Overheating

BlackJKU08

BlackJKU08

New member
I recently developed an overheating problem and need some direction for what to repair. When I popped the hood, steam is coming from the upper radiator hose at the radiator side. Fan does seem to be running, as I can hear it...trying to figure out the best way to diagnose the issue. Found lots of resources to help with part replacement but not sure where to start.

Thanks in advance, I did try to search but couldn't find what I needed.


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Check to see whether your radiator fins are clogged with mud or debris. A few years ago I had overheating issues and burned up two radiator fans (from constant use) before I discovered that my radiator fins were all clogged up. Hosed out a bunch of mud and dirt and have had no problems since.
 
As mentioned it's not a bad idea to make sure you don't have mud caked in the radiator fins.

From there I would change the thermostat and flush the system. I'm not sure if you're leaking coolant but you should check the condition of your hoses. Pay attention to the fluid that you are draining before flushing, if it's chunky or milky then there a bigger problem such as oil from a possible headgasket issue or someone topped off the radiator with the incorrect coolant.

This is an important read regarding coolant. https://wayalife.com/showthread.php...eep-JK-Wrangler-Coolants-and-Save-Your-Engine!

I'm sure others with deeper knowledge JK cooling will chime in.
 
If it overheats at idle or in town stop and go traffic, it's an airflow problem. If on the highway, it could be a thermostat. Has it actually overheated to where it started running rough or engine making noises? Also, cheap insurance is to replace the radiator cap. Another thing, a 25 dollar laser thermometer is a great diagnostic tool.
 
WJCO said:
If it overheats at idle or in town stop and go traffic, it's an airflow problem. If on the highway, it could be a thermostat. Has it actually overheated to where it started running rough or engine making noises? Also, cheap insurance is to replace the radiator cap. Another thing, a 25 dollar laser thermometer is a great diagnostic tool.
Click to expand...
This ^^. It could also be your temperature sensor. I had one go faulty in my focus, so I replaced it but apparently the one from Napa didn't work either and my motor locked up on the highway without telling me I was overheating. So much for a reliable DD. If your sensor is out then your fan will only kick on at high power when it's pretty much too late. I'd check to see if your fan is running at low speed too, if not it's probably the sensor.

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WJCO said:
If it overheats at idle or in town stop and go traffic, it's an airflow problem. If on the highway, it could be a thermostat. Has it actually overheated to where it started running rough or engine making noises? Also, cheap insurance is to replace the radiator cap. Another thing, a 25 dollar laser thermometer is a great diagnostic tool.
Click to expand...

No, I have made sure to stop as quickly as possible to avoid anything rough or any noises. I'm going to check the radiator today and see what that does.


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Check thermostat housing. They are thermoplastic and known to crack. If it develops a pinhole or crack it will obviously leak but also not allow the system to
build pressure & operate properly.

Edit: MAKE SURE YOU USE THE CORRECT COOLANT WHEN YOU ADD TO YOUR SYSTEM! Sorry for the caps but if you mix coolants you'll have an even bigger issue to deal with!

https://wayalife.com/showthread.php...eep-JK-Wrangler-Coolants-and-Save-Your-Engine!
 
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I just recently had a similar problem. I had a leak and couldn't find it. I thought it was the radiator. When the shop checked it the cap wasn't holding more then 14 pounds of pressure. Like WJCO said replace the cap it is cheap insurance.


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fiend said:
Check to see whether your radiator fins are clogged with mud or debris. A few years ago I had overheating issues and burned up two radiator fans (from constant use) before I discovered that my radiator fins were all clogged up. Hosed out a bunch of mud and dirt and have had no problems since.
Click to expand...

Hosed it out, still running hot...fan turns on but then didn't shut off. I am going to buy a cap, see what that does. I want to try and figure out the issue before doing the coolant touch and change but might have to just bite the bullet.


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Ddays said:
Check thermostat housing. They are thermoplastic and known to crack. If it develops a pinhole or crack it will obviously leak but also not allow the system to
build pressure & operate properly.

Edit: MAKE SURE YOU USE THE CORRECT COOLANT WHEN YOU ADD TO YOUR SYSTEM! Sorry for the caps but if you mix coolants you'll have an even bigger issue to deal with!

https://wayalife.com/showthread.php...eep-JK-Wrangler-Coolants-and-Save-Your-Engine!
Click to expand...

I didn't see any when looking, but if cap change doesn't work I'm thinking I might change thermostat and housing


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As an aside to this topic, is there a best practice for flushing the cooling system? I've got to do mine and haven't seen any write-ups on it (3.8L if it makes a difference).

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Right now it is even getting hot when running at idle for an extended period. I think I need to do a fluid exchange, the inside of cap had some "gummy" residue.


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No recent work done, I will take a pic of it tomorrow, raining like hell outside now, it's like a brown, toothpaste almost, sorry never been great at descriptions lol...Thank you for all the advice.


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If you have an iron block, the brown stuff is not abnormal. It definitely should he flushed, but it sounds more like a flow issue. The worst cooling problem I've ever had to hunt was a water pump impeller that was spinning on the pump shaft. Everything seemed fine but the Jeep (4.0) would overheat at an idle and run a little hot while driving. May be worth looking into.

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