Where Does All the Coolant Go?

Almost every time I ride my 05' cfr450r, I have to put in about two cups (1 pint) of coolant. I just run Peak 50/50 pre-mix because it uses so much. I'm not about to use the much hyped 'Engine Ice" at the price they ask for it. My question is that since my bike does not leak coolant and I never see the radiator cap blow steam, where does all the coolant go? And should I try a high pressure cap? Are those safe? I was thinking that maybe my cap vents slightly and I'm not seeing it. And one last question - When I'm riding and have to wait for somebody, should I immediately kill the bike and never let it idle?

you could put a little bottle on the end of the vent tube and see if it catches anything.

there is always the possibility that it is leaking into the combustion chamber. im pretty sure that was happening to the CR500 i rebuilt a while back.

it doesnt just disappear. if there are no signs of leakage, its not coming out the vent tube, and its not in your oil, its probably coming out of your exhaust.

as far as idling goes, you can let it idle for a minute or two, you dont have to kill it right away if you dont want to.

So it's not normal to use that much?

How much do the rest of you guys lose per ride?

There is no white smoke either and no sign in the oil, so how can it be leaking into the combustion chamber?

My '08 was/is doing that too. I put an overflow bottle on and caught nothing but was still losing about the same amount of coolant as the OP. I think it was actually coming out the weep hole. The thing is, it doesn't come out until it's fully pressurized and then it mostly evaporates so I never noticed it. Also it seems like after a few cups leak out it stops? I just got a Boyesen water pump cover and impeller and when I installed it I noticed the leak from the weep hole. Check me on this but I think that the weep hole leaking can only be caused by the water seal inside the case. I am gonna find out for sure and then order the seals and bearing (while I'm in there) for the water pump shaft.

Good luck,


No it is not normal to loose coolant like that. Possibly leaking out the weep hole on your WP?? It would be hard to notice it since its on the bottom side of the motor and may only leak when you give it throttle.

Either you are burning it, it is leaking out under the cap, going into the oil or coming out the weep hole. My guess, if the oil looks good and the plug looks good, I would change to a high pressure radiator cap.

This same thing happens to my 03. I always have to add what seems like quite a bit of coolant each time.

I've got a catch bottle -- sometimes there's about a spoonful captured in there, but not nearly the amount that I have to add back in. It's not leaking out anyplace else that I've been able to see.


I'm actually pretty sure that it's going through the motor, because I can smell it.


So.....what do I need to do about it? I guess that a seal between the coolant passages and the chamber is bad(?)


Thanks for any help.

Yeah, if you are using standard anti-freeze in your water, you will get a sweet smelling exhaust note if you are leaking into the cylinder.

Where could it be leaking in at?

If it's a seal or something that's not big of a problem. Is cracked cylinder something that's possible? Man I hope not.

either leaking at the water pump , in which case get a new water pump shaft, seals and bearing




your head gasket is leaking.  thus time for a top end job

as many stated, it's hopefully just leaking the water pump weep hole (and search - lots of threads on how-to do the fix). if it's actually getting in the engine, that's another fix. you smell it, but are you sure it's not just getting on the exhaust from the overflow ? it's easy to have a burn hole in the overflow on the crf as it runs really close to the exhaust.

if you are filling it to the tippy-top of your rad, you WILL loose some coolant. It has to expand when it's warm. Don't fill it all the way to the top of the neck. Just fill to barely the top of the fins. Then once it cooled after a ride, put some in and if it doesn't take any to get to the fin tops, you are good..

Edited by MELK-MAN

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