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  •  » Rebuild/reseal of a convertible top hydraulic pump unit

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    2/04/2026 12:18 AM  #1

    Ron68
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    From: Mukilteo, Washington
    Registered: 4/01/2013
    Posts: 1,739

    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

    Rudi
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    From: Stuck in the 50's Welland Ca
    Registered: 4/01/2013
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    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

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,917

    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

    Ron68
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    From: Mukilteo, Washington
    Registered: 4/01/2013
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    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
     

    2/17/2026 6:53 PM  #5

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,711

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

    Ron, I will be expecting a full writeup with pics and videos when you tackle the job.   I have an extra pump system from an 89 Mustang as a spare.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    2/18/2026 10:53 AM  #6

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

    One of the things that got my attention is my 63 Gal takes type A fliud,and the 66 pump take type F.

    Both parts seems like they are the same.   In fact, the lines for the 63 have the same Mustang part #.

    If multiple things can go wrong, the one that will go wrong will be the one that causes the most damage.
     

    2/18/2026 12:07 PM  #7

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,917

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

    Well that's definitely interesting because type A fluid was used primarily by GM.  Were the pump and cylinders outsourced or were they made by Ford?  I'm thinking if they were outsourced Ford may have changed the fluid spec to type F in the mid '60s so everything in the vehicle took type F (PS, auto trans, top parts, etc.).  My understanding of the difference between type F and type A (later superseded by Dextron) is that type F has more friction modifiers.  I had the C4 in my '67 rebuilt in the '90s when I redid the car, and dutifully ran type F fluid, but it had a hard shifts, like it had a crappy shift kit in it (like a B&M).  I heard that once the trans is rebuilt with modern parts you no longer need to run type F fluid, because the frictions are changed to work with regular Dextron, since that's what all the other domestic manufacturers used (now superseded by Dextron/Mercon III).  I changed the fluid to Dextron/Mercon III and the annoyingly hard shifts went away.  

    Now, in a hydraulic system is there a difference in how the fluids would behave?  In other words, did Ford actually change anything or just start spec'ing type F?  I'm not sure on a convertible top (believe it or not I've never owned a convertible) it would.  In a steering system it definitely makes a difference if you run type F vs. PS fluid, but those two fluids may well be far more different than type A and type F transmission fluid.  

     

    2/18/2026 9:39 PM  #8

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

    I did look earlier and 63 Falcons also list type A.    I think I'm going to check 64 , and try to pinpoint the changeover.

    If multiple things can go wrong, the one that will go wrong will be the one that causes the most damage.
     

    2/19/2026 4:17 PM  #9

    Ron68
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    From: Mukilteo, Washington
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    Re: Rebuild/reseal of a convertible top hydraulic pump unit

    MS wrote:

    Ron, I will be expecting a full writeup with pics and videos when you tackle the job. I have an extra pump system from an 89 Mustang as a spare.

    Just ordered the seal kit from NPD - will document the process once i get it done. 

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

    Yesterday 1:26 AM  #10

    Ron68
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    From: Mukilteo, Washington
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    Re: Rebuild/reseal of a convertible top hydraulic pump unit

    Well, I did the rebuild/reseal of the 69 convertible top motor pump. I ordered the kit from NPD. All new o-rings ,new shock mounts, new check balls. It went pretty quickly and was an easy job. The hardest part was squeezing the new shock mount bushings/grommets in place. Reinstalled and ran the top through several cycles to get the air out and make sure the reservoir was full. 
    Sorry about the pictures format. I tried to upload them, but no joy. Copying the embed codes was the only way that worked. (Start at the bottom and work up) 

    https://ibb.co/Rp1P8wzs
    https://ibb.co/PzDCkrzD
    https://ibb.co/qMhjzwXH
    https://ibb.co/0yrMvt5d
    https://ibb.co/WvnNgk26
    https://ibb.co/ch1WswJz
    https://ibb.co/0ynN66FW
    https://ibb.co/7tgL1Fnj
    https://ibb.co/HTC7zVS7
    https://ibb.co/TBRd3HYd
    https://ibb.co/NgVtkQGv
     

    Last edited by Ron68 (Yesterday 1:42 AM)

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

     

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