jeepdewd

Im assuming i have a 210 (ome) thermo in my 97 grand cherokee 4L 4x4.

Can i switch to a thermo that is a 180 or possibly cooler?

Will this help combat overheating while the a/c is on?

My rad is completely full and here in the georgia heat sitting at a redlight or drive thru will make the heat gauge start to rise.
A guy on here keeps telling me to get some new fans, mainly from a ford focus and cut them so it fits. Apparently this is a great fix but i want to try some other things before i get into that like possibly putting in a new water pump.

Any suggestions would be helpful

Thanks

KaMoore

Have you measured the temp at the thermostat housing with an infrared thermometer?

jeepdewd

i sure have not. What would this do?

KaMoore

First it would tell you if the engine is running hot. A 4.0l runs between 210 & 225 at normal operating temps.

jeepdewd

what would be the cons of a cooler thermo going in, like a 180?

SatiricalHen

the jeep is supposed to run at 210-225. The thermostat from the factory is 195. If your system is properly maintained and all parts fiction correctly there should be no problems. Running a cooler thermostat won't solve the problem so it's a waste of money.

KaMoore

It will also fail emissions tests in some states.

dave1123

Your operating temp must be at least 195*F for the emission systems to work correctly. If the temp is less than that, you are libel to get error messages and CEL codes. A 195* stat will make the engine run in the 195-210 range and if everything is right, should stay within those limits. I'm telling you right now, a clutch fan doesn't work very well sitting in traffic on a hot day. An extra electric booster fan helps a lot. My 2000 WJ only has an electric fan but it runs low at anything above 195 and high around 210. It doesn't run at all until 195 is reached but then stays running until you shut the engine off. The best thing to do with a clutch fan is slip the trans into neutral and rev up the engine slightly or turn the heater on, yuck! There are several good write-ups here on the forum about adding an electric fan, the one I like is by Bustedback.

A high displacement water pump isn't going to do much but increase the flow rate and that lessens the time for the coolant to transfer it's heat to the air going thru the radiator. You need more air! Also remember the A/C condenser heats the air coming thru the radiator as well.

jeepdewd

I need more air?
Im assuming coming through the radiator then?

If thats the case could i cut some hood scoops or vents in to allow better air flow to reduce the overall heat in the engine compartment?

dave1123

That may help, but more air velocity thru the radiator at low speed works better and an electric fan is the best way to do that. At highway speeds, you don't even need a fan at all, but stopped or at low speeds, there isn't enough airflow to cool it. With an electric fan, you have constant velocity thru the radiator regardless of vehicle speed. Where this is especially true is rock crawling, where the engine it making lots of torque and you're barely moving, AND the transmission is generating heat as well.

A thermostat is used to bring the engine up to a preset temperature quickly and not allow it to run cooler that it's preset temp by opening and closing to hold that temp. The water pump circulates the coolant to prevent hot spots from forming in the water jacket. The radiator's job is to transfer excess heat to the air. The fan's job is to move air thru the radiator. That's the whole story. BUT if you put a trans cooler and A/C condenser in front of the radiator, the air is ALREADY HEATED before it goes thru the engine radiator. Add the fact of 90+* outside air temp, and things can get out of control.

Venting the engine compartment works, but cutting into the sidewalls of a unit body can weaken it. There is the hood, but that exposes the engine to weather. When I used to drag race, some guys put spacers under the hood hinges to raise the back edge of the hood to vent engine heat. The only problem with that is if anything leaks from the engine, it winds up on your windshield. Of course in racing, that's good to know!

One other thing I just thought of. If you raise the back edge of the hood, your A/C will be sucking in that heated air and reduce the cooling of the cabin.

jeepdewd

Awesome reply man, thanks for the help

andrewmp6

First you need to measured the temp at the thermostat housing with an infrared thermometer like said,It will tell you your true running temp.The reason for this is being the age of the jeep is the gauge or coolant temperature sensor could be reading hotter then they are.How hot does your gauge read when you think its running hot ?

97grand4.0

Do not be tempted just because AZ sells tstats for 180. The proper stat for yours is same as mine, 195. ALSO DO NOT buy a duralast, or anything with a so called bleeder for air, etc. as they run about 15 degrees too COLD. A tstat is rated at the temperature it STARTS to open at. Also *I just went through this myself* to answer your question, the PCM will not go into closed loop, meaning it will not use the data from the 02 sensors to trim the fuel, and you will run rich and use gas and foul your plugs in about 4 months. Your monitors might not be ready when you go for inspection, and you will fail, and you will replace $ensors left and right. all obd2 systems, per the NYS DMV, need to operate at 200F for the catalyst to work in the o2 sensors, if you buy an aftermarket off brand that says 195 it will be running 183 when you hook your scan tool to it. STANT Superstat is what I have and it does what it's supposed to , and runs around 204 to 210.
Also dont over tighten your aluminum tstat housing or it will go TWINK and you will be heading back for another one of those, very easy for the stat to slip out, so remove the fan shroud if you have to cut it out, so you can get a clean shot at it.

97grand4.0

A scan tool helps too because it shows the temp the CTS is reporting.

andrewmp6

Yeah but it could be reading wrong also.From the factory all gauges and speedo can be off 20% and be legal.