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2/04/2026 12:18 AM  #1


Rebuild/reseal of a convertible top hydraulic pump unit

 My neighbor has a 69 convertible with a leak at the fill port. We topped it off and it puked almost all of it out. I see that there is a kit available - just wondering if anyone had done one?


68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
 

2/08/2026 4:55 PM  #2


Re: Rebuild/reseal of a convertible top hydraulic pump unit

I used a seal kit from NPD a few years back when I re-did my 68 top  mechanism. I had to manually help the top go up and down
The fluid reservoir had a lot of sludge in it, probably never serviced, the cylinders leaked internally and are not rebuildable other than the outer shaft seal.
I completely disassembled the pump and was meticulous in cleaning it putting new “O” rings and the provided parts in it and filled it with type “F” juice.
I ordered new oil lines and cylinders from NPD as well because I didn’t want to do a halfassed job and dig back under the seats when those inevitable snags happen.
I bench tested the rig before I installed it so I wouldn’t have to deal with “in car leaks” and refilling the reservoir and bleeding it in situ.
Hope this helps Ron.


Good work ain't cheap, Cheap work ain't good!
 

2/09/2026 6:44 AM  #3


Re: Rebuild/reseal of a convertible top hydraulic pump unit

Whenever you encounter sludge or trash in a hydraulic system its advisable to replace everything.  I do the same thing with a power steering and/or hydroboost setup.  You don't want to risk the new parts with trash that may still be in the system and will be impossible to flush out, yet somehow will break loose once its back together and trash a new pump, cylinder, etc.  

 

2/09/2026 3:59 PM  #4


Re: Rebuild/reseal of a convertible top hydraulic pump unit

Rudi wrote:

I used a seal kit from NPD a few years back when I re-did my 68 top mechanism. I had to manually help the top go up and down
The fluid reservoir had a lot of sludge in it, probably never serviced, the cylinders leaked internally and are not rebuildable other than the outer shaft seal.
I completely disassembled the pump and was meticulous in cleaning it putting new “O” rings and the provided parts in it and filled it with type “F” juice.
I ordered new oil lines and cylinders from NPD as well because I didn’t want to do a halfassed job and dig back under the seats when those inevitable snags happen.
I bench tested the rig before I installed it so I wouldn’t have to deal with “in car leaks” and refilling the reservoir and bleeding it in situ.
Hope this helps Ron.

Thanks Rudi for the info. I will talk to my neighbor and see what he wants to do about a system overhaul. Probably won't know a lot until we pull the pump and do a teardown. 
 


68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
     Thread Starter
 

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