08 yz 450 using coolant

5 replies to this topic
  • pbonics

Posted February 10, 2011 - 06:16 AM


08 yz 450 using coolant, its not coming out of the overflow, it's not coming out of the top of the head? replaced piston and used a cometic Gasket. I have heard its best to use a stock gasket. could this be my problem and should I use a stock gasket? thank you

  • grayracer513

Posted February 10, 2011 - 07:32 AM


You are more likely loosing the coolant from the water pump. This can be quite difficult to detect, since the coolant is nearly transparent in small amounts like that, and it may only leak while it runs. Check for a leak while it runs by swiping a finger across the leak escape hole under the pump, and/or check the covering of the pressure vent line from the crankcase cover for the smell of antifreeze.

When servicing the pump, check the balancer shaft bearing:


  • primerib108

Posted February 10, 2011 - 07:44 AM


That is a great link. I just finished replacing the oil/water seals for the impeller shaft.....guess I know what to look for if I have a repeat failure.

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  • pbonics

Posted February 10, 2011 - 08:35 AM


thanks fellas, I haven't noticed any leaking but a definite smell of anti freeze. how about the head and/or base gasket idea? Have you heard that oem are better match up than the cometic gasket?

  • grayracer513

Posted February 10, 2011 - 08:53 AM


No, Cometic is a good product. The head bolt torque procedure is difficult for some to follow; are you sure you did that right?

My money is still on the water pump. I've been down that same road, and the leak at the pump was nearly imperceptible other than the residue on the vent line smelled of coolant.

  • motox100

Posted February 15, 2011 - 11:42 AM


I had a problem with the cometic gasket kit that came with my Moose Racing piston kit. Same deal, using coolant and could smell it as well. Pulled the head/cylinder off and could see where it was pulling in/burning coolant. Re-Assembled with a OEM gasket and no more problem.

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