My jeep on several occasions has had the coolant overflow out of the reservoir because it is getting too hot I'm guessing. It's pretty much boiled several times and just poured out. The times it happened were all after simple, shorter drives so I'm not pushing it hard. I don't know why its doing this. Maybe i should try a new type of coolant? Go get a coolant flush? I have no idea.

 

? water pump, t stat,cracked head,head gasket,rad plugged.
what kind of car do you have?

 

92 jeep cherokee laredo 4.0 HO

 

I would start radiator cap. While I am not a fan at throwing parts at something to try and fix it they are relatively cheap and quick to do. Same thing happened to me in my '00. Replaced it and been fine since.

 

I recently had a similar experience, in which a 10 minute drive to work would cause my coolant to overflow. I took it to my mechanic and it was diagnosed as a faulty water pump. It was replaced and the problem hasn't happened again. It had to side effect of also eliminating an in-town overheating problem that I had been having since acquiring the Jeep a year prior. At the time, the water pump had 65k miles on it. ymmv