I'm not sure of the reliability of box rebuilds.

 

I'd see if Will Tillery has anything in the way of a steering box.

 

Pressing the arm out was a BIATCH!!! When I rebuilt mine, I had to literally cut off the arm. It was stuck on there. I did had to get another one, but they are only about $20 for a good used one anyway....

 

Will Tillery or Paul Grant.......(I just happen to be wearing my Rover^Guy T shirt today, Paul you need to make stickers.......)

The rebuilds leak in about a year. Never heard a good story on em and that's allot of reading in four years. I was interested in the Classics for awhile (still am), they have the same box.