The cap for my power steering reservoir actually pops off and spills fluid everywhere.

I got a "deal" on a 2001 F250 7.3 with Zf-6, only cost me $2000, and it even drives(ish)! But it had been hit in the side and needed some work to get ship shape. Replaced a bunch of ignition components to fix a hard start issue. Had to replace the clutch master because the pushrod retaining clip was broken and the rod kept popping out. Now I think the clutch might be slipping, could be I just boogered the clutch bleeding, so that's next on the list. But for now, the REAL problem is the power steering.

See, I can't even really drive the thing because my brakes are spongey and I can barely turn the steering wheel when I'm moving. It has the hydroboost where it pumps ATF through your brake booster. I pulled the power steering pump apart and cleaned it up, got a seals kit from the store for $10 and replaced all the seals in it, then I bled the system. But I still don't have any power in my steering or brakes... but I don't think its because the pump isn't generating pressure. In fact, so much pressure is building up in the "reservoir" that its popping the cap for the reservoir off and burping fluid everywhere. I don't think its air because theres no bubbles, its all fluid. I could probably fix it by spending a few thousand dollars and just replacing EVERYTHING (pump, hydroboost, steering box, cooler, lines, etc.) but I'd rather diagnose it properly and only have to spend a few hundred dollars.

I suspect that somewhere there is a clog that is not allowing the fluid to circulate through the system normally, so the fluid is just returning via the hydroboost return with all the pressure that the PS pump can build. Could be clogged just about anywhere. But even if I start pulling hoses and components, I don't know how I'm going to be able do diagnose a bad hose or a bad hydroboost or a clogged steering box. Are there any diagnostics procedures that consider the whole power steering / hydroboost system so I can isolate the problem?

 

Is the pump even pumping out? it might be totally hooped. For example if you cycle the steering left to right to left over and over with the engine not running (pump not running) the steering gear will pump fluid back to the reservoir and overflow it (learned that the hard way). Lack of power steering implies not enough pressure probably from not pumping any fluid (basically recirculating within the pump because its worn out). On my '93 BMW 850Ci with hydroboost brakes, my brakes were super spongy and bad until I replaced the 30 year old accumulator. Might be part of your problem, might not be.

 

I'd assume tha generating enough pressure to pop the reservoir cap off requires the PS pump to operate. I don't know how it could pop the cap otherwise. There's certainly no charge left in my accumulator at the moment, but since I don't have steering either I don't think that's the critical element.

It looks like the pump is supposed to run at 1200 PSI, is that correct? I don't have a pressure gauge or anything to test that. I suppose I can just pop the return line off and see how far it squirts.

I was thinking about installing an inline filter because rockauto wants to upsell me one, it recommends one when you add hoses to your cart lol. I've seen people install them next to the cooler but it makes more sense to me to put it in the hydroboost return line. Any recommendations on inline filters? The ones rockauto recommends are "power steering" filters, I don't know if they are good for ATF.

 

Why would the pump pressurize the reservoir? The pump only goes one way. Fluid goes out the out and in the in on the pump. If fluid is overfilling the reservoir then it can't be from the complete opposite side of the pump.

 

Not sure what pressure it runs at but that number at least doesn't sound unusual. Taking the line off will tell you nothing whatsoever but you'll probably get to clean up a huge mess.
I wouldnt add a filter. Ford didn't do it and there are 10 billion trucks on the road doing just fine without it with tons of miles racked up. Mine has 285k no problems no filter.
I will say adding a suction filter (restriction) to a hydraulic system that wasn't designed to use one is a great way to cavitate and subsequently destroy your hydraulic pump.
I'm an electrical engineer in the off highway equipment industry but I did do a short stint in hydraulics engineering a few years ago. My stab in the dark without taking any measurements is your pump is worn out. When you steer it the fluid comes out of the steering gear and/or when you brake it comes out of the accumulator back to the reservoir and the pump is not able to keep up and keep the fluid circulating back into the system so it spills.

 

To diagnose you'd need a hydraulic gauge but the system only builds that high pressure under load. Plenty of those pumps laying around pull a part, worth a guess. Fords will push fluid back into the reservoir if no pressure and turning the wheels.

 

Well it was the pump. I got a reman from autozone that was 69.99 (+$25 core) but it was 20% off. Bonus: the clutch is fine

 

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