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  1. #1

    04 MSX thermostate change NIGHTMRE or am I dumb..

    Who's do a thermostate change on a MSX. What needs to be removed? What holds the thermostate housing together? Does the whole pipe have to come out under injection?
    Thanks for any short cuts to Thermostat..

  2. #2
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Based on your previous posts, I'm guessing your talking about the MSX 150. (140 had different engine)

    So, yeah... the T-stat is located on the rear end of the 'water pipe' tucked behind (against the engine) the intake manifold.

    See MSX 150 service manual diagram on page 4.12.
    ASSEMBLY NOTES (from service manual)
    Water Pipe Fastener Torque: 7 ft.lbs. (10 Nm)
    Thermostat Opening Temperature: 180_F / 82_C
    Snap ring chamfer faces outward, towards rear of engine.
    Always use new o--rings during installation and reassembly.
    Elbow pipe points down and toward the heat exchanger.

    ***Based on what I can glean from the service manual... I've not personally done this... I'm just removing the entire engine on mine***

    It looks like to get at the elbow pipe that holds the t-stat, you have to drain the coolant, then move the coolant overflow bottle out of the way to gain access. Then remove elbow/t-stat housing from hose that connects it to the heat exchanger below it. Then you should be able to get at the snap ring that holds the elbow/t-stat housing to the water pipe. Remove snap ring then pull elbow to the rear. Should pop off... there is an O-ring that seals it. See 'Assembly Notes' above about it.

    I hope your t-stat is your issue with overheating... but if not... it could be a stripped plastic gear inside the water pump like my MSX150 had... which caused overheating too. That, unfortunately, requires you to pull the engine to get to the water pump.

    Good luck.

  3. #3
    Thanks. It does squirt fluid back into resevor when I hit 1000 RPMs but not at idle.

  4. #4
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Yeah... that doesn't sound right. But I can't say from experience. I've never had my MSX150 running yet.

    I would think there would be some flow at idle... and more flow at higher RPMs... since water pump is drive off engine.


  5. #5
    Let me give you a history of my unit. 7 years ago this unit recieved a new $6000.00 warrrenty motor straight from Polaris. It sat for 6 years with factory motor. The motor Hut a polaris dealer had this problem after it was installed. They quit Polaris right after they installed motor and could not get a qualified mechanic to figure this out. The new motor and the way she runs and rides is why I do not want to sell it although I've been tempted anyway. My question:
    Would a new factory motor included a new water pump?
    Would it of been part of the entire motor package?

  6. #6

    Join Date
    Apr 2010
    Stamford CT
    Due to the modular assembly of the Weber MPE used in the ski, my best guess is yes. A new engine would include a new water pump as it is buried behind the front cover. However, we are talking about Polaris and who knows why the engine was replaced in the first place and how many parts were recycled from the original engine. Given the fact that the ski has been sitting for 6 years, I would start with the t-stat. I had to rebuild my ski's engine last summer and it is a project.

    I would add moving the oil tank to gain access to the coolant expansion tank bolts and thermostat helps. There was enough hose for me to just unstrap my tank and lift it up to shift it toward the exhaust side of the ski. That snap-ring will be a pain. Having a good set of tools will help (I didn't, cheap Autozone junk.)

    Another suggestion would be to verify that all of the cooling hoses are routed correctly and connected in the proper locations before tearing too much apart. Between the anti-freeze loop and the fresh water loop, there are a lot of connections and opportunities for a hose to be pinched, kinked or not connected in proper order.

    Click image for larger version. 

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  7. #7
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Yeah... a new factory motor... I can't see how that would have a bad t-stat or water pump. Even if the new motor was only a short block... the folks putting the water pump back on wouldn't miss a broken water pump gear. I guess a bad t-stat could slip unnoticed. But what are the odds.

    I guess it's also possible that it was all good, but in the dealerships attempts to test out the new engine, something else broke.

    Sorry for your troubles. Hope some more experienced folks chime in here with their thoughts too.

    Good luck.

  8. #8
    Good stuff!

  9. #9
    Once you get the almost impossible C Clip off (took 2 2 hour mornings) Now the Elbow seems stuck. Does it just pop off? It is soft metal so I do not want to ruff it to much. The diagram is unclear. Maybe screw off? Thanks

  10. #10
    Finally got to Tstat. Put both new and old t stat in boiling water. The old opened much faster than new. Probably not good news on overheating??? I'll put new one in anyway.

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