ski doo overheating problem - Snowmobile Forum: Your #1 Snowmobile Forum

formulaIII800 · 09-30-2008, 10:33 PM

I have a early ninetees ski doo formula mx with a 467 in it. The sled is my beater that I take around the yard. It has always been a reliable sled until this overheating problem it just started having. We were told by a mechanic that if you take out the thermostat that sometimes it will allow the antifreeze to flow through the engine better. We took it out and the sled still overheats after about ten minutes. Then he said try replacing the head gasket and o rings. We did that and checked the bottom end of the engine as well for leaks. After doing all this it still doesn't seem to make a difference. My question is what do you guys think I should do now? I was thinking that I should test the water pump to see if coolant is flowing through the block? They do have water pumps right? Is there any easier way to test this then unbolting the top coolant hose off of the engine and then running it. I have tested my car this way before and it can make quite a mess....lol.....Thanks alot

**RJ Gleason** · 09-30-2008, 10:36 PM

You probably have an air locked heat exchanger.
Put the front of the sled up high enough to be above the rear heat exchanger and run the engine up to temp to make the coolant flow. This will allow the air bubble to move out of the rear of the system and then you can top off the tank as needed.

**smallengineguy** · 10-01-2008, 06:07 AM

Along with what RJ said, you should be able to reach up under the tunnel after 5 or 6 minutes and the heat exchangers will be warm. If they are not, they need to be burped like above, or you have a water pump problem.

formulaIII800 · 10-01-2008, 10:43 AM

alright thanks,ill try it and see what happens

formulaIII800 · 10-04-2008, 09:58 PM

alrite so I lifted the front end of the sled and let it run. There were a ton of air bubbles in it so i just kept running it. I had 2 stop though becuase it was starting to overheat. I am going to do the same process 2morrow until i see it stop bubbling. Hopefully 2morrow it will finish bubbling......ill keep everyone posted with updates

formulaIII800 · 10-07-2008, 10:01 AM

alright so i did as everyone said and tried to get the bubbles out of the coolant. I let the sled run for about forty minutes in the last two days. I felt the rear heat exchangers and they were pretty hot so I figure that I don't have any more air bubbles in the system but the sled still overheats. Anyone have any other thoughts of what might be wrong? the water pumps good,no gaskets are leaking,coolant doesn't have any air bubbles in it, and I took out the thermostat.

jagermiester · 10-07-2008, 11:46 AM

Put the stat back in or at least gut the stat and install the outer ring. You have to have something there for restriction to slow the coolant down so it can be cooled. If the coolant is moving thru the heat exchanger too fast it doesn't have time too cool. How long does it take to over heat? It is still kind of warm out.

JheLrey · 10-07-2008, 01:19 PM

Run cold water over the coolers in the rear while you are working on it, it helps cool things down so it will not overheat.

**smallengineguy** · 10-07-2008, 07:53 PM

Remember if there is no snow hitting the coolers, it WILL overheat!

formulaIII800 · 10-08-2008, 10:37 AM

well this problem started at the end of last season so i know it was gettting enough snow on the exchangers

formulaIII800 · 10-08-2008, 07:20 PM

wait....heat exchangers and coolers are the same thing right?

skidoosledder · 11-13-2008, 10:09 PM

the heat exchangers are like the radiator in your car. if no air(in this case snow) is flowing through/by them, they can't efficently cool the sled down. wait till you get the sled in some powder. that should do the trick

95skidizzle_mxz · 12-08-2008, 08:12 PM

so i got the same problem as skidoosledder, my 95 mxz temp light is coming on, but my exchangers are getting hot and melting snow. i just took my sled out tonight in about 4 inches of snow and after about 10 minutes the temp light came on as soon as i stopped. i thought it was just because i stopped, but as soon as i started going again the light stayed on.

please help me!

95skidizzle_mxz · 12-08-2008, 08:14 PM

sorry i meant i have the same overheating problem as formulaIII800.

sledhead1221 · 12-08-2008, 08:23 PM

sounds like water pump to me

skidoosledder · 12-08-2008, 08:59 PM

I don't know, he says the heat exchangers are heating up. how hot do they get by the way? I can touch mine at the back where it crosses over to the other side under the seat.

95skidizzle_mxz · 12-09-2008, 05:15 PM

I can touch the exchangers with my hand they heat up pretty warm, they were melting snow off of them when i threw snow on them.

stangcruzin · 12-10-2008, 05:45 PM

Mx 470 Was My Frist New Sled.i Had The Same Issue .it Turned Out To Be That The Groove For The O-ring Head Gasket Was Too Deep.the Head Gasket Would Leak.
On Warranty I Think The Dealer Put 10 Pistons Before Finding The Problem.

95skidizzle_mxz · 12-10-2008, 06:05 PM

so what do i have to do to fix that problem just replace the o ring?

stangcruzin · 12-10-2008, 06:09 PM

Have The Top Of The Cylinders Machined,i'm Not Sure What The Specs Are On The Proper Depth.