High pressure rad cap

5 replies to this topic
  • fowler175

Posted July 17, 2005 - 09:01 PM


I'm new to the YZF's and just bought an 04 450. I noticed that it is losing coolant out the overflow tube. Just wondering if anyone is running an alternate rad cap for this prob., and what you are using?

  • 99wr400

Posted July 17, 2005 - 09:08 PM


try evans coolant, or engine ice.

  • mkporn

Posted July 17, 2005 - 09:23 PM


How much fluid? How often?

You either have a problem with the bike or you are riding to slow.... I have had an new 400,426 or 450 from 98 too 2004 and I have never had a real problem with the bike overheating. I ride every thing from dunes to first gear tight single track....Temps from 20 to 100 degrees and have lost maybe a total of two cups of fluid combined.... I would make sure your cap is in good condition (NAPA or the local parts store can check it for you). Make sure your rad's are not blocked or filled with dirt, make sure you don't have a blown head gasket.......

Should have asked the question first... When is it overheating? What are the conditions? I have seen problems occure due to muddy conditions and the rad's getting blocked with mud...... Is it some thing that just started happening? On going? What type of riding do you do most? :applause:

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  • fowler175

Posted July 18, 2005 - 04:32 AM


The bike will do it regardless of how fast I am going, and the top tank of the rad is dry even after a short ride.

  • fowler175

Posted July 18, 2005 - 04:47 PM


Going through the archives, I read that spewing coolant out the overflow when you rev the engine, means a blown head gasket. This is exactly what mine is doing, although it only does it under load, not when you rev it in neutral. Is it most likely the head gasket?, or is there something else I should check before I order a gasket set?

  • mkporn

Posted July 18, 2005 - 09:33 PM


Good way to check the head gasket is to use a leak down tester.... Poor mans tester is to use the hose off of a compression tester and install a air fitting on it. Thread the hose into the spark plug hole and with the bike in top gear and the piston at top dead center apply air pressur to the cylinder... Pull the rad cap and see if it is bubbling......... You can just topoff the rad and with the cap off start the bike and see if it pushes a crap load of fluid and air out... Could be it is just pushing air out when it is sitting in neutral and due too fluid moving about in motion you are loosing fluid :applause:

Your bike should not be loosing fluid..... Also make sure the cap is sealing up correctly.... :eek: :)

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