My biggest fear would be damage to the head gasket.

 

After looking at your pics again. This would be the perfect time to completely redo your entire cooling system. Change out the rad, water pump, T-stat(195deg.) and housing, hoses and fan clutch. And if you are feeling like pulling you dash you can change out the heater core.

 

Agree.Since the car is new to you and already decent age, it's a good investment and gets a lot of things done. All in all the parts involved are reasonably priced (in the US, not here in Oz) and you will thank yourself later to have this done at this stage.

I bet anyway that half of that ridiculously applied RTV is already gone downstream happily blocking stuff. Use a gasket with a only thin smear of RTV to have a nice clean and good seal. Just make sure you clean ALL that gunk of the mating surfaces on the block and thermostat housing to prevent leaks and having to go at it again.

 

So it is fine to use a pressure washer to flush all that gunk out of the engine? And I was planning on replacing the radiator soon, it is pretty beaten up. The thermo housing is completely clear of gunk though.

 

Has any one mentioned the clutch fan? If your truck is only over heating while idling but good any other time your clutch fan is probably not moving enough air. The clutch is cheap and easy to replace plus they go out fairly often.

 

After seeing the photos you posted I can tell you that it looks just like my sons did and what all had to be done to his.

Like already posted by others and myself do it all right now or it will come back at you in a piece meal fashion. Radiator, thermostat and housing, water pump, fan clutch, belts, upper & lower radiator hoses.

I'm going to install a reman. engine in my 99 XJ and when I do all of this will be done also. In fact yesterday I picked up a custom built alternator 164 amps on the bench and a HD starter he built for me.

I guess that I might as well start with all new items on the engine.