07 yz450 coolant leaking issues

3 replies to this topic
  • trevTFD

Posted January 05, 2012 - 08:11 PM


07 yz450....i need help. last week i was in idaho (temp was 0-15 outside) when i started the bike it leaked coolant out the weep hole. when the bike warmed up it stopped. this happened 4 times. came home to so cal. no leaks. went for a ride in gorman. on a real tight trail in 1st gear, when i got to the top and let it idle, it started spewing coolant out the overflow tube. i understand it was prob because the bike wasnt getting air.....so i came home changed the oil and did the air filer. then started the bike to check for leaks. nothing. but as i let it idle to burn the fuel out of the carbeurator, it spewed coolant out for a good 45-60 seconds till the bike shut off.....my question is why is this happening? can i ride in with the bike doing this? thanks in advance

  • bullwinkle289

Posted January 06, 2012 - 06:05 AM


Hi, I've experienced someting similar and it came down to being the radiator cap simply not sealing properly. The water / coolant level would be topped up to the mark but it would spew out coolant intermitently.....got another cap from ebay, flushed out the system and refilled, problem solved! The old cap was not sealing right round on the rubber part allowing fluid to leak past now and again.


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  • grayracer513

Posted January 06, 2012 - 06:48 AM


The leak at the weep hole in sub-freezing weather was probably a matter of the water pump seal being hardened by the temperature. If the bike doesn't repeat that, it's probably OK, but you should keep your eye on it until you're sure. You may need to replace it.

Regarding the boil-over, three things commonly affect this. One is a lack of air moving over the radiators due to low or no speed. You can't run a normal healthy YZ450 for much more than a minute at idle without it boiling from poor air and coolant circulation. Another cause is low coolant level. The system holds not quite two quarts, so any loss is significant. The last one is "worn out" coolant that is old or mixed at too weak a ratio and boils too easily.

The radiator cap could also be weak as mentioned.

  • trevTFD

Posted January 06, 2012 - 11:31 AM


Cool. I will try this. My buddy said it could be a bad impeller. He said to take the cap off and start the bike to see if the fluid is moving at all. Thanks for the responses.

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