Power steering pump leaking out cap

Hello
So I replaced my power steering pump because it was leaking from the shaft. I replaced it with a new assembly that came with the pump, reservoir, and pully. I did the bleed as per the manual and used atf+4 fluid. I had to bleed the system in other occasions because of changing parts and never had any problems with it. So I’m getting a weird leak. It seems to be coming out of the cap but not all the time. I drive it to work about 10 miles away and it doesn’t leak, but when I go on a long trip there is fluid coming out and running all over the reservoir. I stopped and checked the fluid right away after stopping and it is not over full or foaming. I don’t hear any whining pump noise so it’s weird to me. Could it be just a bad cap. I believe the pump is an aae pump. This is an 03 3500 diesel nv5600. Obviously you can’t get an over full without air doing it and I don’t believe the fluid would steam out but I’m kinda at a loss unless a seal is not sealing well and leaking air in at high rpm’s.

 

Maybe the accumulator on the hydraboost is not holding it's charge and sometimes leaks back and overfills the pump. Did the new pump come with a fill cap/dipstick or did you use the old one? Try running it slightly low and see what happens.

 

The high pressure lines have small orifices that can become clogged over time, trying back flushing them with compressed air from either end if lowering the fluid level doesn't help.

This was one of the first things I fixed on my 03, previous owners left the cap off just because it wouldn't stop over pressurizing the reservoir and over flowing.

 

I was thinking the hydro boost might be contributing to it. It doesn’t dump a lot of fluid but it’s making a mess. It is still between full and add on the cold side of the stick. the new pump came with a cap and dipstick.

 

I’ll give that a try thank you.

 

I just lowered the level by 1/2" - problem solved.

Before I changed the cap 3x to no avail.

ATF expands quite a lot when hot, there is a vent inside the cap to release pressure, it leaked out this vent.
There is no benefit from having that Reservoir filled al the way to the top, suction line is almost at the bottom of it.

Try this first before you start ripping apart the whole system all over again.

 

We are camping this weekend so I’m going to monitor it and see how low it gets. I’m gonna try and vacuum bleed it and swap the old cap first when I get home. I thought it was weird I would get to my destination and the reservoir would be covered in oil and the fluid wouldn’t be foaming or overflowing when I take the cap off. I’m not getting any pump noise and the brakes and steering are working well. I was thinking the brake booster might be surging the reservoir somehow but I don’t know. I might still have air in a line so if I do hopefully the vacuum bleed will get it out. It’s like I’m getting a big bubble that overflows it quickly. It doesn’t happen on short trips though.