Overheating issue continued (only when turned off)

[Justanotherjeepguy]

I’ve had a problem with my 2000 Jeep Tj 2.5l overheating when I turn off the ignition.

When I’m idling, revved up to high rpms, on the interstate, or any other situation where it’s turned on, I have zero issues with overheating. It stays right under the middle 210 mark (so maybe around 180-190) when running, with minimal fluctuation.

The moment I turn it off, it begins rising 30-50 degrees over a few minutes.

When I start it back up again before it has had time to cool, it starts up very rough. But if I let it cool, it starts up beautifully.

So far, I’ve replaced the radiator, hoses, cap, thermostat, and flushed the new radiator and refilled with zerex G05.

The coolant level has stayed the same and there doesn’t seem to be any leaks.

I do not believe the radiator is a mopar, but it seems to do the job when it’s running.

I also put a small clamp on the overflow hose because it seemed a little too loose on the radiator side (it even slipped off once while off-roading). There seemed to be a few drops that would trickle down the radiator and steam/smoke when it would overheat, but not since I added the clamp.

What might the problem be? Fan? Pump? Head gasket? Let me know what what I should look at first.

I’ve already taken it to multiple shops for this issue—the last shop put in the new thermostat, which didn’t change anything.

I did have a slight overheating problem before where the AC would cause it to overheat some. This is no longer a problem.

 

[Steel City 06]

How hard are you running it? If you run it really hard (like climbing a mountain at full throttle) and shut it off it will overheat due to residual hot spots in the engine. This is a form of heat soak, likely unrelated to the fuel injector heat soak issue commonly posted on this forum. It will happen to any engine. I've inadvertently done it on other cars.

Any time the engine is run hard, you should do some light throttle cool-down or idling before shutting it off. This goes for any engine (especially turbocharged engines). When I pull into a rest stop, I let it idle for 60 seconds before shutting it off. Longer if I just climbed a mountain. Blasting the heater at the hottest setting and highest fan speed will accelerate the cool-down.

Another issue could be improper gear selection, particularly if you have a manual transmission, or an auto that is significantly under-geared. Higher RPMs are safer for the engine at high throttle in terms of cooling for two reasons: (1), there is less fuel being burned during each piston stroke for the same power demand, resulting in lower cylinder temperatures, and (2), the belt driven water pump is sending coolant through the system at a faster rate, which helps eliminate hot spots. I frequently climb mountains on the freeway at 4000+ RPM.


Actual problems could include inadequate water flow, or air pockets or debris in the coolant restricting flow. I would recommend replacing or at least inspecting the water pump. If it is damaged, the flow won't be high enough to adequately cool the engine, but perhaps enough to prevent it from registering as overheating.

Consider also doing a chemical flush of the coolant system. Just be aware, chemical flushes can uncover problems with the cooling system and force a repair. (But you would have eventually found out anyways, probably at the worst possible time.)


For now, start with the water pump.

 

[Justanotherjeepguy]

How hard are you running it? If you run it really hard (like climbing a mountain at full throttle) and shut it off it will overheat due to residual hot spots in the engine. This is a form of heat soak, likely unrelated to the fuel injector heat soak issue commonly posted on this forum. It will happen to any engine. I've inadvertently done it on other cars.

Any time the engine is run hard, you should do some light throttle cool-down or idling before shutting it off. This goes for any engine (especially turbocharged engines). When I pull into a rest stop, I let it idle for 60 seconds before shutting it off. Longer if I just climbed a mountain. Blasting the heater at the hottest setting and highest fan speed will accelerate the cool-down.

Another issue could be improper gear selection, particularly if you have a manual transmission, or an auto that is significantly under-geared. Higher RPMs are safer for the engine at high throttle in terms of cooling for two reasons: (1), there is less fuel being burned during each piston stroke for the same power demand, resulting in lower cylinder temperatures, and (2), the belt driven water pump is sending coolant through the system at a faster rate, which helps eliminate hot spots. I frequently climb mountains on the freeway at 4000+ RPM.


Actual problems could include inadequate water flow, or air pockets or debris in the coolant restricting flow. I would recommend replacing or at least inspecting the water pump. If it is damaged, the flow won't be high enough to adequately cool the engine, but perhaps enough to prevent it from registering as overheating.

Consider also doing a chemical flush of the coolant system. Just be aware, chemical flushes can uncover problems with the cooling system and force a repair. (But you would have eventually found out anyways, probably at the worst possible time.)


For now, start with the water pump.

Thanks so much! I appreciate the in-depth info.

I’ll definitely look at the water pump first.

I don’t usually run the engine very hard except when going up steep hills. My neighborhood has a strict 5mph speed limit, so it has a couple minutes to cool off at low speeds when I come home, but I wonder if that’s not enough. I’ll see if giving it a minute to idle and cool off will help.

