was under the hood yesterday doing some routine maintenance and noticed that my coolant level in the resevoir was below the min mark? Last week it was at the full mark and have not noticed any leaks!
where did it go?

 

Did you perform both checks when the motor was the same temperature? Or was it hot last week and cold this week?

Evaporation from the system is normal, even though it is a "closed" system. However, a change from max to min in one week (at the same temp) isn't normal.

I'd top it off and keep an eye on it.

 

It sounds silly, but sniff around under the hood when you park it with the motor hot. Evaporating anitfreeze has a strong and distinct odor.

Last year my radiator hose clamps were not tight enough (they are the old fashioned screw type) and I was slowly losing some.

 

Also, check to see if your thermostat is leaking. Just found out mine is ... and I am 3000 miles out of warranty. Should have brought it in 5000 miles ago when I noticed low coolant levels and saw some dripping. :(

 

Maybe it ran away with the oil. Sorry, I couldn't resist with all of the where did my oil go threads hanging around.

 

I had the same thing happen to me recently after a long trip. I haven't noticed anything on the ground, but am trying to keep an eye on it. Let us know what you find out.

 

Just for being courious, I just ran out and checked mine, same issue, changed oil last week and the reserve was at max level, today its at min. level...no dripping leaks.

Topped it of and tightened all the hoses. Will see what happens. Engine temp was the same as last week give or take a few degrees.

 

If there was some air in the cooling system, it will tend to purge out when the enging is at operating temp, and then the system will replace the air with coolant from the over flow as the engine coools.

 

this is my best guess as well....i used to here a "rushing water" noise inside the Jeep as soon as i started the engine. almost like air gurgling through the system. Coincidently when i didn't hear that noise anymore is when i noticed the coolant level drop. Topped it up and it has not moved since. i'll keep an eye on it regularly.

thanks for the feedback guys!

 

I noticed the same thing last summer and found a small seep around the water pump. Not enough to drip but over time the fluid level went down. Dealer replaced under warranty and mentioned that this was a common problem from the factory.