overflowing from coolant expansion tank

2 replies to this topic
  • 2strokeYardSale

Posted April 22, 2016 - 07:58 AM


I just went through a 2007 WR450F I purchased recently: suspension bearings, valve lash check, carb rejet, etc. Now back together, it is flowing water from the expansion tank overflow line.


I have the radiator overflow line routed into the bottom nipple of the expansion tank. The top nipple of the tank is the overflow hose, which is puking water.


I filled up the radiator past the fins to about the neck and I poured some water into the tank so it was about 1/3 full. Should I have left the tank empty?


During the restoration I pulled the water pump cover, replaced the o-ring, and checked the impeller for play.


The overflow water is warm/hot to the touch but not scalding. It is not boiling out of the radiator. I've tried two different radiator caps, a Mylers high pressure and the stock cap.

Edited by 2strokeYardSale, April 22, 2016 - 07:59 AM.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • stevethe

Posted April 22, 2016 - 08:09 AM


Make sure you have 50/50 coolant in there. It must be coming from the radiator to the overflow tank. If it's too full it will come out and level off.

  • toten

Posted April 22, 2016 - 11:10 AM


Mine's an 03 but I filled my radiators all the way, my expansion tank maybe halfway, and I don't seem to be losing any. 


When you let yours cool back down, are the radiators still full?


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.