I think I have a problem with the convertible top hydraulic system on my 1969 Cutlass S but I haven’t been able figure it out yet. It seems like the top brackets don’t fold down as far as they use to. The folded down bracket arms don’t lay down flat in the wells on the side of the back arm rests and I think they use to. They stay up about 4” off the bottom and if I try and push them down further the cylinders seem to hold them up. See the photos below. I already bled the hydraulic pump per the Fisher Boby manual. Could this be bad piston seals in the cylinders? Any experience with this problem would be appreciated.

Thank,
Doug

 

A seal issue would present as leakage (internal pressure loss) and slow to raise or not staying partially raised. It appears something is preventing the top from collapsing completely. Are you folding the top material as the top is going down so it lays flat in layers? I wonder if there is too much fluid if it would prevent the cylinders from retracting completely.

 

I tend towards siding w/ Kenneth:
yet, it could be you have residual air in the system (incomplete bleeding).
I notice several areas w/in the bleeding operation which you might simply review to ensure you followed the protocol exactly - maybe bleed the system again. There are several noteworthy areas regarding priming, level of bleeding container, position of power top, cycling the power top properly, NOTE: fluid level should be w/in 1/4" of lower edge of filler plug w/ top in down position and finally IMPORTANT: DO NOT OVER-FILL

Hopefully, running through the bleeding procedure again will resolve the issue.

 

Kenneth & Norm,

I will check the fill level again because I am thinking I definitely left the fill close to the bottom of the hole and not a 1/4” down. I didn’t know that it was that critical. If lowering the level doesn’t work I will try bleeding it again.

Also I do help the top cloth fold out of the joints as the top is going down, but maybe something is still binding? I was also wondering about the inner cylinder piston seals but when I stop the top 1/2 way up it does hold position.

Thanks for the suggestions and I will let you know what I find out.

 

I was going to post merely because our avatars are so....much........alike. But then I thought its been nearly 30 years since I looked at the pump on my old '70 C/S 'vert, but could there be an adjustment on the cylinders or mechanism that causes this?

 

No. I do not believe that to be the case. I have never seen an adjustment mechanism. If there was such a mechanism, it would be identified in the Fisher Body Service Manual and I have not seen such a device.

 

Well I finally got around to working on the hydraulic system again. I checked the pump level and it was a little high but not too bad. I took a couple more syringes of fluid out so it was at quarter inch below the hole. I bled the system again and over ran the cylinders into the down position To get all the fluid out of the cylinders and into the reservoir. I have the arms sitting lower now, about 1.5” off the bottom Instead of 4” and that is the best I think I am going to get it too. The roof itself seems to bottom out there and can’t really be pushed down any further without forcing it so I will have to be happy with that. Thanks for all the suggestions.

Regards,
Doug

 

Doug - I believe that's about the same distance off the bottom as on my '71 CS convertible. My tonneau cover fits snugly over the top and w/o any vertical metal frame protrusion into the tonneau cover. Glad you were able to lower it.

 

Thanks for the follow up post . That's some good information for us convertible owners.

 

Only gm convert I know is a Corvette of those years, and my dad and I operate it via our good friend Manuel.

 

It took me a minute...