I have a 1992 Jeep Laredo 4.0L. I have re milled the top end, put in numerous thermostats.. changed 2 hoses on radiator, replaced water pump, and have 2 fans that work by toggle switch. My jeep is still over heating. why????

That leaves the radiator it's self, could have clogged passages...unless you're ahead of me on that and didn't mention it. With bottom hose off, water should flow freely through with a garden hose running in cap opening. If not and water backs up, there you are

Yep that too...good call t'shoes

Hi. Try running the entire with no thermostat and see if it still heats up. Then use a touchless digital temperature reader and check the temperature around each spark plug, down the cylinder wall block, better hose ends, intake manifold and then along the rad. You could be running a very rich and and fuel mixture, or have a blockage somewhere along the rad fluid passages. Its common for garbage to block water passages in the block or rad, causing this overheating. It you're still running hot with no thermostat then you've got a blockage somewhere and a manual rad or block flush should fix it. Allah's start with the simple and cheap stuff first that you can do yourself. Good luck.

Thanks for the help! Going to try a whole system flush... been running w/o thermostat, fans are correct... only i havent done which should of been my first thing to do was a system flush... but when bottom hose is taken off radiator it comes out fine... so didnt think it was that but from all the answers it looks like the only other option for now it to flush the whole system.

I've owned three jeeps with the same engine. They all run hot. The radiator isn't big enough for the engine. Poor design. Change the radiator. It will last a couple of years and then you will have to do it again.

I would also recheck the intake and head gaskets. They are not all punched the same that can cause overheating issues also. A machine powered block flush might help. You can also physically remove the rad to flush and check it. If it's a common problem then maybe a custom rad and lower temp or high flow thermostat might help. Good luck.

Check the upper radiator hose to see if its clapsing. The water pump I purchased at autozone spun the opposite direction of the pump that i removed from my Jeep. You might have the same issue.

Wait, Sean. If the pump did turn the opposite direction.. I believe you. You were there, I was not, so I have no way to dispute your statement. But the belt only goes on one way, it's impossible to make the water pump turn the opposite direction. I am missing something here. Very curious.......

Fordnut in 2000 or 2001 Jeep added a reverse rotation water pump to the mix. The reverse spin oem pumps are stamped with a very small R. It is the exact same pump but the impeller pumps water the opposite direction. I'm guessing jeep modified the belt(s) direction at the water pump in later years. Any year 4.0 water pump can bolt on to any year jeep. So a person buys a reman pump and it fits they have no leaks but the jeep now overheats. Complicating things even more I understand the r pump are not year spacific but dependent on what belt ran accessories you have. Air power steering and what not. -sent from android.

Thanks Sean. This is a new one on me.

I have the exact issue with my 99 tj 4.0 ,no water flow in rad at all ,will overheat & blow cap ,new thick cor rad ,electric fan ,three thermostat. it has a serpentine belt .the back of the belt runs the water pump pulley counter clockwise ,& fan .the impeller on pump i bought new at car quest spins the fins to left backwards ,splash ING the water, not cuping it in like the buckets of the impeller .if it turned to right it would .but I have heard ,that it's supposed to splash the water, but that sounds weird .. all the pumps at the auto parts & on line have only the clockwise one spinning to right & cuping the water .I know the make one ,seen it on ytube reverse water pumps ,it shows the exact pump I need & explain the difference of the pumps .so iam trying to find part # I am pretty sure it is a atech pump ..has any one ever ran across this problem ,all help is appreciated tnks Ric