If it's boiling over the coolant reservoir, you might want to put a combustion leak tester on it to test for the presence of exhaust gas in the coolant.

 

After doing some more research on my issue I am suspecting a blown head gasket like said. But I wanted to be sure and was hoping someone can answer this for me.

I can drive it all day long and it will operate at 205-210. No coolant loss, no white smoke but when I take it off road and start putting a load on everything it will gradually get up to 220 and then in a matter of 1 second shoot up to 245(I don't understand why it would shoot up like that)and basically overheat. I pop the hood and the coolant is overflowing in the reservoir And if I drive it all day long with no problem/signs how can I have a bad head gasket?? If I went to sell it you will a buyer would never be able to tell it has an issue on road.

 

what's it doing if you leave it sitting at idle for 5 or 10 minutes? sounds like the clutch fan is bad, but there might be more to it. You could have a bad radiator, partial clog or gunk built up inside the head/engine passages, or the water pump is not keeping up. The way it is boiling over makes it seem like the water pump is not working and everything just boils out like if you lost the belt. Unfortunately being that you purchased it used, there is no telling what abuse the PO did to it or if they put stop leak in the radiator...maybe someone else has some ideas

I would put the thermostat back in, let it idle and check your temperature with a scanner/scanner app--don't use the dash gauge.

also what is the status of the transmission? it is using the radiator for cooling, so if your trans fluid is burnt that's not going to help.

 

I've had it idle for 30 minutes warms up then sits at 600 the entire time. I do think the water passages are pretty gunked up because the thermostat hole in the block is pretty dirty.

 

Update on this thread:

I left the jeep sitting for a week and went to do a coolant flush and the coolant that was new a week prior was completely brown i will post a pic. I ran the water hose through the thermostat hole and a bunch of gunk came out. I did about 4-5 flushes (letting it run with radiator flush chemical) and every time I drained coolant it was completely brown never cleared up(not sure if oil or corrosion). I did a combustion leak tester and it was blue the entire time sitting at 210* then I tried putting a load by giving it some gas in drive with the brake held down and it immediately turned yellow and popped the leak tester off the radiator and coolant shot out.

- this is a mud jeep and is not even registered
-I probably have a cracked head and was wondering what cylinder head I should opt for


-just came out (thinking burnt oil)



Sitting for a couple hours

 

if you are going to replace the head the best deal is the clearwater cylinder head for $450 shipped to your door. You will need a new gasket set. They are around $100 - $125. I got mine from Rock auto. When you order the head make sure you get the 0331 cast

http://www.cylinder-heads.com/cylind...ms-fits-87-06/