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DRZ400-SM engine coolant overflow reservoir

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I have a 2005 DRZ400SM with 10,290 miles that I got in the fall. I've put about 1k miles on it. As the weather got hotter i noticed for the first time the overheat light came on my bike. I recently drained the engine coolant and put fresh coolant in the radiator following what I researched other people do from this forum. Since then I haven't had the overheat light come on and everything seems to be running fine. But I have noticed that the overflow reservoir is almost full. Does this mean that I just refilled the radiator with an excess amount of fluid or is there potentially an issue with fluid returning back into the radiators after the bike cools back down? The overflow reservoir stays almost always full with only about a 1/2" of space until the top of it. Should I be concerned that fluid isn't flowing back into the bike or is this fine? Thx!

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You may have over filled it a bit,   mine is always about 1/2-1 full,  and when im done riding on a hot day its like 2-3 inches but then goes back down as the bike cools down. 

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seems like the consensus is very little in the tank, I know when I fill the rads that I allow at least a half inch of overflow into the tank

 

your rad cap may be going bad, it is not actually solid on top but underneath that sticker is the pressure relief valve (more or less)

 

you may be purging coolant but it is not returning

 

I completely serviced the coolant system at about 15K miles, flushed the rads, new thermostat, new cap, water wetter treatment, new Samson hoses, I did have to replace the round temp sensor on top of the left rad as it was keeping my fan from NOT turning on when hot

 

I also have Eddy's fan over ride switch I got from Wheeling Cycles

 

Pro-Cycle out of Oregon has a new cap for like $15 or so, I think OEM is like $30

 

living in Texas with the summer heat usually above 100 degrees I stay on top of the coolant situation

 

I don't recall anyone ever saying their coolant tank was ever that full, somebody will chime in here with more info

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The coolant bottle is meant to be run dry or a dribble in it (that's it). and only when the bike is running should coolant expand into the bottle half full at the very most, then that excess should be sucked back into the bike as it cools down. If that's not happening, then I say that you have a pressurization issue.

The s model with fan and stuff, and I live in Southern Texas, ive never seen a over heat lamp on the drz come on.

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When you buy a drz off the showroom floor it dosent have a drop of coolant in the overflow tank. Mine has only seen a 100 mls or so when the bike gets hot. It sucks the coolant out of the tank when it cools down.i would drain the overflow tank and check the coolant level in the rad.if low top it up and go for a ride and see if it pumps coolant into the overflow tank.if it fills it up then you have a problem. Could be a bad cap or head gasket( if it's the head gasket you will see bubbles coming into the overflow tank as well)

Edited by mickeydee
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