Okay, check this out. After driving home from work on Saturday, (about 5 miles, mainly highway speeds, temperature in the mid 90's, high humidity), I shut the car off and come inside to change before washing it. When I come back outside, I noticed coolant dripping underneath my car. I opened the hood and couldn't really tell for sure where it was coming from. It looked like it was down around the bottom of the radiator. I went ahead and washed it, detailed under the hood, topped of the radiator and the coolant recovery tank and then it got dark and late so I went in. Due to other committments, I didn't have a chance to do anything with it on Sunday. I drove to work this morning, same distance same speeds, but much cooler, mid 70's, average humidity. When I shut the car off, again coolant is leaking from under the car. Again it looks like it's from around the bottom of the radiator. This evening when leaving work, I check the coolant level, and it's okay to drive home. I drive home, again mid 90 temperatures, average humidity, highway speeds. Shut the car off anticipating a coolant leak, and nothing. I even start it back up and race the engine a while and once the electric fan kicks on, turn it off to see if it's leaking, again nothing. What is going on? Anyone have any ideas?

 

Check the weep hole in the bottom of the water pump. When the pump starts to go out, it'll start dribbling out of that hole and usually it runs down the lower radiator hose onto the radiator support, and drips onto the ground from there.
-Rich-

 

Does the water pump ever do this intermittently, or will it drip every time until it's fixed? The reason I ask is that Monday evening when I drove it home, no leak. This morning when I drove to work, I thought everything was fine. When I parked it and shut it off, no leak. Two hours later I go out and look at my car and there's a pool of coolant on the ground. When I get off work, the pool has turned into a stream and it continues to drip while sitting. All the coolant is out of the radiator, so I fill it up and drop it off at my mechanics shop. Doesn't seem to drip while the engine is running. It seems I remember once before when I had to replace the water pump that it did something similar.

 

Yes, it may only leak when you shut it off. The reason why is that when you shut it off pressure builds in the cooling system--the added pressure forces coolant past the bad seal on the water pump(if the water pump is bad). Turning the radiator cap back one notch will reduce the amount of pressure that is allowed to build before it goes into the overflow--this is useful if you have to get somewhere to put the pump in.