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Discussion Starter #1 (Edited)
Hey guy's I am new to the ATV world. I have been a mechanic for over 40 years. Mainly import car repair and some motorcycle. In my later years I have been involved with old car restoration in my spare time and now have undertaked a side job for a rich buddy that involves repair of his dear lease vehicles and equipment. At this time he has 3 Polaris sprotsmans, 2 500's, and a MV7 (700). There are also 2 two seaters and 1 four seater that are new and I have not done anything to yet.
On to my question, The MV7 wasn't running due to a bad battery, I fixed that, then it began to run hot (the HOT lamp and CHECK ENGINE lamp came on). I have inspected the coolant level, cleared the radiator of debri (not that dirty), the cooling fan comes on,I have removed the thermostat and done the heated water trick (it works) and it appears that the pump is working cause I see water flowing in the filler neck. When the warning lamp is on I can remove the cap (no pressure) and stick my finger in the warm coolant it is warm not hot. The radiator tanks are uncomfortable to hold on to but not so hot that you cant leave your hand on them. The radiator core is warm (a little cooler that I expected). I have come to the conclusion that this vehicle is not getting hot and the indicator is faulty. Whats your best guess? Is this one of those quirks that come with the ageing ATV or do I have a one of a kind?
 

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Discussion Starter #3
Thanks Russ, The cooling fan opperates ok but, the Hot lamp comes on along with the Check Engine lamp and I really don't think it is overheating. I have had the oppertunity to read several other posts on overheating and it seems that other people have had issue with the engine temp. sensor that tells the Hot lamp to come on. I will test it tomorrow and will inspect some other possibilities as well. Thanks for your post.
 

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Huuum not much response.
I don't normally like to post up with things I don't feel are going to be a help but you seem to want responses so here goes. You seem to have covered most all the bases with your original post. My only thought on first reading it was a faulty temp sensor and Rus hit on that. He is one of the most experienced and most generous with his knowledge on this site so I would look at what he says. I haven't had any experience with over heating (I am knocking on wood with crossed fingers) so I cant tell you what I did. Good luck and when you figure it out post up and let us know what it took to fix it.
 

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Discussion Starter #6
I went to the lease today and pulled the coolant sensor from the head. (the MV7 dosn't have a sensor in the radiator) My Volt ohm meter had a weak battery so testing was not going to happen today. I brought home the sensor and am headed to the WalMart in the morning for some AAA batteries and will test it after work. Hell I have it out I might just go to the dealer and get a new one. I have a service manuel that has spec.'s for the sensor at differant temperatures. Weird that this vehicle has no sensor at the radiator, the coolant sensor must be a two fold opperation telling the fan when to come on and then the Hot lamp to illuminate if the temp. gets to high. HUUUUMMMM???? Worried now that this could be an ecm issue and not just a sensor. Crap I am not going to sleep tonight worring that I could be wr--wro--wron--- MISTAKEN! LOL good night all.
 

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The 500's have the temp. sensor(hot light) on the left side of the block,about halfway up the cylinder block,almost beside the thermostat housing. The switch that tells the fan to come on is usually on the right side of the radiator.
I have no knowledge of the 700's.
You can look up parts on your or any dealers part fiche to give you a better idea.
 

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Discussion Starter #8
Called the dealer today and he said that the MV7 only has the one sensor just below the thermostat housing. I performs both functions, at a certain temp range the cooling fan is turned on and if allowed to heat further will then set off the Hot(check engine) lamp. My sensor is out of range acording to the test in Clymer repair manuel and I have ordered a new one.
 

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Discussion Starter #9
Ok guy's and gals, I removed the sensor and ohm'ed it at rome temp of 70 deg. F. and it was out of range. Rather than make a mess of my kitchen using hot OIL to test the sensor with I went to the dealer and ordered a new one. I was right the sensor was lieing to me. With the new sensor in place the fan comes on and no HOT lamp after 45 min. of run time. IT"S A FIX!!! Thanks for the input and keep this in mind. My high school shop teacher use to say "If it ohm's good it is good"!
 

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Great to hear. Thanks for posting up your results.
 

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One question since I'm running into the same issue. Did it fix your pressure problem?? Seems to me that the sensor wouldn't fix that? I called a dealer today that I usualy do business with and they mentioned it's probably the filler neck on my since it over heated and expanded it to the point where it won't build pressure.
 

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Discussion Starter #12
Sorry for the late reply. The low pressure problem was not an issue. What I was tring to say was that the engine hot lamp was comming on but the system didn't have any pressure like an overheated system would. In answer to your question the sensor was defective and I was getting an over heat signal when in fact it was not hot.
 
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