Thanks again!

 

[Steel City 06]

Thanks so much! I appreciate the in-depth info.

I’ll definitely look at the water pump first.

I don’t usually run the engine very hard except when going up steep hills. My neighborhood has a strict 5mph speed limit, so it has a couple minutes to cool off at low speeds when I come home, but I wonder if that’s not enough. I’ll see if giving it a minute to idle and cool off will help.

Thanks again!

Driving at 5-15 mph for several minutes would definitely give it plenty of time to cool off. Idling beyond that will probably help, but may just be a band aid.

Definitely check out that water pump. Also do a search on this forum for the infamous heat soak issue. While that shouldn't cause the coolant temperature to rise, it can cause rough idling issues upon restarting.

 

[clubrob]

I’ve had a problem with my 2000 Jeep Tj 2.5l overheating when I turn off the ignition.

When I’m idling, revved up to high rpms, on the interstate, or any other situation where it’s turned on, I have zero issues with overheating. It stays right under the middle 210 mark (so maybe around 180-190) when running, with minimal fluctuation.

The moment I turn it off, it begins rising 30-50 degrees over a few minutes.

When I start it back up again before it has had time to cool, it starts up very rough. But if I let it cool, it starts up beautifully.

So far, I’ve replaced the radiator, hoses, cap, thermostat, and flushed the new radiator and refilled with zerex G05.

The coolant level has stayed the same and there doesn’t seem to be any leaks.

I do not believe the radiator is a mopar, but it seems to do the job when it’s running.

I also put a small clamp on the overflow hose because it seemed a little too loose on the radiator side (it even slipped off once while off-roading). There seemed to be a few drops that would trickle down the radiator and steam/smoke when it would overheat, but not since I added the clamp.

What might the problem be? Fan? Pump? Head gasket? Let me know what what I should look at first.

I’ve already taken it to multiple shops for this issue—the last shop put in the new thermostat, which didn’t change anything.

I did have a slight overheating problem before where the AC would cause it to overheat some. This is no longer a problem.

Hi Justanotherjeepguy- I just noticed the same issue on my 1997 2.5L today. Coolant temps are perfect at 190 to 200 while running, but the temperature rises by 25+ once shut off. As soon as I start the engine back up and idle, the temperature goes back to a normal operating range.

I only noticed this since I just put in a new Mopar radiator and was logging the temperatures both with Torque and a laser thermometer (so it is really happening). The fact that it cools off immediately once the jeep is started leads me to believe that cooling system components are all working properly.

Any additional ideas? Could this be normal but generally unnoticed? Thanks.

 

[Goatman]

Is the coolant blowing out of the overflow tank? Fluid is designed to move in and out of the tank as heat in the system changes fluid level. Always try and let the engine idle for a minute or so before turning it off to help get excess heat out of the system. Can you confirm the fan clutch is working properly? With a weak fan the system works a lot harder to remove engine heat. Easier than a new water pump (tho that's a good idea too). I've had some vehicles make a lot of noise releasing coolant into the overflow at shut-off with no problem other than the noise, obviously you are beyond that point.

 

[clubrob]

Thanks Goatman. No issues with the cooling system at all, it is working fine while the jeep is running or idle. I have found this "issue" on other car forums (especially for older models) and the consensus seems to be that it is normal as the coolant stops circulating after shutoff and there is no electric fan.

 

[Justanotherjeepguy]

Hi Justanotherjeepguy- I just noticed the same issue on my 1997 2.5L today. Coolant temps are perfect at 190 to 200 while running, but the temperature rises by 25+ once shut off. As soon as I start the engine back up and idle, the temperature goes back to a normal operating range.

I only noticed this since I just put in a new Mopar radiator and was logging the temperatures both with Torque and a laser thermometer (so it is really happening). The fact that it cools off immediately once the jeep is started leads me to believe that cooling system components are all working properly.

Any additional ideas? Could this be normal but generally unnoticed? Thanks.

I never did figure out why It was happening. I replaced the entire cooling system—thermostat, hoses, coolant, radiator, etc. It still happened.

If I had been running it hard for a while and then turned it off
, it would have a really rough startup (for maybe 15-30 seconds) and then it would cool down and act normal. But other than that, it didn’t seem to cause any issues, so I gave up trying.

I actually sold it a couple weeks ago because I found a good deal on a 2006 Rubicon. So I guess it’s up to it’s new owners to figure out.

I hope you can get some advice that will help! Good luck! Maybe it’s just a 2.5L thing?

 

[Sniperallen90]

Happens on my 98 Xj 4.0 I have also replaced everything to do with the cooling system if I have to shut the jeep off but I know I’m gonna start it back up shortly after I pop the hood so the jeep cools down faster but I sure would like to know the fix

 

[Cotnballs2000]

Never mind, didn't see you sold it