Always replace a water pump with a leak, whether it is the gasket or the pump.
Bars or other "stop leak" products won't cause leaks.
These products are used to get you out of a jam, not to fix a leak permanently, leak will get bigger and will start leaking again.
They should be flushed out as soon as you can find and fix the leak.
They won't "clog up the system", that's a popular myth
BUT(big but),......On older systems the particles in the "stop leak" can clog already narrowed radiator or heater core passages, so shorten their life unless flushed out sooner than later.
Common leak on the 4.0l OHV is intake gasket just above the water pump, passenger side or at the rear drivers side.
That is where coolant passes thru the intake from one head to the other.
You can buy a UV(ultra violet) dye kit with UV flash light for under $25.
You put the dye in the coolant then drive the vehicle till it is warmed up, so dye is mixed.
Then shut down engine and look for leak with flash light.
Works for oil leaks and transmission leaks as well
You can also rent cooling system pressure tester kits, it is a gauge and a hand pump that fits on rad cap opening.
You pump up the system to say 20psi, cold engine, and then see if pressure starts dropping, if it does you do have a leak.
But it is often much easier to find a leak on a cold engine in any case and with 20psi of pressure pushing coolant out the leak point it is easier to find as well, just keep pumping it up as pressure drops
Oil on underside of engine will flow from the leak backwards because of air pushing it when driving, so look under the truck and find where it is dirty then move forward until it is clean, oil leak is there
Last edited by RonD; 05-03-2015 at 03:51 PM.