It just keeps leaking, which cap do you guys use!!!!!

9 replies to this topic
  • 426 boy

Posted September 28, 2007 - 10:02 PM


Hay guys, im the (most of the time) PROUD owner of a 2002 YZ426F but im having trouble with my radiator cap?

:confused: Coolant just keeps leaking out of the breather so im guessing the cap is broked. so i got a new one but it is still leaking out the breather:foul:

The numbers on the first cap is 1.1 and then the second cap that i put on (the new one) is 100 am i buying the right cap or not does anyone understand what im saying or do i sound like im brain dead!!!! cheers

  • ZéPovinho

Posted September 28, 2007 - 10:21 PM


does it leaks while riding normaly or while street riding ( going trough trafic, stop signs, red lights). its supposed to do so if the engine runs whith the bike stoped, over heating.
check also on a stand whith the cap off running the engine to see if any bubles come out, it can also be a burned head gasket but is very unlikely to be so

  • 426 boy

Posted September 28, 2007 - 11:51 PM


i ride it in mx

bubbles do come out wen i run it wiv cap off and bubbles also come out breather too wen cap is on!!!

  • PatrickM

Posted September 29, 2007 - 12:21 AM


I had that same problem on my 99 YZ400F. I replaced all of the radiator fluid with Red Line's pink radiator fluid. Red Line's fluid has a higher boiling point so it will not boil over as much. I also repleaced my old radiator cap with a 1.6 PSI Radiator cap from Pit Posse. Most stock Yamaha radiator caps are rated at 1.2 PSI.

After making those two mods, I have not had to re-fill my radiator. its been about 6 months since then.

the radiator cap is 19.95.

Patrick M.

  • 426brandon

Posted September 29, 2007 - 04:48 AM


dont worry about it, keep riding and in a couple of days it wont do it any more, its over filled, and the coolant gets hot, it expands and there is more..

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  • MNellis

Posted September 29, 2007 - 08:31 AM


dont worry about it, keep riding and in a couple of days it wont do it any more, its over filled, and the coolant gets hot, it expands and there is more..

I would be wary of the above advice. You keeping riding it like that and don't worry then you'll be worrying when you run the radiator dry and burn up the motor. Been there done that.

  • 426 boy

Posted September 29, 2007 - 05:44 PM


Its not boiling or any thing like that, the cap is just leaking i think, wen i do just leave it it gets so low that i have to tip the bike over so far to even see coolant through the core!! i saw a 1.1 cap on a yzf 250 are they the same caps on the 450 or is it higher

  • rexbond007

Posted September 29, 2007 - 06:13 PM


it's a 1.1

but i upped mine to a 1.3 just because i had a extra cap, it only increased it from 15 psi to 17psi,

  • Solo

Posted September 29, 2007 - 07:29 PM


Stant #11233 can be found at any auto parts store for around $9. It's the same size & pressure rating as stock without the heafty price tag.

  • sirthumpalot

Posted October 01, 2007 - 04:56 AM


If it's blowing bubbles and you're sure it's not overheating then that can be a sign of a leaking head gasget. Run a leakdown test, or in the least a compression test and see if you can detect a leak.

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