Cabriolet hydraulic hood issues - wont open until I 'release' pressure?

Hi all,

I have a 93 Cabby with the electric hydraulic roof. Its been working fine until recently. Sometimes if I push the button to lower the roof nothing happens - I hear the motor whine but nothing moves. When investigating this I loosened the valve that allows for manual operation, tightened it again and the electric system worked fine. This has happened a few times. Its like loosening the valve releases some kind of pressure that stops the roof from working?

I checked the fluid levels and it seems fine. When the roof is up the fluid level sits below the empty line but when the roof is down (which, as I understand, is when you're meant to check it) it sits just below the full mark.

Would anyone know whats going on here? Air leak in the system?

Sounds like you could have a leak or just air in the system.

Take the boot cards out and have a good look around the rams to make sure that there's no leaks. Once you leak free then bleed the system.

There's instructions on how to somewhere, let me have a look…

…nope can't find it, I was sure I'd saved a PDF quide somewhere!

It basically involves opening the tap valve and opening then closing the roof a number of times with the filler plug out of the fluid reservoir. I just can't remember the order!

I think chortle posted the guide up last time, perhaps he can help?  

it could be the impeller has cracked on the pump, common problem. sometimes savable with a strip of metal and aldrite. i think i recal reading the mk3 gofl pump impeller fits?

Where is the most common place to get a leak? do the rams go?

On factory fitted rams I've only had issue with the pipe unions leaking. Unscrewing, cleaning the threads and new ptfe tape normally sorts it.

I'm sure the rams can fail though.

Nice one, seems like a nice easy sunday afternoon job! I've got a slow leak. opening the hood works no problem but it needs a helping hand bringing it back over… its fine both ways when the reservoir is full but as it gets low it gives up closing. grrrrrrr
i'll try your fix first… hopefully i don't need rams.