I recently had a bad hydraulic cylinder on the 996TT soft top and bought a used one. The top was running fine with the leaky one but the reservoir was low (i.e. below the fill plug hole). I installed the replacement cylinder and now the roof cylinders are not activating at all. If the roof is in the closed position and I use the button on the console, the solid rear cover opens, the flaps open, the windows go down, the roof latch unlocks and the pump motor runs, but it twitches and clicks every few seconds and the cylinders don't move.

I'm running Pentosin CHF 202, which I understand from research is appropriate for this application. There are no visible leaks anywhere. I have the lines installed as shown in the picture, with the blue and red lines installed on the correct sides, the thin copper washers above each line and the thick copper washer between the lines and the pump body. I understand this to be the correct configuration. Does is matter which line from which cylinder is on top?

Note that when I replaced the cylinder, I put both lines of the replacement cylinder into some Pentosin CHF 202 and operated the cylinder manually to get any air out. I then installed the cylinder and connected everything back up, making sure the petosin level in the system was up to the fill plug hole. When I ran it for the first time the cylinders did not move, but with the console button pushed and the motor running I pushed the roof back from its nearly closed position to the fully opened position. The reservoir level went very high so I removed some fluid and then tried again, assisting the hydraulics manually while pressing the console button. Now the reservoir is showing nearly full to the top again, well above the fill hole.

Anyone know what the heck is going on and why this fluid level in the reservoir is increasing?

Note level is quite high

 

I opened the fill screw and there was a ton of air pressure in there. I then reduced the amount of fluid to the bottom of the fill hole and tried again. Still nothing from the cylinders. The top moves easily by hand but no hydraulic power. No resistance either. I let the top go by accident when opening it all the way and it dropped like a stone.

 

My first guess is there is still air in the lines...

As far as the top seemingly dropping back into the car without resistance, that sounds like something may have come loose. I've attached some info.

 

The sequencing of the activities may be OK since everything else seems to work, but there is simply no action on the cylinder at all. I tried putting power directly on the pump and running it with the top both in the closed and the open position. The pump runs but the cylinders don't actuate. I tried with the screw out of the reservoir to see if there was air in the lines that needed to bleed out of there but nothing. There is no evidence that the cylinders are getting any hydraulic fluid. How is it possible that the reservoir has fluid but the cylinders don't get any? This is brutally frustrating.

 

Finally reconnecting to this post in order to close the loop. As noted above, a purchased a replacement cylinder. It came with a complete setup, including a larger pump (from a 2000 carerra, same pump manufacturer) and 2 cylinders, which worked fine. I removed my original pump from the car and bench tested it with the new cylinders. No pressure. I tore it apart and ordered all new o-rings. I rebuilt the pump with the new o-rings and still no pressure. I tore out the old bracket from my car and fabricated a bracket out of the other pump bracket to fit in the same spot as the old pump. Works great and much better quality pump. Pics of the bench test, the replacement pump during installation, and the new fabricated bracket included.