So I wheeled this last weekend in the desert and then in the mud. Johnson Valley and Holy Jim in Southern CA for those who care. After a full Sunday of wheeling the mud and hanging with other 4X4s I ran into a bit of overheating issues, but only after touching pavement.

I was running my engine at idle while I aired up my tires, this takes me about 15 minutes. After I completed and started down the road I noticed the water temp gauge was climbing extremely fast. I rolled less then 2 blocks before the collant started to boil out of the radiator overflow. Luckily, two of my buddies are mechanics and saw me pulled over. Together we waited for the engine to cool down enough to add water. We also speculated as to the cause, but nothing was jumping out at us. After adding about a gallon of water I started down to road again. Not more then 3 more blocks and the collant started to boil out again.

So I had to have the Jeep towed to the dealership. They have looked that my jeep and stated, "You have too much mud in the radiator fins, we have to send it to the detailer to pressure wash the engine and the radiator." I saw the radiator before I sent it to the dealership, there was mud on maybe 15-25% of the fins from a mud splash (front and back). I didn't sumerge the front end of the car. I just plowed through some very liquid mud about a dozen times or so. Also the fan was working great and no sign of water/mud past the air filter.

My response to the dealership's service dept was, "It's a Jeep! This is not my first and I have taken it through mud much worse then this and never had a problem." In fact I used to own a 1988 YJ which I drove to death and have replaced the radiator. Jeep overheating issues are nothing new to me, but I did expect my JK to handle the heat a bit better then my YJ pre-radiator replacement.

Do JKs have some issue with mud and radiators? Of course if mud was covering a majority of the radiator and I never cleared it, I wouldn't expect it to cool properly. That is not the case here.

Has anyone else caked too much gunk on their radiator to cause overheating in a JK?

Why would I not have overheated while inflating my tires or coming back from the mud pits, just on the paved road? I say the jeeping gods only rule over dirt and I had good karma with them since I winched 4 other rigs out of the mud and showed some fellow jeepers (TJs) the "good" mud pit.

Really though, I think it was thermostat stuck closed or I have a faulty water pump, but I want to hear if anyone else has had a similar experience and what was done to allow for constant wheeling in mud. Or is the JK not built for mud? I did talk to another built up JK that was too chicken to hit up the mud, maybe this is why.

The dealer service dept says the washing of the radiator was all that was needed and the test drive shows everything is okey, but I don't want to have this problem sneak up on me while wheeling further from home.

I pick up the my jeep later today. Just in time to put on the JKS control arms I baught myself for Xmas that came yesterday.

Attached you will find a pic of my jeep right before I aired up, about 20 minutes before the overheating. I only idled after the picture was taken and did not kill the engine.

 

The big problem with mud is, it gets in the fins between the radiator and the A/C condenser. Most time it will not wash out without removal of one of those assemblies. It will appear clean from the front and back. You can't see in between unless you take one out.

 

The dealership "washed the engine" and said it didn't overheat, but there was still a large amount of mud in the radiator fins you could see with a flashlight. The overheating returned on my way home. Took it to my car washing spot, waited for things to cool down, and hit the back side of the radiator with a steady steam of water for 10 minutes. A large amount of mud ran out.

Everything checks out.

Thanks ronjenx!

 

Good post!!

 

I have heard of this before. My buddy's TJ did the same thing after he got back on the pavement, one good washing from the front and back with a pressure washer and problem fixed!

 

I thought a pressure washer was not to be used on radiators because of the high possibility of bending fins.

 

You're right. Ask me how I know!

 

you have mud caked in the radiator. happened to me a few times and I couldn't figure it out! take a hose and just run water through the radiator, through the grill. wait till it is clear water coming out the bottom and your good! you also have to be careful with the radiator fan motor going out. but yours seems to be the mud caked in their!