Overheating problem

501 · **Posted:** Sat Jun 28, 2008 3:07 pm

My KJ has been having a overheating problem for the past few months. Some days it will work great, then all of a sudden it wants to over heat for the next few days. Any one have a clue why?

I replaced the radiator cap already (cheapest fix!). Then today I disconnected the fan and hard wired it to see if the fan was working, and it did. I did notice the connector that hooks to the fan leads has a spot that looks like it got hot and burned a little and the wires that supply the power to the fan does get really hot. I was wondering if theres a bad connection there, could that be causing the wires to get hot.

Also, I was talking with a mechanic friend and he thinks it might be that the fan is over working and is about to go out that's why the wires are hot.

I have been following another thread here in the forums that is simular to this ended up with a bad relay, I don't remember him saying that his wires got real hot though.

I'd hate to replace the wrong part and have to buy the other.

Do you think it's :

the Fan?

the relay?

Just the connection to the fan?

All three?

sleeve84028 · **Posted:** Sat Jun 28, 2008 7:01 pm

Replace the relay first. It's the most likely cause of the problem.

Tokyojoe · **Posted:** Sat Jun 28, 2008 8:24 pm

thermostat?

SoDakJeep · **Posted:** Sat Jun 28, 2008 8:29 pm

i voted all three because it seems anytime you think you have a problem fixed it ends up being the other part hahaha. its Murphys law you know haha

tommudd · **Posted:** Sat Jun 28, 2008 10:01 pm

Tokyojoe wrote:

thermostat?

X's two

tjkj2002 · **Posted:** Sat Jun 28, 2008 10:11 pm

501 wrote:

My KJ has been having a overheating problem for the past few months. Some days it will work great, then all of a sudden it wants to over heat for the next few days. Any one have a clue why?

I replaced the radiator cap already (cheapest fix!). Then today I disconnected the fan and hard wired it to see if the fan was working, and it did. I did notice the connector that hooks to the fan leads has a spot that looks like it got hot and burned a little and the wires that supply the power to the fan does get really hot. I was wondering if theres a bad connection there, could that be causing the wires to get hot.

Also, I was talking with a mechanic friend and he thinks it might be that the fan is over working and is about to go out that's why the wires are hot.

I have been following another thread here in the forums that is simular to this ended up with a bad relay, I don't remember him saying that his wires got real hot though.

I'd hate to replace the wrong part and have to buy the other.

Do you think it's :

the Fan?

the relay?

Just the connection to the fan?

All three?

Well this is not going to be cheap in any capicity,if the connector looks like it was burnt,well then that connector(and possible wiring) needs to be replaced since burnt/overloaded wires will overload and heat up real fast and the insulation has been degrated.Then you need to trace the problem for the overload/high heat,look at the fan relay(10" below the battery) and then dis assemble the fan and check the motor brushes.This is where I would start at least.

The t-stat is the least likely cause of your problems,but there is still a chance it may be bad but not likely since it would be more of a constant problem.How many miles on your KJ? What year? It may be time for a coolant flush and new t-stat and hoses anyway,don't believe the 5 year/150,000mile coolant bullsh#t since it's more like 3 years or 75,000miles at most before the HOAT(GO5) coolant is pretty much toast(less for Dexacool or the green stuff).Then you got the possiblity of a bad waterpump but that is just as likely a cause of a intermitant ovewrheating problem as the t-stat.

04jeepkj · **Posted:** Sun Jun 29, 2008 12:44 am

I just had the same problem turns out the fan doesn't like mud too much lol. . . If you have a 2 speed fan the replacement is going to be $465.00 however you can go with a dorman oe soultions fan and get a 1 speed fan and wire it up, i put a switch in the cab for it. much better than stock i think. so far havn't had a problem.

501 · **Posted:** Sun Jun 29, 2008 1:08 am

It's an 03 with around 93,000 on it. I took everything apart today and cleaned thigs up. There wasn't any mud in/on the fan but I cleaned it any way. After putting everything together again the fan ran fine and would kick on and off like it should, but the wires are still very hot. Being a ex-electrician, I was thinking if there's a poor connection to the fan, that could be what's heating up the wires. Arching in the connector could do that. So I guess I'll end up doing all three, changing the relay, then the Fan. When I replace the fan I'll redo the connector to the fan.

Now comes the hard part........... getting the money for the repairs!

Thanks guys!

Tokyojoe · **Posted:** Sun Jun 29, 2008 4:04 pm

Never go to Firestone for troubleshooting and repairs. I went to two of them when I had a Toyota pickup and both stores tried to rip me off. My Yota was overheating and the guy tells me it's my waterpump and proceeds to show me wiggle in the fanblade shaft. Barely noticeable (he was probably giving it everything he's got). I went home and replaced the thermostat only and no problems for another 100k miles (I sold it at that point). The other time was when my brakes were squealing and they said I needed to replace the entire brake system. Everything! I replaced the pads and rotors on my own and no problems.

501 · **Posted:** Tue Jul 01, 2008 10:34 pm

So far I cut the connector to the fan out and replaced it with #12 Sta-con connectors. The fan now comes on and off like it should and the wires are no longer getting hot. I'm going to give this a try for a few days and see if that was my problem.

dgeist · **Posted:** Wed Jul 02, 2008 10:45 am

tommudd wrote:

Tokyojoe wrote:

thermostat?

X's two

X3. Cooling systems don't just spontaneously stop working properly. If you're driving at highway speed without too much load, an engine can get by for a good long while with passive cooling onlye (no fan) If there is a wiring fault, then fix that, but I'm betting the fan is being pushed past its designed duty cycle because of something simple. Start with the basics, like ensuring the cooling surfaces are all clean and that fluid is actually flowing through the block (i.e. thermostat). without good flow, no amount of relays, wiring, and fans will ever help.

tommudd · **Posted:** Wed Jul 02, 2008 12:30 pm

I have seen a lot of T stats work one day overheat the next, they will stick closed at times which will make it run hot, then maybe after its cooled down will open the next time.

If the wires were hot and burnt then most likely thats the problem, but next step for me would be the T-stat if that doesn't fully take care of it!

501 · **Posted:** Wed Jul 02, 2008 6:49 pm

Thanks guys, I'm watching things close. I blew my engine on my Amigo before and it really sucked! So I don't want to do that again.

Overheating problem

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