ok here's the deal, guy came over with a mx 470 89, rings and piston on clutch side where scrap so i put a new set of pistons and rings. reasembled the engine and now it wont stop overheating. if you start it and leave it idle for 5 min it would reach 80. when ridding in snow it could take up to 15-20 min before you get to 80. Drained out the cooling system, still overheating but i noticed its more on the clutch side that gets hot ! now i dont no what else it could be ? *any sugestions...

Might be because of new pistons. My sled did that for 1 tank of gas after my new pistons were installed and it's now running alot cooler, Lack of snow doesn't help either http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/confused.gif

When its running does it pressure up the coolant tank, indicating a pinched head o-ring? If thats not the case, try raising the front of the machine HIGH to bleed the heat exchangers.

check the thermostat.

Did you bleed the cooling system properly?

i lifted the sled almost in a 90' angle to blead the coolant system *and a lot of bubbles were comming out and the temp was going down but when we put the sled back down the heat came back up ? *the termostat is brand new with the pistons. *I noticed the the head gasket had extra holes made in it as if the guy wanted more prestone to pass ? ( im talking about the thick rubber one) Il take the head back off to check the o-rings and see if i cant find anything.

DanR is there coolent flow? are the heat exchangers getting hot?

i was not able to get it started this morning to bring it in so i took the plugs off and the one on the clutch side is full of prestone so im pussing her in and taking it apart. il be back after !

Had the same problem with the same engine in my machine last winter. *Was the clutch side cylinder oring that was leaking. *(Had the same over heat prob.) Just make sure that you tear it all the way down to be able to check the crank bearing on that side (antifreeze kills bearings). *I ended up finding out the hard way after replacing all the gaskets and orings and putting on only another 40 miles when the bearing went on that side due to the antifreeze and threw the rod right through the case, making then a rather expensive boom...... http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/smile.gif *(new crank, rods, pistons, case.....etc)

~Matt

Took it apart and the o-ring and the one around the cyl was finished. got a complete set of seals and now everthing is working great ! did not go down into the crank *to check i only saw your post after i got everthing back up and running !

anybody else have a crank failuer because of the prestone ? *i realy dont want to open it up again. *http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/confused.gif

It sounds like you know how to bleed the cooling system, but be sure because if the system isnt bled properly you will cook the o rings again, and that may be the least of your problems.

tb2, what i did was lift the front as high as i could and took the rad cap off and let the sled idle for a few min untile there were no more bubbles comming out ! then i *put the sled back down filled up the antifreeze and put it back up just in case there was still air in it. im not sure if this is the correct way to do it but is has worked for me in the past. If you have another way i would be happy to try it out . *http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/wink.gif

hey dan how are u: ok i think u did cook the o rings and this lead to the coolant leaking out. i dont lift the front of my sled at all. just give it time . now what pistons and rings did u put in ? if it was wisco that might be your problem. it almost sounds like the engine is too tight let me what else uve tried or what eles happened

Hi Machz im great ! ok the pistons are kimpex ( the guy has no money) Took the sled out for 2 hrs today no problem and then the water pump seal started leaking but i did not change that one and it is made of silcon so im gonna replace it tommorow !