2003 YZ250F radiator leak

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Sep 3, 2007
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#1
I was out racing last friday night, and after my first moto, I noticed my radiator was smoking. After inspection, I noticed that some coolant had leaked out of the left close to the top. So I bought a bottle of Engine Ice, and poured it in till the coolant was a little over the fins. I ran it maybe 200 yards, and I noticed the exhaust header was glowing orange for a couple inches out of the motor. I took it up to the mechanic guy, and we took the spark plug out, the air fuel mixture was perfect. Not to lean, not to rich. So I decided to run the second moto, and on the line I noticed the header was glowing bright orange for about 3 inches on the header after the bike was on for about 45 seconds. Moto went allright, no bike problems. Then after the moto, while it was still running the header was hardly glowing at all.

I had another race the sunday after, so all I did was add coolant after each moto (a little bit over the fins), although I think it is just going out of my overflow, because after the second moto the radiator didn't look wet at all, like it did during practise. But I highly doubt it would all of a sudden fix itself..

So my questions are,

Is their an easy way to find a leak in a radiator?

One person said that its okay to mix coolant, and another said I should dump it all, and add only the Engine Ice, or normal coolant. Will it be okay mixed?

Is their an easy way to fix a leak in a radiator? I was told JB weld works, or I could possibly soder it together.

Or should I just buy a new radiator half?

And will it hurt it at all running it like it is untill I have time to fix it, as long as I keep the coolant level good?

Sorry for the Long post, and thanks for your help.

-Cabot
 

BSWIFT

Sponsoring Member<BR>Club Moderator
N. Texas SP
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#2
The glowing header is common and you shouldn't worry about it. How low is your coolant level after a moto? What was the temperature on the days this occured? The JB weld is really just a quick fix but depending on the location of the leak, it could be permenant. As for finding the leak, warm the bike up and lean it toward the side you suspect is leaking. Forcing the water to one side or the other will maximize the coolant level in that particular radiator and if it is leaking you should find it. Fixing it permenantly is a matter of where the leak is located.
 
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#3
The Coolant was only like a half to quarter inch below the fins. And the temperature was about 70 degrees Friday night, and about 60 degrees during practise on sunday, then around 75 for my motos.
 

oldguy

Always Broken
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Dec 26, 1999
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#4
Cabot the heaaders on the 4 strokes will turn cherry red real quick if no air is moving over it. On the line my son will be one of the last to start his bike to minimize this heat buildup.
As far as radiator repair there are sveral shops around wis that repair aluminum auto rads and most should be able to cure your leak.

If you insist on using engine ice according to their directions you must keep it straight with no water or anti freeze coolant mixed in. I would say call around to local Rad shops and ask if they work on aluminum and get them to fix it. Final resort send it to Mylers in Utah. The cost of shipping and repair is less then the cost of a new one.
 
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#5
Set you up a pressure checker for the radiator. An easy way is to have an extra radiator cap and find you a bolt in type of valve stem (typically used on trucks and other industrial equipment tires). Drill and mount it into the radiator cap (I have also seen valve stems solderered/brased into the caps also or something similiar). Make sure you have a good seal and water/mix in the radiator (green is easier to see). Slow increase the pressure to the max rating on the stock radiator cap. Don't go too much over or you will cause yourself other problems (max?). You you should see the leak if you have one. It will hold the pressure if there is no leak.