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  1. #1

    2003 MSX140 No Thermostat?

    Hello everyone, I am rebuilding the motor in a non-running msx140 that I bought and went to service the thermostat and housing, upon disassembly, I realized that there was no thermostat. But there appears to be a type of PVC looking tube with 4 holes in it where the thermostat should be. Any advice/knowledge would be appreciated. Thanks.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Post a clear photo of this piece.

  3. #3
    Here is all that came out of the thermostat housing when I took it off. Also, some closeups of the piece.





  4. #4

    msx 140 no thermostat

    not sure what the plastic piece is? i have a 03 msx 140 that i run with out the thermostat or the plunger. i have ran it this way for 3 yrs. no issues at all. i feel better not having them in there! less chance of blockage. my guess on the piece is they were worried about to much water passing through and fabricated some kind of restricter?? some guys feel very strongly about running thermostats and some do not. this issue has been debated on here before. all i can say is that i have not had any problems and i do not worry about it! if i ride in the early spring or late fall when water and air temps are cooler i have always idled around for several minutes to let motor warm up before rideing faster. i have always done this with all my skis not just the polaris. hope your rebuild goes smooth!!

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Interesting

    I take it that short white tube piece was located below the plunger spring?

    My guess is that Polaris revised the pressure by-pass plunger design, but didn't update the parts diagrams.

    Under the spring, the white piece would increase the spring tension, and therefore increase the water pressure (engine RPM) at which the by-pass would open and allow increased cooling water flow. Below that pressure/RPM threshold, water would be only flowing through the thermostat. I would expect that the thermostat was installed at the factory.

    As engine RPM rises, the pressure bypass spring compresses, allowing more water flow (similar to when a thermostat is actually present).
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    Last edited by K447; 05-17-2010 at 12:09 PM. Reason: Initial seculation countered by better info :)

  6. #6
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    plunger

    from what i remember on the msx water bars i got the white piece is used to shim-increase spring pressure making the t-stat control water temp as much as possible.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow Reversed thermostat housings on some 1200 engines

    Additional thermostat info

    The 2002 service manual says;

    If low end performance of the watercraft begins to deteriorate, and the jet pump intake area is free of debris and weeds; or if the overheat alarm sounds, the thermostat pop off assembly should be checked for debris and cleaned.

    Also inspect the thermostat pop off assembly if the watercraft has been stored for more than 30 days or has been used in salt water.
    To do this, use a 3/16 (5 mm) Allen wrench and a flat screwdriver.


    The 2001 service manual says;

    Carbureted Models feature reversed Thermostat housing assembly.
    DFI models are not reversed.

    Reversed thermostat housing on;
    2002 Genesis, Virage TX
    2001 Carburetor models with 1200 engine have reversed housing. Ficht models do not.



    Cooling Check Valve
    The SLX, PRO 1200, and Virage TX have an inline check valve between the injector fittings. During maintenance, verify that the valve is clean of foreign material.

    The check valve will pop-off at 3.5 psi.
    Use a Mity Vac pump to verify that the valve releases at 3.5 psi.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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