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Discussion Starter #1
This is a very common problem with a skidoo sled.  (Mostly 700 - 800 cc engines including the mach.

Have you ever been riding and your on marginal snow.  The gauge starts to climb and it stops just under the red.  Sometimes it might even touch the red but it never really goes in the red.  

It also seems to climb if your not on good snow and doing above 50.

Well it happend to me on My Mach Z and my 600 Grand touring sometimes likes to rise as well.  

So i got some water wetter and it helped but it still climed.

Well it turns out that the position of the gauge sender is located at a very poor spot.  It seems that heat seems to collect there giving you a very poor reading on the gauge.  Also the gauges are not always accurate.  

If you are riding with your sled and the needle is just under the red your sled is still running very cool.  You dont need to worry.  Even when the needle hits the red you are probably still running cool but most dont unless the gauge is inaccurate.  This is proven with a thermal gun that uses infared to test the engine temps.  

At my dealer we tested it on my mach and on a 800 X.  Turns out the only thing getting hot was the temp sensor the motor was running cool with no snow hitting the exchangers just the wind from the spinning track in the garage.  

So if your gauge goes into the red when driving talk to the dealer. But if it just hangs below it you are still in very good shape and you are a long way to go before the needle crosses the red.  

Also just because the gauge is climbing doesnt mean the temps are going up.  Its weird.

If you have any questions just ask.
 

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Good info! Obviously not a good design when they designed the water jackets of the heads. When hot spots occur inside cylinder heads, the coolant turns to stem which does not carry away the heat.

My '98 MXZ 500's temp gauge seemed to fluctuate some times not all the time. I noticed this the first time in northern Ontario. We were running around 65-70 MPH for extended periods of time between D'ville & Hornepayne. Even though the snow conditions didn't change, the gauge was moving up & down quite a bit. Run thru the twisties at 30 MPH and the gauge would just sit where it always did.

I asked a couple of guys and they said it was just the thermostat opening & closing. Would this be right? I would have thought that once the sled was warmed up & moving (getting snow on the exchangers) the thermostat would stay open and the coolant temp should stabilize.
 

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Discussion Starter #3
It could be that the thermostat is opening and closing on your 500.  Once the sled is warmed up the temp should stay in the same place as long as your getting proper snow.  And the way it should be set up is that it should ge more cooling then it needs and the termostat should modulat it.  

That is how its set up.  But the problem is when the gauge goes right to the top and just stops and holds under the red.  Most people think there on the edge of overheating.  But in truth the engine is running cool.  So its either a poor quality gauge or sender or a bad location for a sender.  

I just want people to understand that even when the gauge is peged right at the top there engines are still cool and getting adquite cooling.
 

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I've run into that as well.A thermostat in no way modulates the temp in a engine though.The thermostat only controls the minimum operating temp,the rest depends on the rest of the cooling system.Funny thing that the gauge will read a almost
overheat but it actually isn't anywhere near setting off the old
idiot light
 

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revrnd..the thermostat never opens and closes...ever...it only opens once and stays open untill it cools off to about 40C..then the stat starts to close.
 

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Glad to hear that I have a 99 MachZ & 2001 MXZ 800 and most of the season my gages were right under the red.  Even shut down a couple of times afraid of warping the heads.  Glad to hear I wont need to worry about that.
 

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I sort of figured from my high school auto shop knowledge that the 'stat opens when the coolant heats up and would only close if the temp dropped. When, this fluctuation occurred, we were running on typical groomed snow. We weren't running over icy stretches. In my mind there wasn't anything that I could think of that would cause the changes.
 

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But....if your sled is running on the hotter side of the gauge...I would not completely ignore it...it should run with the needle a bit lower than centre. Even if the gauge is 'off' there is still something causing a heat build-up. Just something to keep in mind....  
 

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I too would be a little leary of saying that even if your temp gauge is almost in the red your engine is not hot at all. Gauges may not be perfect but they are all you have so I'd pay attention.
                  Ryan
 

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RMN2399: Ditto Ryan, I have owned a MachZ as long as anyone on this forum (Dec92) and have suffered through all kinds of cooling system updates, if the heat gauge goes close or into the red I shut it off to let it cool down. I have seen the results of ingnoring it, and its very expensive. Dino
 

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On my f-3 800 it is almost allways just below half on the gauge but later in the season the trails become very hard packed and icy, that is when it starts to go up to just under the red. I allways jump off the trail and find some soft snow, and the needle drops right away. I've allways been scared to let it clime to high, so if I can't find soft snow at the time I would just shut down and let it cool.
 

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neither one of my Mach's 99, 2000 has ever went over 1/2 even on farely warm days.
 

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I have found that on my 700 triple if I ride slow for any length of time the gauge heads for the red zone but as said earlier it never goes into the red, I found the faster you go the cooler it runs even in warmer ambiant temps.
 

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On my Flll I discovered NO thermostat!! I rode this weekend on low snow conditions, it got so hot [just in the red] that by common sense I pulled over and watched 1/2 gallon of anti-freeze boil on the ground! After a trip to the dealer for a $30.00 stat and $8.00 worth a antifreeze, I was on the go again. This sled has never seen such cool temps until now [1/4 off the peg]. You see, without the stat the coolant flows so fast through the exchangers it cant cool properly [like a restricter]....
 

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So what you are saying is that your F3 came from the factory without a thermostat but you were able to buy one and install it?
 

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I bought it used. The dealer said it should have one.
 

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I was hoping it was a cooling system upgrade that ski-doo had, I looked at ronnie's on-line microfiche and my 700 doesn't appear to have a thermostat in it.
 

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Discussion Starter #18
As much as common sence is telling you to worry about the gauge going close to the red.  The thermal gun says diffrent.  I had it hang close to the red but not go in the red but i still got worried.  Thats when i went to the dealer and complained.  We found that the gauge was total crap and wasnt accurate at all.  But we also found that the only time it was accurate was when it did go in the red.  

But if it was just under you are ok.  I dont know about you guys but 5 sleds i ride with 2 are mine and 3 others all had this problem with poor snow conditions.  According to my dealer almost everyone in my area has this problem because of the snow.  

The problem is also on the series 3 engine.  The gauges were ok on the rotary engines.
 
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