Power Steering pump differences

[georryan]

Ok, so I'm picking up a newer steering rack, and I am getting a power steering pump with the deal.

I know that my power steering pump needs to be rebuilt, and I'm considering just doing that, but I was also curious what the differences in the pumps were through the years. I know that the threading specifics changed a little, and eventually they moved the reservoir off the top of the pump.

Does any one know what if there were pressure differences through the years and models? Also, the GC's and up pumps had an electrical connector if I am correct, where ours did not. Does that connection affect the functionality of the pump at all, and if so what would be the drawbacks from using a pump that had one but not plugging it in?

If anyone wants to chime in with a thesis on how these pumps work, that is fine by me as well as I don't fully understand how they work, or what can be done to modify or alter their stock performance for more or less pressure, or whatever else. I hear about shims being adapted and such.

I'm doing research as well, but anything that could be added to my knowledge from the board would be appreciated.

[kimokalihi]

I would also like to know all about subarus different pumps and how hard/expensive it is to rebuild one. My power steering sucks but I don't know if its the pump or the lines because they go a little kinked and I straightened them out but they're a bit flattened still. Anymore messing with them and they'll surely break so I need to replace them with aftermarket braided hydraulic hose eventually. If I try to make really quick turns like you would in autox the steering nearly locks up. It gets super hard to turn for a second. Not good. Daily driving you never notice it but it doesn't like sharp fast turns.

I have a wrx pump with hoses and remote resetvoir too I might use one day but I'd have to get custom lines because the threads won't fit my lines.

[Legacy777]

Have you seen my thread here?

http://bbs.legacycentral.org/viewtopic.php?f=11&t=24143

There is valving that controls output pressure. It's controlled via a spring. In theory you could reduce the spring force to reduce the amount of output pressure to the steering rack and increase resistance.

I'm not very familiar with the electrical connector pumps, but those could serve two purposes, one is to provide the ECU info when pump is under load so it can adjust the idle speed, or two it could be used to adjust pressure when the car is above a certain speed to improve steering feel, but still provide good assist when parking, etc.

Regarding your auto-x issue, I would suggest checking your PS belt and belt tension.

[kimokalihi]

Ill check the belt but I think its the lines restricting flow or the pump that's 190,000 miles old. I have yet to do autocross I'm just saying if I were the steering would just about lock up on me.

[georryan]

Kimo - I read a post on nasioc where a guy was saying that he had a newer rack, but was using his stock GC pump. He was having some of the problems you are mentioned I believe. He said that he was also running an UOR underdrive crank pully. He felt that the under driven pully affected his pumps ability to work effectively with the rack.

With the underdrive pully I would get a kind of kickback from the steering at near full lock. IE the pump wasn't flowing enough for the increased ratio of the STI rack. I switched the underdrive pully for a stock crank pulley and the problem was solved.

I don't know if that applies to you fully or not, but there you have it.

Josh - thanks for the reminder of you post. I think I've read it before a while ago. I'll read up on it again. You haven't had any experience with or know anyone that has run a newer power steering pump on our cars without using the electrical connection?

[entirelyturbo]

If you're going to attempt the pump rebuild yourself, read through the thread Josh posted thoroughly, even multiple times if you have to.

Though they may not seem complicated, they're easy to screw up... I had to redo mine twice before I got it right

I recall the pumps changing either for 92 or 93; the shaft bearing and seal got larger and the body did as well to accommodate them. So if you're going to replace the bearing (they come as a shaft/bearing assembly from Subaru) it might be a good idea to find out exactly what car it came off of.

I've never seen a US 1st-gen Legacy pump that was able to vary fluid pressure electrically. If you have a pump with a switch on it, like Josh said, it's probably to signal the ECU that the fluid pressure is rising so it can adjust the idle accordingly. But if your car isn't so equipped, then you can just leave the switch there unplugged and it won't hurt anything.

[Legacy777]

Josh - thanks for the reminder of you post. I think I've read it before a while ago. I'll read up on it again. You haven't had any experience with or know anyone that has run a newer power steering pump on our cars without using the electrical connection?

No I haven't had any experience with any of the newer pumps without the electrical connector hooked up. I can try looking through some of the newer factory service manuals to see if I can determine exactly what the electrical switch does.

[Legacy777]

I recall the pumps changing either for 92 or 93; the shaft bearing and seal got larger and the body did as well to accommodate them. So if you're going to replace the bearing (they come as a shaft/bearing assembly from Subaru) it might be a good idea to find out exactly what car it came off of.

Based on my experience and the factory parts book, there is no difference in the shaft bearing or seal on the first gen Legaciy PS pumps. They're all the same. There are some wafer type springs only on the 90-92 MY's, but everything else is the same.