Hi,

While driving home yesterday my car started to overheat. I lifted the hood and noticed that only one fan was running. The one in front of the radiator cap was working. It was about 80 degrees outside, but I was driving at 60 mph. I let it cool down and opened the radiator. I started the car and put some water in. It took a little, but there was some still a lot of fluid in there. The fluid "burped" up which means the water pump is working. That would also mean the thermostat is working too, right? I'm at work now and need to hunt for parts. From what I have read, the fans are only supposed to come on when needed in extreme conditions (stop and go driving, climbing big hills). My question is, would the one fan not working cause the overheating? I don't have a lot of time to get the car fixed so I want to make sure I get all the parts I need ahead of time. I have not been able to jump the fan to the battery yet to test the motor yet. Do you think a non-working fan would be enough to overheat the car in the conditions I was driving in or could it be something less obvious to me?

 

I should also add I ran it with the heat on full blast, which kept the temp from rising as fast, but it still overheated.

 

The fan on the left side (driver's side, not the radiator) is only for the A/C and has nothing to do with cooling the engine. The fan on the right is for the radiator, it should be on if the engine is overly hot. But it isn't necessary at 60 mph on level road.

I suggest put in a new thermostat, sometimes they don't open all the way. Always change the thermostat when there is overheating with no other apparent cause.

Also you can unplug the fan switch on the thermostat housing and jumper the wires in the plug to make the radiator fan run all the time the key is on (if it doesn't, something is wrong). Test drive with the fan running all the time and see if there is overheating.

 

Thank you for your reply. I know that the fan on the passenger side was spinning. After letting the car cool the fan stopped (about 1/2 mark on temp gauge). I drove again and the temp slowly started rising. I got about 6 miles before I had to pull over again and try. I'll replace the thermostat since that seems like an easier fix. I put in a junk yard motor about 3000 miles ago and have had no problems until yesterday. When I refilled the radiator, I did it with the car running and waited for all the air bubbles to disappear before I put the cap on. I replaced all of the hoses, but not the thermostat. Sounds like the fan is working properly. I know the upper radiator hose was hot, but I don't know about the lower one.

 

Here is an update...I replaced the thermostat with a fail safe one from Autozone. Also got a new radiator cap. Refilled the system and let it run for 15 minutes with the heat on and the cap off. It make small splashes out the top. The temp raised to 3/4 way up, but the main fan never came on. I turned the car off and connected the main fan to the battery and it spun. Then I switched the A/C and main fan relays. Restarted the car with A/C on and both motors spun, with the main one turning itself off after about 15 seconds. A minute or so later, it turned on again. The fluid stopped spitting out so I let it cool off and refilled the radiator and overflow. This morning I had a full radiator and the overflow was full. Drove 75 miles so far and the temp is staying in the middle. Hopefully it is fixed!