The boiling point of anti-freeze is higher than water from my understanding. When anti-freeze gets near or above the boiling point the pressure in the radiator increases. When the pressure get over a certain amount, anti-freeze is pushed out the radiator breather hose. How common is this? I noticed a fair amount coming out of mine yesterday during a practice run. Is my bike over heating? If so what can cause overheating?

It's common when riding slow, tight trails, to occasionally overheat a little bit, due to the lack of air movement going through the radiator(s). It's also common on YZf's to overheat, if they are left at idle for several minutes. (you really should not let a YZF idle more than about 3 minutes......)

My 2004 Yz450f, would occasionally spit out a bit of coolant on a hot day, when riding slow, tight trails. I drained all the coolant out, flushed the system with Distilled water (I let an entire gallon just flow through, to clean out any residue) and used "Engine Ice" as a replacement coolant. My bike has never again spit coolant, since using "Engine Ice".

p.s. remember before every day of riding, to make sure the coolant level is at it's proper level. I've noticed after 2 or more rides, that the coolant level does drop a small amount.

If you fill the radiators full to the top (as the manual actually tells you to), you will have coolant being exhausted from the vent as it expands, until it finds the level at which there is adequate room for the hot coolant. When it cools off, inspecting the level will show it somewhere around the tops of the tubes. If you don't add more, no more should be blown out.

how much has your temp changed? are you warming it up too much? do you race the throttle to get it to warm faster? have you changed your jetting if you've been riding at a different climate or temp change?

if any of this sounds familiar and you're regularely puking coolant, check your waterpump cover for leakage. i'd check the shaft for scorring; it'll slip and score when run hot for extended periods, even before the seal blows.

if any of the above things sound familiar, drain the coolant and do as Flintlock28 said and drain and rinse with distilled water; then check your waterpump seal and shaft.

if you sort this out, get a temp gauge from Pro-Circuit that'll let you keep your bike cool at any temp. i've been using Engine-Ice for a few years and it works good; look at Maxima Coolanol...it's supposed to work good too.

hope you sort it out.

Thanks for the clarification Gray, No wonder I'm having to "top her off" by following the Manual's height recommendation.

Thanks guys. Your input really helped. :worthy:

Engine ice is a great product. Even if your not overheating, i think you should put it in.

i use engine ice too and have no problems

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