Cooling fan racing in Ford Explorer


Short version: Should I be worried – I’m on an extended road trip – that the cooling (radiator) fan is racing sometimes in my Ford Explorer? Or, more specifically, am I running the risk of serious problems by not having the car checked out until I get home from vacation?

Long version: My family and I are on vacation - we drove from Austin, TX to Denver, CO. The day we arrived here, I noticed that if I stopped and idled for a minute (when the kids stopped for a bathroom break, or at a red light), when I started again my cooling fan was racing - and I mean a jet engine was under my hood. But once I got up to 2nd or 3rd gear, or say 40 mph or so (couldn’t tell if it coincided with a gear change), it went back to normal until I stopped again. No check engine light. Otherwise the car appears to be acting normally.

Keep in mind that the 2nd half of that day we drove up and over Raton Pass and then drove into Denver. So hilly doesn’t quite cover it.

The next day we drove up in the mountains west of Denver, and sure enough it started doing it again.

The next couple of days – when we have been driving around in the city – it really hasn’t done it. Just first thing in the morning – once – each day, and later in the afternoon (say, if we were in a lot of stop and go traffic).

Again, no other odd behavior.

Since this is a 2004 Ford Explorer, I can’t check the transmission fluid - there’s no dipstick. (All the other fluids, including coolant, are fine.) I’m a little worried the transmission is getting too hot. But I suppose it could be a bad thermostat (engine gauge is behaving normally; warms up to mid range and stays there) or maybe a bad transmission temp sensor.

A couple more things I’ve tried: With the engine cold, I wiggled the fan front to back, no movement (so I assume bearings are okay), and I tried rotating it and there was some resistance at first (say, a quarter turn) but then it turned (to me) seeminly freely. After a 10 minute city drive in traffic, it turned freely as well.

One more thing: I’ve noticed the fan racing the first drive of the day before, in Austin, over the last year or two. Only the first time I accelerate. Intermittently (maybe once a month). So I’m less worried about the first-time-in-the morning since that seemed to be normal for this car.

Anyhow, like I said earlier, I’m worried whether or not I can wait to drive back to Austin before I get the car checked out. I don’t really have the money to do it here on vacation…

Or am I just being paranoid and this is normal?

Any ideas?



If this vehicle has an engine-mounted fan, as opposed to electric, radiator-mounted fans, it sounds normal to me.

The fan clutch will lock up and spin the fan faster depending on the temperature of the air coming from the radiator. When the clutch loosens up the fan slows down and makes less noise.

If the engine isn’t overheating I wouldn’t worry about it.

You are putting the motor and specifically the cooling system(s) under a lot of stress, due to the load, hills, and hot weather. If the temp guage isn’t going above normal and you aren’t blowing coolant out of the overflow reserve tank you should be ok. Just make sure every morning before running the truck that their is coolant at the proper level in that reserve tank. If not, top it off with some 50/50 mix before heading out for the day.

You describe the correct operation of the fan under the conditions you indicated.

Thanks all for the reassuring replies. Guess I was just worried, being a thousand miles from home and never had my car act this way before.

Just out of curiosity, what symptoms would I experience if my tranny does start to overheat? And what would happen if the fan clutch didn’t disengage (and the fan kept running at belt speed), say for 16 hours at 75 mph?


"what symptoms would I experience if my tranny does start to overheat?"
In the best case, your overdrive off light would start to flash and/or check engine light would come on. In the worst case, your transmission would fail.

"what would happen if the fan clutch didn’t disengage (and the fan kept running at belt speed), say for 16 hours at 75 mph?"
The noise level would be higher and your gas mileage would be decreased slightly. There would be no harm at all to your vehicle.

Thanks, I appreciate it!

Just wanted everyone to know we made it home to Austin no problems. However today I noticed the fan racing when it never would have raced before, so I’m still suspecting something. It’s almost time for the 100K checkup, so maybe changing the coolant might fix it. Who knows.

Side question - am I reading my service manual right? I don’t need to change my automatic transmission fluid/filter until 150K miles???


Do yourself and your transmission a favor and change the transmission fluid every 30 thousand miles. That means a pan drop and filter cleaning, NOT a flush.

Yes, that is the recommended (by Ford) interval for Mercon V used in the no dip-stick transmissions.
Many here will insist that you must still do it every 30K, just like many insisted that oil changes had to be every 3K when the intervals were changed to 6K or more. Oils and engines changed. Transmissions and transmission fluids have changed too.
I don’t know if 150K is alright or not yet, but I’m keeping an open mind on it. (Sort of, I’ve been doing full exchanges every 75K miles. So far, no problems.)

Thanks — when you say you have been doing full exchanges, you mean the flush or just the pan drop?

Heh. Believe what you will, tardis. I’ve seen these transmissions burn up well before 150K. Many times very low on fluid. With no dipstick, and the fill hole near the hot exhaust pipe, this design truly SUCKS!!!

The 30K mile service may sound excessive, but a pan drop and fill will cost about $40. A fluid exchange will cost under $100. A replacement transmission will cost $3,000 and up. That buys a lot of fluid exchanges!!!

I have a 2000 Explorer, one of the last with a dipstick. It gets 30K mile service and has lasted 202,000 miles so far.

Well, I’m coming up on 100K, like I said, so it’s an easy decision. Any reason why I wouldn’t want to do a full exchange / flush?

Is this one of those things it’s better to do at the dealership, with Ford fluids, or does it matter as long as it’s Mercon V or equivalent?


I used Castrol Mercon V for the last two fluid changes.