I have filled up the rad a couple times now and after a day of off roading it drops by half an inch below where it started.

I suspect it's leaking out of the water pump but is there a way to tell for sure? I have looked all around and don't see any water. I seem to recall it comes out the bottom of the pump when it does go bad and evaps from there. Just want to make sure before changing out the pump. BTW, no water in the oil and none in the cab to indicate it's leaking there.

 

A bad head gasket or head will not always put water in the oil. Before you spend money & effort on a water pump, check for exhaust gasses in the coolant.

 

There’s actually a tool that you might be able to rent from an autozone or something like that, it connects to the top of your radiator and you build pressure with a little pump, that pressure forces the water out, which helps you find the leak, you’ll find it squirting out. I had a coolant leak, thought it was the water pump, it actually turned out to be the timing cover, it’s a really common issue on the 5.2s. If you do the water pump, I suggest doing the timing cover. I replaced my water pump and then I still had a coolant leak, so that’s when I found out it was the timing cover, so had to take the water pump out for a second time.

 

Not on a 4.0. Timing cover not involved.

Newer water pumps have a "weep chamber" that holds about a teaspoon of leakage from the shaft bearing and allows it to evaporate without showing a leak. When the leak gets bad enough, this leaks into the back of the pulley and gets thrown off on startup. I found this out once when starting the engine while on a lift to bleed the brakes. It gushed out, then quit leaking.

 

Ah yes, just noticed he has the 4.0 🤷‍♂️

 

Thanks Dave. What do think if I was to pressurize the system using the autozone tool as suggested and maybe the water would leak out and then I could start it up and check for water leakage?

 

Tested the system using pressure tester and it appears to be holding pressure. After letting it sit for 30 minutes with pressure I checked everywhere I could to see if there's a leak and didn't find anything.

 

Test for exhaust gasses in the coolant.