Coolant problems

[scott33]

I bought my YZ250F used about a year ago. Ever since then coolant has been coming out of the overflow. As long as I keep fluid in it runs fine. But coolant is always spewing out. Jetting is right, radiator looks fine, waterpump is working. Someone suggested head gaskets so I have them on the way. Any other suggestions that i could do?

 

[mmz77]

Nice reply.......................NOT !!!!!! :|

 

[rmc_olderthandirt]

Coolant coming out the overflow means that the cap is not holding the pressure back.

The cap may not be holding the pressure because the cap is bad OR because the pressure is getting too high.

The pressure could be getting too high because it is overheating and turning water into steam, or it could be getting pressurized from a leaking head gasket.

I would start by simply torquing down the head (to specification) and seeing if that helps. It is a 5 minute job and costs nothing.

Since you already have the head gaskets on the way I would try changing them. You might want to run a compression test before you do. While you have the head off you can also inspect the cylinder for any signs of scoring.

If you are overheating then something is wrong somewhere. When the coolant spews out, is it boiling hot or is it lukewarm? If the water isn't boiling hot then you either aren't flowing enough water through the engine or it isn't overheating.

If it isn't overheating, and isn't being pressurized, then it is probably the cap that is bad. Replace it. It is probably the most expensive test but also the least work. If yoru friends have the same bike, borrow their cap and try it.

Rod

 

[scott33]

Thanks for the advice Rod. I have tried different caps so it isnt that. Im hoping changing the head gasket is going to work.

 

[76GMC1500]

Does it continuously spill coolant? It's fairly normal for a system to burp a little coolant the first time you warm it up after filling it.

 

[scott33]

Its always spilling coolant. If i dont watch it it would go dry

 

[76GMC1500]

Then I guess you're on the right track by checking the head gasket. Also, look very closely at the inner seat for the radiator cap, it's the portion of the filler neck just below the hole to the overflow tube. Examine the seat for any damage or obstructions that may keep it from sealing with the cap.

 

[snb73]

Rod gave sound advice. I can only think of one thing, how are you mixing your coolant? Place a "sticker" thermometer one the radiator (cap side) and note the temperature at boilover. Mix the coolant according to directions on the back of the bottle. I think 75% coolant and 25% water will protect you to 280 degrees.

Good luck, Steve.

 

[76GMC1500]

280 degrees at 16-18 psi. Dirt bikes run at a much lower cooling system pressure so they boil over at a much lower temperature.

 

[Patman]

Distilled water and Water Wetter unless you plan on riding at the North Pole in January :)

 

[snb73]

Distilled water and Water Wetter unless you plan on riding at the North Pole in January :)

Agreed, I couldn't remember the probuct name.

 

[scott33]

i dont mix the coolant. i starting using engine ice because it is suppose to run cooler but it still comes out. i am still waiting on the gaskets. i really think its the pressure getting too high.

 

[1BAD250]

the water wetter is masde by red line thats what i use in my bikes and race car use 2-3oz makes a big diffrence & you should get a water temp sticker vary cheep insurance..

 

[scott33]

Good news. I finally got my gaskets in and it fixed the problem. I went ahead and put new piston rings in also and can really tell the difference. The thing runs like a dream and no coolant out of the overflow. Thanks for the tips guys.