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FAQ Grand Cherokee 4.0 overheating problems
1) Check coolant level. Before doing anything else check to make sure the coolant level in the radiator is at the proper level !!!! ONLY WHEN ENGINE IS COLD !!! just remember to hot to touch to hot to open.IFthe coolant is full check the color it should be (mostly yellow) and not dirty and grimmy. You can get a coolant tester at the local auto parts store and follow the directions coolant will not work if it is bad.
2) Make sure the radiator cap is working properly these are pressurized systems and must mantain a certain psi or the system will not operate correctly , there cheep go ahead and get a new one.
3) Check (visually) the radiator and surronding areas clean any dirt , leaves , anything blocking the radiator fins and make sure the fins arnt damaged bent crushed etc.This will lower the operating conditions of the cooling system.If your jeep is an automatic transmission the transmission cooler and radiator are sandwiched together check for pin hole leaks by spraying soapy water around to c if and steam or pressure is escaping radiator.
4) Check the serpentine belt , mechanical clutch fan, and alternator, water pump, power steering pump etc. These are all connected together by one belt thats routed up and around pulleys and pumps if the belt is making noise or damaged slick looking, cracked , loose ;not only when it breaks you will overheat you will loose stearing etc. If the belt is in fact defective it can cause premature wear on all of the above beearings and so on it will eventually wear your water pump out causing poor circulation. Check the fan by ( when engine is off) turning it u should feel resistance if it spins freely chances are the "fins" or propellers on the pump are rusted away or bent.
5) Water pump and thermostate: The best way i have found to check these are as follows check underneath the water pump housing when it fails most often itbwill weep coolant from a tiny hole , if u have coolant puddles or smell coolant check underneath the pump its under the fan. If you have absolutely no heat after the jeep warms up or it warms up slowly it could be water pump , or thermostat is failed in an open loop. IF the upper radiator hose is not hot after 15 minutes or so ( or when jeep warms up) it could be thermostat or a dieing waterpump.
I may edit this as I am sure I have left some things out. Feel free to email me at [Email removed]
* Most often the water pump will leak or squeal awfully or make sounds like marbles being rubbed together if its dead or dieing but I have had a couple where I had to take off the pump to c and sure enough the impeller s where gone or damaged. If the water pump is faulty and your replacing it yourself do yourself a favor and get good parts, a new thermostat even if its good , new serpentine belt, good gaskets not the cheap ones that come with them and use a good quality gasket sealer AS WELL as the gaskets.