Carpokes Porsche Forum

Any PS Pump experts or semi-knowledgeable folks?

I recently replaced the seals in my PS pump but I haven't reinstalled it on the car yet. I had previously replaced the seals approx five years ago in 2018, so I've had the pump apart before (which makes me question proper alignment).

Will anyone confirm for me the correct alignment of the internal ports (circled in green here).

When those internal ports line up (as in face each other when assembled), the external features (in red paint pen) line up sensibly. The rotation arrow lands on the side with the output port, and the wide ridge casting features align with each other on the side with the input port.

I can't say for sure that this is the factory alignment of the pump halves, since I've had the pump apart before. Though unlikely, 'cuz I'm usually pretty good about such things, it is conceivable I put the halves together "out of phase" when I had it apart previously.


The reason I replaced the seals a second time just recently is illustrated by this pic. It shows the hourglass-shaped (butterfly) seal sucked (or pushed?) into the little ports.

However, wouldn't the area inside the butterfly seal, and thus the ports, be on the high-pressure side of the pump? What could cause the seal to be sucked/pushed in?

I encountered this "sucked in" problem almost immediately after resealing the pump in 2018. I barely drove the car between then and recently when I encountered the "sucked in" problem again (and wrote about in This Post).

I found three additional examples of posters on RL describing this problem after a PS pump reseal, but there was no "here's how I fixed it" to accompany those posts.

Prior to my recent pump reseal with a new seal kit, I had removed the pump, re-seated the butterfly seal, and put the pump back onto the car. However, that's when I thought, "dammit, just order a new seal kit already and stop messing with re-seating that seal once a week".

So I didn't refill the system. I did reconnect the hoses (so they weren't floppin' around under the car drippin' stray fluid everywhere). I drove the car with the PS belt removed while I waited for the new seal kit.

When i removed the pump to reseal it with the new seal kit, after not having been powered in the interim, the old butterfly seal (the one I had realigned) was again sucked/pushed into the same little ports as before. This occurred after maybe 40 miles of driving the car with unpowered steering (belt removed).

What does that scenario indicate?

All insights are welcome, including ones that reveal dumb things I might have done.

After watching a number of YouTube videos about power steering pumps in general, every one of them talked about a "pressure relief valve" or "flow control valve". I thought, "Huh, I don't remember ever fussing with that before."

Since my PS pump was still conveniently on my workbench (with its fresh new seals), I took it apart and found the valve and cleaned it.

Behind the center four-pronged "clip" in the dead center of the back half on the pump was the valve I sought. That clip is easily removed with a little pick. The assembly is spring loaded, so devise a way to catch the parts that want to launch themseves.
That bit has more parts inside, and there is no obvious way to hold the round base to remove the 12mm cap. I used a rag along the pressure release groove (with the two holes) and a small vise grip set as loose as I could get away with. DON'T gouge up the larger outer diameter - it must have a tight sliding fit in the bore where it resides.

Inside that are even more parts. This has a even higher "boing factor" and even smaller bits that yearn to fly. The cap is a tight press fit, though it is possible to twist it free by counter-holding the squared off end of the tube with a small wrench. The spring pressure will absolutely launch the two tiny bits inside.
I cleaned all this stuff in my ultrasonic parts washer, as well as the entire back half of the pump itself. There are passages machined into it, like the one the flow control valve interacts with within the central bore.

I blasted everything clear with compressed air and reassembled everything. It remains to be seen if this accomplished anything at all. I believe the flow control valve operates at a higher pressure than I can deliver with compressed air, so I can't easily test it.

However, there was a tiny amount of gunk within the inner-most assembly. It's not hard to imagine that tiny orifice in the 12mm cap being clogged or gummed up.

This video series on YT was useful and interesting. It's not specifically Porsche/German/ZF, but it is comprehensive and well done.

More good stuff usury! Amazing. I cannot fathom the patience to deal with disassembling that flow control valve or whatever it's called. There are a lot of tiny spring-loaded parts stuffed into that small whatchamacallit. I bet putting it back together was interesting. I'd like to meet the engineer who visualized and designed that. What a mind!

Hope it solves your dilemma.

I thought I had a post up on RL about my steering pump rebuild, where I looked to document how exactly the halves line up. From memory, since it looks like I didn't actually post anything, those holes you point out should line up.

Cheers

Zirconocene wrote: Tue Aug 15, 2023 10:32 am those holes you point out should line up.

Cheers

Excellent! That makes the most sense to me, too.