As some of you have seen, I've been diagnosing a coolant leak under my jeep for a little while now. I think I've made a breakthrough ... well sort of.

I see that the coolant is coming out of the coolant reservoir overflow. It comes out as soon as I shut my engine off. A small puddle of coolant will form on the ground (about two cups or so) before it stops.

Also this only happens when it's really hot outside.

This can't be normal right? What's up with this?

 

Are you over filling the reservoir leaving no room for expansion? How long since the radiator cap has been replaced?

 

The reservoir is filled between the two marks. The radiator cap was replaced about a year ago. Could it of gone bad already?

I had no issues untill it started getting warm outside. It did the same thing last summer.

 

Get it pressure checked.

 

You're saying that when you turn the engine off, the overflow reservoir bottle fills completely and overflows a couple of cups? When it cools does it suck some of the coolant back into the radiator?

Caps are cheap -- I guess I would try another 16# cap as a first step and also make sure the surface where the cap valve seats in the filler neck is not damaged.

 

Yes and Yes Pelican

Also I would like to add that I haven't heard the radiator fan go on full blast for a long time. It's on the slow speed all the time. Could this be alowing the coolant to get to hot?

 

I just realized that my electric cooling fan isn't working. Could this be allowing my coolant to get to hot and thus boiling out of the reservoir?

 

Coolant shouldn't boil until your temp gauge is pegged if the cap is operating properly. What's your temp gauge reading?
But yeah, check the fan clutch and fuse/wiring for the E-fan.

 

The engine isn't overheating yet. But I can hear the coolant boiling when I turn it off. Maybe I should change the radiator cap just to be safe.

 

I would were it mine. Also wouldn't hurt to borrow the pressure tester from one of the local auto parts stores and check that the whole system holds. I assume you have 50/50 or so antifreeze in there?

 

yep I got 50/50 in there. I think I will get it pressure tested if a new radiator cap, and fixed electric fan don't work.

 

Hopefully it isn't your head...if the head gasket has a slight leak, it can allow combustion gases into the cooling system, which would cause enough pressure to blow coolant out of your overflow tank. Happened on my old Ranger.

 

Bubbles in the radiator while it's running would be a dead giveaway. My ranger (4.0) shot coolant out the reservoir like a geyser when the head gasket went.