Intermittent overheating on 96 Jeep Grand Cherokee

I'm not really familiar with JEEP mechanics but if you've replaced your water pump and it's still overheating with full water/coolant level, you should check the thermostat; when it fails, it's a common cause or overheating in all kind of cars

I'm attaching some links to Youtube tutorial about replacing thermostat in a Jeep but you can expand your Google search using terms
Youtube replace thermostat JEEP Liverty

https://www.youtube.com/watch?v=Y3NpLdG993U

Jeep 4 0L straight six thermostat replacement

Thermostat Replacement Overheating fix Part 1 Jeep


How To Change the Thermostat in Jeep Wrangler


2002 Jeep Grand Cherokee Thermostat Replacement

Replacing the radiator thermostat in any Jeep Cherokee Jeep liberty Jeep...

Okay, it may be due to overheating, that may be the noise you heard, lets hope. first allow engine to cool, open radiator cap or the resivoir cap, which ever is the fill, remove the bleeder at top hose and fill radiator slowly until coolant comes out bleeder.

note if water pump was replaced due to leaking and engine was overheated at that time then it may be a good idea to replace the thermostat .
after filling is done start engine and allow it to run. watch temperature if temp start to climb past half way shut engine down and let sit for 5min. then restart and check level, in res do not open cap . feel air from fan and see if it is getting hot, this may take up to a half hour but do not drive,

A few questions, does this jeep have an electric fan?
when you heard the knocking was engine temp hot?
If you start jeep cold does engine knock?
Did this jeep get a new thermostat with waterpump job?
did it overheat when pump went bad and why did water pump get replaced?

sorry for all the questions ,just trying to get all the info to help you .

According with the Section 7 Cooling System from de Repair Manual, check this diagram (click image for zoom)...

Fig. 6: Water pump mounting bolt locations

To removal...

1. Disconnect the negative battery cable.
   
2. Open the radiator valve and drain the cooling system.
   
3. Remove the cooling fan and shroud as an assembly.
   
4. Remove the accessory drive belt.
   
5. Remove the water pump pulley from the hub.
   
6. Disconnect the hoses from the water pump.

Keep in mind that Grand Cherokee have two sizes engines 4.0 and 5.2L (this last engine is the mine)...






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Since you have already changed everything that you have, I can not think of anything new that might cause your Jeep to overheat. Are you going by the meter in your vehicle or doing separate temperature measurements? I had a defective temperature gauge that caused me to chase my tail till I did separate measurements.

When running the engine TOUCH the bottom part of the radiator fins, if the temperature is not the same or cold, u got a blocked radiator FiNS, and u need to replace it! Check also ur Radiator fan, note down what temperature it started to work. If the Fan works at high temp, means ur TEMPERATURE SENSOR switch for rad fan is not working or it has a higher temp operating value! Hope that might solve ur temperament! j/k!

radiator fan switch next to theromstat housing.












TIM.

may have to change thermostat also, 220 too hot!! check to see if belt on, shake water pump pulley to check for bad water pump, if wobbles its bad, hope this helps!!!

Clutch Fan are known to fail over time, but I wold not rule out the radiator. The small passages inside the radiator will clog due to age. You did not mention how many miles are on the Jeep or if the Aux fan is kicking on.

check all fuse and relay pertaining to the ignition system, make sure all hose are good and the radiator is good, check that thermostat, make sure the fan are working. for the head gasket, check for oil and water mixture in the dipstick

Have you tested the fan sending unit on the engine? disconnect that and if the fan runs (Key on) that is most likely the problem.