Jump to content

Vote for Featured Tractor of the Month!
Garden Tractors and Parts on eBay

- - - - -

Sundstrand hydro

  • Please log in to reply
4 replies to this topic

#1 jacreech OFFLINE  


    New Member

  • Member
  • Member No: 7696
  • 3 Thanks
  • 12 posts

Posted April 14, 2016 - 02:44 PM

Greetings, friends.


A couple of years ago I started a short thread on my Bolens Sundstrand series 15 hydro rebuild.  A couple of you responded and offered good help.  I see that Bill Petenpole has also posted an excellent and detailed rebuild guide on this site - I may need to use it.  


A few years ago I rebuilt my hydro, but it only ran well for one season.  After that I sent it to LJ Fluid Power in Delton MI for a rebuild. They had rebuilt it once before.  This time it only ran another 120 hours or so.  I hesitate to spend the big bucks to have a rebuild done again, but on the other hand hate to put my old Bolens QS16 out to pasture.  I have rebuilt virtually every component on this tractor, and even the K341 engine only has about 300 hours use.


With such short periods before going out, I'm wondering if I am somehow getting contamination into the hydro from my differential (wear particles?) or attached mower lift hydraulic cylinder.  Has anyone had any success in flushing the fluid a couple of times, in case I only have a clog somewhere?  My free wheeling valve was in good shape with the last rebuild, but I plan to check that again to make sure.  I don't have any noticeable leaks.


Any suggestions?





Winchester VA

  • shannonwj18 and kaseyhs69 have said thanks

#2 Billy M OFFLINE  

Billy M
  • Senior Member
  • Contributor
  • Member No: 15999
  • 498 Thanks
  • 455 posts
  • Location: Carlisle, OH

Posted April 14, 2016 - 03:53 PM

This is surprising.  Those Sundstrands are pretty bulletproof.  How are you using your tractor?  What filter are you using?  What oil/fluid do you run?  Do you see any foreign matter in your oil when you drain it?

  • blackjackjakexxix, jacreech and Paulgo have said thanks

#3 Paulgo OFFLINE  

  • Senior Member
  • Member No: 68759
  • 652 Thanks
  • 416 posts
  • Location: Sault Ste Marie, MI

Posted April 15, 2016 - 12:28 PM

Is your freewheel pin nice and tight?


I agree with Billy M. These are pretty much bullet proof. A couple of mine have over 1000 hours on the meter. Never had anything worse go wrong than a front seal. If yours has had two rebuilds and it still isn't right, then it is time to pick up another Q series tractor for parts-- and swap trannies. They are all over and can be had quite cheap when the engine goes out. Just my opinion.



  • WrenchinOnIt said thank you

#4 jacreech OFFLINE  


    New Member

  • Member
  • Member No: 7696
  • 3 Thanks
  • 12 posts

Posted April 16, 2016 - 09:20 AM

Thanks, Billy M and Paulgo. 


LJ Fluid Power has done three rebuilds on this hydro over the past 20 years, and they have a good reputation.  So I am wondering if I might somehow be getting contamination into my system.  A few years ago I did rebuild my transaxle and mower deck lift cylinder - but carefully flushed/rinsed those components several times and think they were clean.  


I have always used the recommended non-bypass hydro filters (Wix 51410/ NAPA 1410 or Bolens) and hydrostatic fluid.  I plan to change my fluid and filter today, even with only 120 hrs. use on them.  I also have a pressure gauge and will check running pressure.  The hydro usually runs a while, then gives out.


Thankfully I have a zero turn to mow with, but want to get the Bolens running again - especially since I have rebuilt virtually every other system on the tractor and it is in top shape.  Even a K341 with only about 300 hrs. on it.


Thanks again,


#5 jacreech OFFLINE  


    New Member

  • Member
  • Member No: 7696
  • 3 Thanks
  • 12 posts

Posted April 17, 2016 - 08:01 AM

A quick update on my hydro:  I ran the engine for 15 minutes and engaged the transmission forward and reverse.  All was working well - good, strong power in both directions.  Then I drained the fluid and installed a new filter and new fluid.  There were some metallic flakes on my magnetic drain plug, so I'm guessing I had a clog from having rebuilt my transaxle two years ago.  All is good now.  I drove the tractor all over my yard and up and down my street at various speeds.  


The tractor also had no trouble starting after sitting for a year plus.  My battery is still at full charge after running the tractor for a half hour and all systems are full speed ahead.  


Thanks again for the helpful advice.