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Scag hydros slow down once warm

Discussion in 'Mechanic and Repair' started by 97firebird, Feb 24, 2007.

  1. 97firebird

    97firebird LawnSite Member
    Posts: 41

    Hey guys, I have been doing a lot of searching but I can't seem to find what I am looking for. My STHM 61" 3-wheel rider runs strong and the hydros work awesome until they are running for about 5 minutes. So they are strong and perfect, then heat up after 5 min, and are slow and weak. I can hear the pump still pumping, but the speed is dramatically decreased especially when going up hills. My question is...Do I have a hydro pump problem or wheel motor problem? How can I check to make sure? From what I have read it is better to just replace the entire motor, since rebuilding isn't more than just seals. Any input would be appreciated. Thank You.
  2. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    I would try running 50 weight oil in the hydros. Worth a try and cheaper than new hydro's.
  3. Steppenwolf

    Steppenwolf LawnSite Senior Member
    Posts: 403

    A shot in the dark but are your dump valves closed completely?
  4. lucforce

    lucforce LawnSite Member
    Posts: 223

    Belt slippage?
  5. Mr Priceless

    Mr Priceless LawnSite Senior Member
    Posts: 412

    do you know what hydros are?:hammerhead:
  6. lucforce

    lucforce LawnSite Member
    Posts: 223

    I believe that a hydraulic motor is one which would be delivered a viscous fluid under some pressure and at some velocity. This pressure and velocity delivered by hoses, tubing or some other conduit, but first created some other portion of the system (less we defy energy balances); this other part usually defined by the general name "PUMP." This pump must be driven mechanically by some method to produce "WORK." Now, to make this "PUMP" "WORK" let us say that an Internal Combustion Engine (I.C.E.) is used to take a combination of fuel and atmospheric gases and convert the stored energy in the fuel through the combustion process and translate the force of the expanding gases of the combustion process acting on the piston and then translated to a crankshaft via a connecting rod. Of course "WORK" can then be done by the crankshaft of the I.C.E. so long as it connected to say, a "PUMP."

    Now, if only...we could devise some method to connect this I.C.E. to this pump...
  7. XB 2002

    XB 2002 LawnSite Member
    Male, from St.Amant, LA
    Posts: 75

    Boy, That was Good !!
  8. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    very nice lucforce:clapping:
    the only other thing I may also inspect is if you are seeing air bubbles in your hydro tank, you may have a suction side leak in you hydro system. Start by inspecting all your hoses and their connection at the pumps and also at the line into the hydro filter and also the filter itself. I have seen this issue more then once and the filter was the loose and sucking air around the oring. This will at least give you some easy things to check and eliminate before moving on to more expensive repairs. I hope this helps:)
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    [​IMG] :laugh: :drinkup:
  10. jrc lawncare

    jrc lawncare LawnSite Senior Member
    Posts: 420

    Yes!!! A worn out hydro belt will result in slippage, not good when you are looking for maximum output at speed from your hydros. Good post.

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