Roof stuck in final stage when opening

[pabohoney1]

2011 Z4 sDrive 35is ~105K miles.

Problem: When opening the roof, everything works fine until the final stage (back glass folded on top of roof, clamshell open). The pump sounds like it's attempting to lift the assembly, but can't. I can even hear the seal along the top of the windscreen separate, so it's TRYING to move. With no assistance it will eventually error and blink the button LED red. However, if I assist and lift the roof assembly a little, then it will complete. Closing the top is fine, everything works as normal.

Things I've checked:
- The hydraulic fluid level is at the MAX line, and it's never been filled so I think that eliminates any chance of leaks.
- Sensors/switches seem to be working. I don't get any codes when checking with Rheingold (ISTA/D), just an error on the car screen saying "Hardtop" or something like that. Also, a few years ago I replaced the section that commonly breaks on all the wires in the roof. I had 2-3 that were broken/ready to break so I just did them all.

My guesses:
Gas struts: I've never replaced the gas struts for the roof, but every thread I've read doesn't indicate that these assist with opening/lifting the top, only with dampening the close motion.
Internally leaking cylinders: I'm skeptical about this because closing the roof works fine. I suppose the seal could be failing in one direction and not the other but it seems unlikely.
Dying pump: the pump sounds normal I guess, but I'm not really sure how I'd know.

I can get a video of the problem happening if it would be helpful. I searched and read through a bunch of threads but didn't find any that matched what I was seeing. I've dealt errors regarding broken wires, those trigger pretty obvious codes. I'm not sure why no codes are showing up for this.

 

[RobbiZ4]

Gas struts: I've never replaced the gas struts for the roof, but every thread I've read doesn't indicate that these assist with opening/lifting the top, only with dampening the close motion.

I disagree: the two gas springs in the lower roof area actively assist in lifting the roof assembly when closing. When opening the roof, they only provide damping as the assembly lowers into the trunk.

1) Was the front locking system unlocked?
2) You could check the two brass valves on top of the hydraulic pump. Take a 6mm allen key and try to fasten it a bit more, but don't destroy it!

 

[pabohoney1]

I disagree: the two gas springs in the lower roof area actively assist in lifting the roof assembly when closing. When opening the roof, they only provide damping as the assembly lowers into the trunk.

Apologies, I meant dampening the motion as the roof lowers into the trunk. They don't assist with lifting the roof is what I meant.

1) Was the front locking system unlocked?
2) You could check the two brass valves on top of the hydraulic pump. Take a 6mm allen key and try to fasten it a bit more, but don't destroy it!

1. Yes, it unlocked and acted like it wanted to move. Like I said, I could assist it with some lift and it will open, so it's not stuck locked.
2. I'll double check this, that's a good call out.

 

[RobbiZ4]

They don't assist with lifting the roof is what I meant.

They really do with their 2x 800N force.

The 3 Series E93 use 2x 1,300N gas springs. In these older models it can happen that the much heavier roof package tilts in the trunk and can no longer be lifted.