tsosi

Hi. I have an overheating issue with my jeep. It's an inline 6 4.0. I reach 210 and it shoots straight up from there without slowing. When it reaches temperature, the radiator electric cooling fan doesn't switch on. I've jumpered the fan and it works. I've replaced the thermostat and the water pump for good measure. They were overdue, as well as my serpentine belt. I've swapped out the relay with no luck. I'm currently trying to find the fan fuse. It's not in the fuse box below the driver's dash (unless it's the 'blower' fuse?). I'm at a loss. Can anyone tell me where to find a secondary fuse box? Or is the cooling fan fuse isolated (inline fuse or something?)? Any other recommendations and suggestions are welcome as well. PLEASE HELP! I have been working on this for several days and need it up and running for work tomorrow!

freegdr

sensor is on radiator next to fan above bottom hose if your ac works switch it on see if fan comes on this willl tell you if relays good which is drivers fender well by air box

tsosi

I disconnected the sending switch and jumpered the connection and my fan kicked on. So I'm in the process of replacing the switch and believe that will fix the problem. Thank you guys.

tsosi

ok so I've replaced the radiator fan switch and it's still not coming on. I've jumpered the fan itself, it works. I've jumpered the circuit from the fan switch, it works. So the fusable link and the relay and fan work. I've tested it with the meter and it's getting 12 volts. Only other thing I can think of is air pockets. My overflow tank has cracks in it and needs to be replaced. Could this be it? It doesn't make sense to me that the fan still isn't coming on. Please help!

DFlintstone

Replace the expansion bottle, (and don't run with it much more than 1/2 full). The switch comes on at like 218*. Without pressure you may well be boiling before it gets that hot.

je4reyk

If your bottle is cracked you need to replace that before anything else, that bottle is probably the cause of your over heating .

tsosi

so the fan won't come on if my pressure isn't corrected?

DFlintstone

Water of course boils at 212* At sea level, (ambient pressure 14.7 lbs IIRC). Antifreez brings that up, Idk how much. The pressure in your system keeps it from boiling up to much higher temps. With the bottle cracked and leaking, (not holding pressure), you may well boil before it gets to the 220* or so it needs to turn on the fan.

je4reyk

Yes ANY leak in the system is BAD ,no cooling fan can save it from overheating.

tsosi

I replaced the coolant reservoir and the hose below it and filled up the radiator at the upper hose as well as the hose itself. I then closed it up, pinched off the hose beneath the reservoir and dumped coolant in it. I released the hose and turned it on bringing it up to temperature. I did this a second time and guess what? the fan came on! It's running just fine now. It was just running rather dry because of the leaks. Thanks for all the help guys. Anyone else reading this for tips, these are very good tips. Remember to burp the air pockets from your system, preferably from the highest point which would be your upper radiator hose. Thanks again!

DFlintstone

And the crowd cheers! Well done. Be sure to check it often a few times, and leave about 1/2 air in there so it doesn't blow again....too soon!