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Subject: 641 Hydraulics

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Tom    Posted 12-24-2020 at 15:22:39 [URL] [DELETE]        [Reply] [No Email]  
  • 641 Hydraulics
  • When I park my 641 for a few days or longer my hydraulic system seems to lose it's prime and won't lift. The only way I can make it work is to blow compressed air into the hydraulic dipstick hole and then put the dipstick back in real fast. Once I do this the hydraulics seem to have plenty of power and works fine. Any thoughts?

    JMOR    Posted 12-24-2020 at 15:42:46 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Air leak somewhere....pump shaft seal always a suspect.

    Tom    Posted 12-24-2020 at 21:27:18 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Thanks- if it is the pump shaft seal, how big of a job is it to change it? Just want to make sure I plan the farm chores accordingly as this tractor is needed regularly.

    TheOldHokie    Posted 12-24-2020 at 23:42:46 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Vane or piston pump?

    TOH

    Tom    Posted 12-26-2020 at 09:30:32 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Piston pump.

    TheOldHokie    Posted 12-26-2020 at 10:57:00 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • The shaft seal is in the gear housing adapter. You have to remove the pumpfrom the tractor then remove the housing from the body (4 hex bolts). It is under spring pressure from the pistons. Dont loose any springs or pistons when you get it loose.

    Once the gear housing is separated you have to unbolt the gear and drive the wobble shaft out from the tachometer drive opening. Then you can drive the seal out from the same opening. Dont damage the needle bearing in the nose in the process.

    Its a bit of a bear to get that seal out. Check to make sure the wobble shaft bearing race is not obstructing the edge of the opening in the gear housing. If it is you will have to remove it as well. The back side of the race is tough to get to so I lay a cold weld around the face to shrink them so the will drop out. Drive in the new seal and reverse the process.

    I would thoroughly check and eluminate all of the oring seals on the hydraulic manifolds before I tore into the pump. I would also replace the needle and wobble shaft bearing and race along with the seal. Expect to spend several hours on the seal job. And there is always the possibility the pump is simply worn internally.

    TOH

    Tom    Posted 12-26-2020 at 17:57:24 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Thanks, this is helpful.

    TheOldHokie    Posted 12-26-2020 at 18:08:36 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Here is some Ford documentation. Unfortunately it is written for the initial version of the piston pump that used a double row ball bearing on teh wobble shaft. That version was quickly replaced with one that used a tapered roller bearing and had a needle bearing on the gear end of the wobble shaft for additional support. The basics are pretty much the same.

    Piston Pump Shop Manual Supplement

    TOH

    Tom    Posted 12-27-2020 at 10:21:49 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • Thanks for this- I'll dig into in next week.

    Ultradog MN    Posted 12-25-2020 at 06:06:33 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 641 Hydraulics
  • I believe only the early X00s had the vane pump.
    Late X00s and all X01s had piston pumps

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