Jeep overheating My 91 jeep Cherokee is overheating I replaced the water pump hoses radiator cap had it flushed .The only thing I have not done is replace the radiator. What else could be wrong?

thermostat in backwards.the part that senses temperature change isn't exposed to the hot coolant inside the engine. , or coolent passages clogged, here is what sometimes will happen:



They can and will totally clog up, try to flush the system if not too far clogged.

Hi David, How long did you run the engine before checking the temperature? The thermostat will only begin to open when the engine has warmed and the gauge begins to move. If after giving it a correct warming period it has still remained cold, I suggest the following. As you have already replaced the water pump, thermostat and radiator cap, the radiator may be blocked. Carry out a back flush, meaning, use a good quality radiator flushing chemical and follow the instructions carefully. Run the engine in accordance with the instructions. Let the engine cool and then draining, flushing the system by connecting a hose pipe with a fairly good head of pressure against the usual direction of flow. If that fails you may need to replace the radiator. Let me know how you get on, Happy new year Regards John

Did you also replace your thermostat? If it's stuck closed, engine will overheat.
When you did the HG, did you have head checked for cracks or warpage? A cracked head will cause severe overheating.A warped head may or may not show signs of external coolant leakage. Either of these conditions can occur if overheating is severe enough.
Are your hoses in good shape? An old hose can collapse when it's hot, and restrict flow. Feel them (when cool) for any sign of sponginess.
New radiator cap? The cap provides a seal to pressurize the cooling system.
Finally, how about your water pump? Any sign at the weep-hole of leaking coolant? Your water pump inner seal is bad, remedy is a new water pump. Or maybe the pumps' fins have corroded and not pushing coolant sufficiently. If there is corrosion, get the whole system flushed and start anew.
Pull your spark plugs and look for any sign of coolant in the cylinders. I know it's a pain to keep going back and checking, but you gotta be thorough. Plugs may be blistered white from overheating, but if you get it fixed, they should be alright.
Now, finally, really: sometimes, Randy, just a small air pocket in coolant can cause overheating. So, make sure you bleed the system if it has a bleed screw, or fill, cap loose, run engine till t-stat opens, level in radiator drops, then re-fill, and add coolant to your overflow reservoir to around the full hot mark. Tighten cap, and you are done. Good luck.

How to diagnose an overheating 3.7
It might be the timing belt!

If the fan is coming on,then the radiator,is bad,or the engine ,has a crack between the valves,in the head.

Sounds like the radiator is clogged, have the cooling system flushed, the water pump pumps water into the engine and it comes out the top hose to return to the radiator to circulate through it to cool, if the radiator is clogged the water pressure will build on the top hose, also look at the bottom radiator hose, if it collapses when you rev the engine the radiator is clogged, although sometimes the bottom hoses are reinforced with wire to prevent them from collapsing so just because they do not collapse it does not mean the radiator is not clogged.

Assuming you dont have a blown head gasket the most likely thing is a clogged radiator. Lee

I think you may need a new radiator core.Flushing can only do so much and if the core is badly blocked no ammount of flushing will solve the problem. You could also chech there is no air in the system by undoing one of the heater hoses on the engine. Make sure there is no problem with the bellts and the water pump is spinning. Also check the water pump for any leaks or wobble on the shaft. If the impeller is bady corroded you can have heating problems.

How long as the radiator cap been on the car? If it is from the factory, replace it with a new cap and see if that helps.

Good Luck

my 91 did the same thing an all i did was pull the thermostat out.it now runs at 210 degrees and i live in phoenix,az.115 degrees outside.