2003 WR450 overflowing coolant and smoking.

Hey everyone.

I have very little mechanical knowledge. My 2003 WR450 has started to have an overflow of what looks like coolant out of a tube in the front of the bike. The liquid then hits the radiator or other hot metal area and smokes.

This happens after the bike sits still while running for about a minute, usually after I have been riding for ten minutes or so.

Is this normal? I mean, it's water cooled so does it need to be constantly moving to avoid this?

Thanks for your help!

My bike gets real hot real quick when its not moving. I always shut it off.

The slightest bit of air moving through the radiators has a big effect. sitting still with the bike running will simply boil the insides of your motor.

Definitely check your fluid levels, then be sure to shut it off or keep moving.

I know I need to find a manual....

But, how do you check the coolant level? I know how to check the oil...Are there any other fluids to check?


Top off the radiators with 50/50 coolant and water and make sure the resevoir is about half full.. If some some reason the resevoir was topped off it wouldn't give the coolant any chance of cycling back and forth from the resevoir and radiators and be forced out the overflow at the top of the radiator when the bike gets hot. Too much coolant would make your bike puke out coolant. Like others have said check your coolant level...


At this point Replacing your radiator cap would be a good idea since this is what controls the pressure in the cooling system.

Does your bike have a overflow reservoir under your rear fender? If so, is the hose that comes out of the rad by the radiator cap (overflow line) fed to the overflow reservoir? If your bike overheats to the point that it boils over, the only place you should see coolant is in the overflow reservoir. No coolant should leak onto the exhaust anywhere.



My 03 WR 450 has only boiled over once and its overflow tube dumps under the bike (just under the pivot point of the swingarm). I belive the cooling system expands in the radiator first then goes to the coolant tank then overflows onto the ground. Can't understand why it overflows onto your engine? Maybe a damaged overflow hose from radiator to coolant tank??

I will take a closer look tomorrow. I have ZERO mechanical ability with dirt bikes but I will look for the hose coming off the radiator area.

How do I check to see if my coolant level is high enough? And, since I don't know what coolant type was used before do I need to drain it all?

Thanks all, I gave you some good feedback for helping me, much appreciated.

With the engine cold the Radiator cap should come off and the coolant shold be full to rim. replace the radiator cap. check the hose to the coolant "catch Can behind the left rear side panel shold be one third full(optimal). this hose should be clear with no damage.:thumbsup:

Check right side engine case for signs of leak. Read stickies at top of this forum and down load service manual if you do not have one.( save you a headache late at night).

Drain and repalce coolant with quality Motorcycle coolant avalible locally. Replace radiator cap with OEM radiator cap.:thumbsup:

If coolant catch can (resivoir) is missing PANIC and post what you found and ask for more help:banghead:

Now Ride like "Hell" and tell us how great it was!:ride:

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