06 YZ450F cooling system issue

8 replies to this topic
  • sacfelix

Posted November 01, 2009 - 08:10 PM


I have an 06 YZ450 that likes to build pressure in the radiators while sitting in the garage. The bike has not been started in a week. This morning I went out to the garage and I heard a hissing sound coming from my bike. As I looked around to see where it was coming from I noticed it was the hose that goes from the water pump to the left radiator making the sound while squirting coolant out like it was over heating. I scratched my head and was saying "What the hell"! I then loosened the radiator cap and a large amount of pressure was released. I then proceeded to check all my hoses and made sure they were tight. I just went out side to grab a beer and the damn thing was doing it again.:smirk:
I loosened the radiator cap again and there was twice the pressure than before. My bike has never overheated while riding until last week so I replaced the coolant. I have replaced the coolant several times before and never any thing like this has happened. Any ideas what it might be?

  • locomike

Posted November 02, 2009 - 05:58 AM


A leaking head gasket is the most common cause for pressurizing the cooling system. You can get a "sniffer" test to check for engine gasses in the coolant to be sure.

  • grayracer513

Posted November 02, 2009 - 06:45 AM


I have an 06 YZ450 that likes to build pressure in the radiators while sitting in the garage. The bike has not been started in a week. This morning I went out to the garage and I heard a hissing sound coming from my bike.

You're saying this is all with the engine not running?

  • sacfelix

Posted November 02, 2009 - 06:53 AM


Correct. The bike was sitting in the garage and built pressure in the system. I can understand that the temps have been changing but is that enough to make that much pressure?

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  • grayracer513

Posted November 02, 2009 - 07:03 AM


I wouldn't think so. Strikes me as rather odd. If you haven't changed you coolant in a while, maybe you should. Test the cap, too, to see if it's releasing under lighter than specified pressure.

  • JJRace

Posted November 02, 2009 - 07:41 AM


make sure someone is not messing with the bike. LIke putting alkaseltzer in the radiators or something.

  • sacfelix

Posted November 02, 2009 - 01:39 PM


I gonna change the coolant again and see if it was maybe the coolant because I switched from water wetter to another brand of coolant. Lets see what happens.

  • sacfelix

Posted November 04, 2009 - 02:34 PM


I ended up pulling off the water pump cover and noticed the water pump had excessive play in the bearing so I replaced it and the two seals. I filled it back up, changed the oil and there was a slight wining sound that I thought was normal but now is gone. Anyways, I dont know if that could of caused the pressure build up but at least I found out about the bearing.

  • usp4u

Posted November 05, 2009 - 07:25 AM


almost sounds like some sort of chemical reaction going on. perhaps from the two different coolants? maybe check the make up of the coolants and see if they are both ethylene glycol (or whatever the two types are, I dont remember). never heard of pressurization from mixing two different coolants though.
you said the bike had not been run...has it been sitting TOTALLY static. noone has been kicking it? the reason I ask, is it possible it has a bad head gasket, somone kicked it recently(like that day) could it be sitting on the compression stroke and leaking down through the head gasket ? just throwing ideas out there.

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