Temp going up when going over 60 mph in highway for long time

Danihound · Dec 13, 2024

Hello.

My jeep kj 2005 3.7, temp gauge goes a little beyond the middle if I drive at more than 60 mph for long periods of time specially on the highway, but if I stay below 60 mph it stays cool.

Could it be the water pump? Or the thermostat ? Thanks.

KJowner · Dec 13, 2024

Blocked radiator or jammed thermostat I'd guess.
Has it got plenty of coolant in the header tank and is it the correct stuff? HOAT is the original fill and it can react with normal coolant and turn to jelly if mixed.

Danihound · Dec 13, 2024

KJowner said:
Blocked radiator or jammed thermostat I'd guess.
Has it got plenty of coolant in the header tank and is it the correct stuff? HOAT is the original fill and it can react with normal coolant and turn to jelly if mixed.

Radiator is new, so I’ll replace the thermostat first

Jeremy-WI · Dec 13, 2024

Does the fan turn the right direction?

Danihound · Dec 13, 2024

Jeremy-WI said:
Does the fan turn the right direction?

Please explain which one is the right direction ?

REDACTED · Dec 13, 2024

The cylinders on the 3.7 are notorious for running hot. Along with the thermostat, is recommend pulling the plug on the radiator which will drain out about a gallon. Then top it off with concentrate instead of 50/50

Jeremy-WI · Dec 14, 2024

Danihound said:
Please explain which one is the right direction ?

The fan should pull air throught the radiator. If you stand in front of the radiator when the fan is going you shouldn't feel air getting pushed through

LibertyTC · Dec 14, 2024

Is the electric fan running at high speed? Fan should be noticeably noisy if its really warm outside. What are the outside air temps where you live?
Here is the correct thermostat part#..

KJowner · Dec 14, 2024

Driving at 60+ the fan shouldn't be doing anything, the blast of air coming through the front grill should be doing all the cooling the engine needs, the fan does its thing at low speeds.

Jeremy-WI · Dec 14, 2024

KJowner said:
Driving at 60+ the fan shouldn't be doing anything, the blast of air coming through the front grill should be doing all the cooling the engine needs, the fan does its thing at low speeds.

Unless someone repaired the electric fan and switched the wires around. Then it fights the air at highway speed but gets the job done at 25mph

KJowner · Dec 14, 2024

Jeremy-WI said:
Unless someone repaired the electric fan and switched the wires around. Then it fights the air at highway speed but gets the job done at 25mph

That's a possibility, no telling what's been done to a 20 year old car.

Danihound · Dec 15, 2024

Well it has a mechanical fan, it does not have electric fans tho.

uss2defiant · Dec 15, 2024

You are missing the electric fan then.
I believe the non-tow package Liberty only has the e-fan and tow package ones will include a mechanical clutch fan.

Danihound · Monday at 4:19 AM

uss2defiant said:
You are missing the electric fan then.
I believe the non-tow package Liberty only has the e-fan and tow package ones will include a mechanical clutch fan.

should I buy the electric fans ?

u2slow · Monday at 10:03 AM

Our 2005 only has electric. Factory. 3.7L/6spd.

budget76 · Monday at 10:55 AM

do not buy before you know bad and not working. do not throw parts at it. could be clogged radiator. what happens if you throw heater on full force? I had a car where thermostat was in BACKWARDS by toyota shop. was fine at low torque but highway overheat. check thermostat direction. check fan working if one and direction but i doubt backwards.

CheddarGau · Monday at 11:23 AM

You have been given a lot of good ideas here. Have you notice the coolant boiling over when transitioning from highway, then coming to a stop light for example? Once you verify fan(s) and fan clutch are all functioning, including rad (which is said to be new), thermostat and water pump are good, you may want a shop to check for a head gasket issue. Fairly common ish on these older engines. Not the end of the world to repair as well.

Danihound · Monday at 11:47 AM

I’m going to check the thermostat and water pump first , I’ll update on what I found

Danihound · Monday at 11:50 AM

budget76 said:
do not buy before you know bad and not working. do not throw parts at it. could be clogged radiator. what happens if you throw heater on full force? I had a car where thermostat was in BACKWARDS by toyota shop. was fine at low torque but highway overheat. check thermostat direction. check fan working if one and direction but i doubt backwards.

Coolant stay good all the time, I did change the reservoir cap cause it was making bubbles like it was about to boil but the temp stayed at the middle and after the cap change it worked all good.

The only time the temp goes up is when driving at 60 mph or more for too much time (20-30 mins) and then goes down back to the middle if you slow down and stay at 50 mph

RetAF · Monday at 11:51 AM

Also make sure your radiator cap is holding pressure.

Temp going up when going over 60 mph in highway for long time

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