Loosing coolant.

Hi, am new to this forum, find lots of good info here.

I have a problem with my 03 yz450 that I bought used 3 weeks ago.

The last owner just replaced the piston and gaskets just before I bought it.

I have a problem with the bike loosing coolant nearly everytime I ride. It seems to go out the overflow tube from my radiator. I have tried switching rad cap with a friend that have the same cap and nothing changed. The amout of coolant missing seems to be greater every time I use the bike and refill it.

It has 6 hours on it after rebuild and is ridden at dirtroads, and at trails in the forest.

Can this be a leak headgasket?

Any tips about what to look for?

Stop refilling it!

If it's filled cold to the brim, it will overflow once warm because the coolant expands, once it cools your coolant will be lower than the brim because of what was lost, the next time you ride it, it should no longer overflow because it will expand to fill the rad to the top, but not more.

If you're going to be riding woods and trails, I would suggest you invest in an overflow bottle - the TT store sells them for 20.

If your head gasket is leaking it'll show as white smoke out the pipe - but check the torque values on the head if you think it's a problem.

Thanks for the tip but dont think it over filled, ive lost between 1/4 to 1/2 of the coolant the last times I rode it.

Looked over it today and it start to show more signs of a leak, very hard to start( started on first or second kick a week ago), coolant smell when kicking, small white bubbles in the rad when ideling and opening the throttle a little + alot of white smoke.

The smoke and that it was hard to start started today.

Can it be anything else than the head gasket?

Yes it could, but you should hope it's just the gasket.

The gasket isn't that hard to replace, nor is it expensive. Throw a cam chain in while you have it apart, and check your valve clearance before removing the cams.

I've learned from my 2003 YZ450F that you don't want to let is idle for very long as they get hot fast, & will then cause the bike to start leaking coolant

Thanks for the tip but dont think it over filled, ive lost between 1/4 to 1/2 of the coolant the last times I rode it.

Looked over it today and it start to show more signs of a leak, very hard to start( started on first or second kick a week ago), coolant smell when kicking, small white bubbles in the rad when ideling and opening the throttle a little + alot of white smoke.

The smoke and that it was hard to start started today.

Can it be anything else than the head gasket?

1/4 to 1/2 is too much loss for normal operation..

yes it be but this Head Gasket needs to be checked first...smoke is indicating possible head gasket. Lets hope this is the issue.

Is it leaking at all from the waterpump weep hole also at all?

And I agree with greyracer if the timing chain and Camchain tensioner was not changed, this is the ideal time to do both...and they are cheap to replace

No leak from the waterpump hole.

Going to order a chain and a tensioner.

Ok, we went from:

It seems to go out the overflow tube from my radiator.

to:

ive lost between 1/4 to 1/2 of the coolant the last times I rode it......coolant smell when kicking, small white bubbles in the rad when ideling and opening the throttle a little + alot of white smoke.

Yes, a little more than just overfull - I'd be checking the head gasket too - could it be the prior owner didn't torque it right - might just be loose.......

Hmm. can always try to retorque it while I wait for the gasketkit to arrive.

Hmm. can always try to retorque it while I wait for the gasketkit to arrive.
You have to remove the camshafts to access the left side pair of head bolts. Sure you wouldn't rather just wait for the gasket?
You have to remove the camshafts to access the left side pair of head bolts. Sure you wouldn't rather just wait for the gasket?

Ok, didnt know that, havent opened it yet. Will wait then ..

Warmed up the engine today just to check the oil and it has gotten some coolant in it now.

After replacing the gasket and put the bike together, should I re-torque the head bolts sometime?

It should not be necessary to retorque the head.

i have the same problem not with the smoke or any of that only mine keeps loosing coolant out the overflow also i bought a new cap only he gave me a0.9 i wasnt even thinking so i put my old one bak on as it was fine on my other bike but seems to leak on this its a 2000 yz426 manual says 1.1 cap i have to keep filling it up and stopping to let it cool down to open it up to fil it as nearly always its sitting under or just over the fins i was told could be the impeller if you know other wise please let me know deffinatly dun think its my head gasket i just had the whole engine totally rebuilt only got bout 15-20 hrs on it so far cheers

Nathan,

At, or just under the yops of the tubes is the normal cold coolant level. When you fill it above that point, and the coolant expands with heat. the excess is forced out because there is no room for it. If you were to ride it again without refilling, then let it cool, you should find it still at the same level.

Replaced the gasket and that solved the problem.

One thing I wonder about the brutal torque on the headbolts, wont that destroy the threads in the engine after some years?

What do you mean "brutal"?

They are 32 ft/lbs - that's by no means brutal......necessary for a high compression engine....yes, brutal - no.

You're going with your 400 stuff again. The 450 uses a two step torque process:

> Lube the threads and torque to 22 ft/lb

> Remove the bolts and reapply thread lube, torque to 14 ft/lbs

> Rotate each head bolt 180 degrees farther in 90 degree increments

Still, it's only about the same 30-35 ft/lbs and is hardly "Brutal". The aluminum axle nut on your fork calls for 70 pounds, and the steering crown is 105. 30 ft/lbs isn't really that much taken in scale.

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