vacuum test of steering system

What kind of leak rate should be expected when vacuum testing the steering system, ie hooked up vacuum pump with gage to the reservoir cap? I am getting leakage, but don't know what is to be expected? When I bench test it is tighter than when installed, the hoses and gear box show near zero leakage, the reservoir and pump tested on bench is fairly leak tight, but when installed, the leak rate increases, and it seems to be worse as belt is tightened. This to me indicates a shaft seal issue, along with a worn bearing, but this is a new high end pump. This is my first experience with this kind of power steering. I had gotten this new pump but made the mistake of reusing the o ring between reservoir and pump, and although I was able to bleed the system well, I had a drip from the used oring. Installed brand new oring, and drip stopped, but now I can't bleed the air all out due to leakage, someplace. But the dripping stopped. This really have me confused, with dripping leak I was able to purge air out, fix leak and can't purge all the air out.
I made a clear cap for the reservoir so I could see inside while under vacuum, I can see air bubbles entering now, apparently from the port to the pump.

This is driving me nuts.

Advice please? Supposed to go wheeling at Hollister tomorrow on my first outing with this jeep, but that won't happen at this rate. I have spent the last several months rebuilding the front axle, new gears, axle shafts, arb, new bushings, ball joints, tierods, etc... Now I have this power steering issue.

So what leak rate is expected?

Thank you!

Why would you try to pull a vacuum on a pressure system? Shaft seals only seal in "one direction". I bought a high $ PSC pump that leaked out of the box and had to replace it!

This is a link to using a vacuum to purge the air...
https://www.explorerforum.com/forum...our-power-steering-pump-steering-rack.360751/

But I used the above method without running the engine, as I dont want to run my new steering pump until after the air is removed.

I tried the lock to lock method with engine off, 50 times, x4 attempts, and it still has air. After that I tried the vacuum pump, it is effective at outgassing the foamy fluid after I run a very brief, seconds long engine run, that is when I noticed the system wont hold vacuum, worse when the belt is tightened.

This is a new AGR pump. Supposed to be factory tested. I had followed the AGR bleed instruction to the letter. The pump has been in and out a half dozen times, wasting days on this so far.

Very frustrated by this, I am really beginning to hate my XJ, all the work I have done, rebuilt the axle, new bushings, tierod ends, ball joints, ARB locker, manual hubs, and still cant drive it. Maddening!

Any more advice?

JEEP, "just empty every pocket". If your going to own one you gotta pay!

I would not condemn anything for that reason. You may just need to go drive it. Get the fluid warmed up and see what happens.

I hesitate to run it, as even when run for several seconds after purging, after a few seconds the pump gets noisey, and the fluid foams up big time.

RCP Phx said:

Why would you try to pull a vacuum on a pressure system?

Click to expand...

A former member, JJacobs, recommended putting a light vacuum on the reservoir to pull air out of suspension in the PS fluid.

When I replaced hoses and pump on my '90, I kept about 10" vacuum on the reservoir while I cycled the steering: No foam! I did notice the pump would whine under vacuum. Just for S&G I put more vacuum on the reservoir, the pump whined louder, but no foam. Release the vacuum, no sound from the pump.

Vacuum bleeding of a power steering system is new to me but it is the same method that has been used forever to bleed or remove air and moisture from A/C systems, before recharging.
I have had steering racks that take forever to bleed, using the conventional method. It would be of great help to speed the process up.

http://www.cardone.com/tech-help/steering/how-it-works-best-practices/vacuum-bleeding

http://my.cardone.com/techdocs/PT 20-0002.pdf