426 overheating??

1 reply to this topic
  • matt04xr250r

Posted October 24, 2010 - 07:09 PM


I got an 01 yz426 and recently I changed my coolant out with engine ice coolant and it ran great when it was first put in. But now I've put around 15 or less hours on it since i replaced it. Now about every time i ride it it seems to be low on coolant so i fill it but then it seems like it overheats and it comes out the overflow. I talked to my local yamaha dealer and he said something bout a sensor on the radiator. i looked briefly but didn't see anything. but he also said its very unlikely that it would be the water fan. I don't know if i need to replace the coolant again or if it just has too much coolant in it or what....

If any ones had a similar problem let me know what u did bout it and how to fix it....
I also do a lot of woods riding and was at a friends doing slower riding when i first noticed it. but it was a colder night a couple weeks ago in an open field when I rode and it still did it.

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  • brentn

Posted October 24, 2010 - 07:58 PM


The rads when filled to the top will always displace a particular amount of fluid to make room for fluid that is hot (hot fluid is larger in volume than cold fluid). You will never ever be able to keep your fluid topped right up to the top of the filler neck after it has reached operating temp.
However there is a point in which the correct amount of fluid is displaced and will no longer displace anymore, this is usually just above the rad core on the inside, but it should never go below.

When my bike reaches 90 degrees celcius it will dump excess coolant out to make room for the increased volume and after it cools the level is just above the rad core. It never drops below this level, and I've never had to top it up anymore after 20 hours of riding.

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