Coolant issues.Need help!!

[christoswr]

I have an 03 YZ450 and i have a very serious issue with the coolant.I know that its normal to loose coolant when the bike idles for a while but mine needs a refill after a 20 minute session on a track.There is no leak from the radiators it comes out of the breather hose. I need to fix this asap so any suggestions would be appreciated.

[flintlock28]

The coolant level should be just below the filler neck. I followed the manual, which shows the level at the neck. If you fill it to the top of the neck, it will constantly boil over the excess, and mimic that there is a problem.

[smokin529]

Is this a new problem? If it is an over heating issue, try running Engine Ice radiator coolant. My '04 used to boil over all the time until I switched to it.

[tacoma426]

my 02 yz426 has the same prob..... it has never boiled over untill the past few rides. ...if it idles for more than one min it boils over....what could it be???? is this a problem with high hour bikes?????

[grayracer513]

Start by having your cap tested. You should be able to take only the cap to your local shop and have it done while you wait. It may simply have gotten old.

"Tired" coolant can do this, too, as can a mix that has been diluted with an excess of water.

[tacoma426]

thanks gray ill give that a try:thumbsup:

[christoswr]

Start by having your cap tested. You should be able to take only the cap to your local shop and have it done while you wait. It may simply have gotten old.

"Tired" coolant can do this, too, as can a mix that has been diluted with an excess of water.

I use a bottle of coolant on every track day so i dont think its tired. I'll take my cap for testing and hope for the best.

Thanks

[grayracer513]

If you're using that much, it's starting to sound like a head gasket problem. Check the cap anyway, and look for any external leaks, too.

[christoswr]

If you're using that much, it's starting to sound like a head gasket problem. Check the cap anyway, and look for any external leaks, too.

I checked a while ago for leaks but didnt see anything.I will do that again once i clean my bike and ride it for a while.Wouldnt there be any other symptoms if it was the head gasket?

[christoswr]

I'll try a 1.6 radiator cap and engine ice coolant and see what happens!

[Crf250r121]

try to get a pressure test done on the system.

[grayracer513]

Wouldnt there be any other symptoms if it was the head gasket?

There could be, but sometimes the gasket can get to leaking more coolant into the chamber than it lets compression out. That usually gets worse quickly, though. Your stock 1.1 bar cap should be enough if it will really hold that pressure.

[christoswr]

It may sound stupid but would a 1.6 radiator cap do any damage to the bike?

[grayracer513]

Maybe.

The numbers on the caps are in "bars". The term originally came from abbreviating the word "barometric". 1 bar is a rounded metric unit approximately equal to nominal atmospheric pressure at 70 degrees F at sea level. 1 atmosphere is 14.7 psi, but 1 bar was assigned the nice round metric value of 10 newtons/square centimeter, which is 14.5 psi.

Whatever, the standard cap, then, puts 16 psi on the cooling system. A 1.6 bar cap raises that pressure to just over 23 psi. This increases the likelihood of blowing a hose, gasket, or a radiator seam by that amount.

A higher pressure cap not only holds against more pressure, the higher pressure will raise the boiling point of the coolant.

[christoswr]

I've read the the Honda spec is 1.1 to 1.4 bar.Does anyone know whats for Yamaha's?

[Butta]

I've read the the Honda spec is 1.1 to 1.4 bar.Does anyone know whats for Yamaha's?

Good question.....I had a '98 WR400 that I removed the overflow bottle and replaced the radiator cap with a 1.6 (from a KX500) and never had any problems.....

[LVThumper]

I'll try a 1.6 radiator cap and engine ice coolant and see what happens!

That is the hot ticket for me!! 1.6 and Engine Ice!! My '01 426 still gets hot in the tight stuff with the Rekluse, but the boil over is almost gone. The tight stuff and hills I climb around LV in the summer can take a SERIOUS toll on my bike, but fresh oil every 100 miles, Engine Ice, and the 1.6 have really helped out!!

[christoswr]

I think i will go with the 1.6 cap and engine ice but if anyone knows the Yamaha spec let me know.

[wickoffracing]

theres one of three problems it could be....one: is the radiator cap. you can have it pressure tested to see what the pop off release pressure is....your dealer or shop can test that.....two: is your head gasket. if your head gasket leaks it can leak through the outside down the cylinder, or inside into your piston and eng. oil....you'll know this when you drain your oil and its looks clumpy kinda like yogurt...and three: is your coolant level...try putting it just above your fins inside your radiator. no need to fill it all the way up cause it will leak out of your breather tube when it gets hot and builds pressure. good luck!!!

[grayracer513]

I think i will go with the 1.6 cap and engine ice but if anyone knows the Yamaha spec let me know.

The stock cap is 1.1 bar, same as the Honda. The test pressure for a YZF is 25.6 psi, or 1.76 bar, so a 1.6 cap is OK as far as that goes.