2001 Jeep Cherokee Sport - check engine

If your Jeep is overheating and the coolant reservoir is bubbling, it could indicate that there is an issue with the cooling system. Here are a few possible causes:

1. The radiator cap is faulty: The radiator cap is responsible for maintaining the proper pressure in the cooling system. If it is not functioning properly, it could cause the coolant to boil and create bubbles in the reservoir.
2. The water pump is not working: The water pump circulates the coolant throughout the engine. If it is not working properly, the coolant may not be circulating as it should, which could cause the engine to overheat.
3. The thermostat is stuck: The thermostat is responsible for regulating the flow of coolant into the engine. If it is stuck in the closed position, it could restrict the flow of coolant and cause the engine to overheat.
4. There is a leak in the cooling system: If there is a leak in the cooling system, the coolant level in the reservoir may be low, which could cause the engine to overheat.

It is important to address any issues with the cooling system as soon as possible, as an overheating engine can cause serious damage. You may want to take your Jeep to a mechanic for further diagnosis and repair.

Hi Jonny, While the engine is cold the thermostat will be closed, allowing coolant circulation around the engine block and cylinder head but not through the radiator. Only when the engine has reached normal operating temperature will circulation be noted in the radiator. A good test is to remove the thermostat while the engine is cold , start the engine with the radiator pressure cap removed and observe flow. If as I suspect it is there, refit the thermostat and check the heat gauge. If all remains well there is no problem. If the engine overheats replace another thermostat. If there is no circulation with the thermostat removed, there is a blockage in the cooling galleries of the engine. If chemical flushing does not clear it, it will require disassembly of the engine with careful step by step inspection at every stage. If the cylinder head(s) had been removed I would suggest making sure of the galleries not being blocked by installing the gaskets incorrectly. Regards John

I'm assuming you mean a coolant temp sensor. The sensor tells the computer what the coolant temp is.
Normally when a sensor fails the check engine light comes on to warn the driver. Normally but not always.
One thing that could affect both problems you describe is the idle air control valve. If the valve fails or sticks, the engine can stall or have a high idle speed. The computer controls idle speed by how much air is allowed into the throttle body.
The throttle body could also be very dirty.

Your heater control valve will only cause you problems if it leaks or fails to switch to "off" in AC mode. It will not cause the engine to run hot. (unless it leaks coolant). You did put the hoses back where they belong?
I'd replace the thermostat as they can get stuck partially open. On a 92 I'd also suspect the radiator as having excessive rust plugging part of the core. Most times flushing won't get the rust out unless it's done by a radiator shop. Normal temp should be near 210 (f). Use a 195 thermostat.

city driving does not force air through the radiator like highway driving does. if it has overheated, suspect a blown head gasket caused by expansion of the head when warm rubbing against the gasket and tearing it. could be the water pump, pull a heater hose and start engine. if coolant blasts out, pump is working. caution!! coolant may be hot!!! if it trickles, you have a restriction or a bad pump. stupid question, you have coolant in the radiator, right?

I would recommend flushing the cooling system and replacing the thermostat.....easy to do and only about $14 for a new thermostat.If that does not work then you either have a coolant leak somewhere or a bad heater core. I would also pressure test your cooling system before you flush the system to look for leaks in the system

check the casting on your replacement water pump..4.0l engines require a reverse rotating water pump..may be causing your problem.

we have a 2003 and it did the very same thing . Its called cooling fan relay it costs about 60.00 and is located behind the headlight assembly . not very hard to fix if you know anything about cars .

This means your thermostat is bad. Needs to be replaced. Also do coolant flush.

try a new radiator cap, it might old and not holding pressure