OK I know this isn't much to go on but hopefully just off the tops of peoples heads I can get a rough idea where to start. My '94 XJ (4.0L auto) has started to leak coolant but it won't start leaking until it gets fairly warm. Like 4 minutes of idle. The leak looks like it's coming out from behind the crankshaft pulley but obviously it could be coming from higher up and just running down. I don't see any leaks from up above looking down. It's not gushing out but is a steady small trickle. The pulley for the water pump doesn't feel like it has any play in it but the belt is pretty tight.

 

Sounds like the water pump is leaking. Many have a weep hole that starts leaking before it goes.

 

+1 Shaft may not have play because the bearings are still tight. There is a seal to keep coolant from reaching the bearings. Yours could be bad.

 

Also check thermostat housing, upper radiator and heater hose.

 

Ok after crawling under my Jeep and cleaning everything down then removing the fan shroud and electric fan and using a bright LED work light and a mirror I finally could see the trickle of coolant was coming out from behind the water pump as I had hoped. It still sucks but it beats a block leak. But since I just replaced it a couple of years ago with a cheapie one from the auto parts store I may upgrade.

Thanks to all who replied. I figured it was the water pump but just wanted to hear some others say it so I could sleep better.

 

Glad you figured it out. In the future a quick pressure test will tell you.quickly where the leak is. You can "rent" them at autozone if you don’t have one.

 

To quote Howard Hughes, ""No, I don't think I will." I have pretty bad social anxiety disorders so hate doing that kind of stuff. Anyway here's a photo of my new water pump installed. Also did the thermostat while I was in there.