My radiator cooling fan isn't working, can't figure out!

Post by **jt74** » 23 Aug 2011, 23:08

I think I may have a blown head gasket. It doesn't smoke, doesn't leak, runs fine, but overheated.... again. Everything in the cooling system is brand new aside the fan, which is working. It just gets too hot and the coolant boils out.

cbsharon · Post by **cbsharon** » 12 Sep 2011, 00:54

Hi All. I've read through this entire thread, but I still have a few questions. Today for the first time ever when I shut off my 1992 740 wagon the cooling fan continued to run even though the car was shut off. It seemed a little strange, but I have driven other cars that did the same so I just went on in to work. When I came out my battery was dead (guess I shouldn't have left with cooling fan still running). I jumped my car and the fan immediately started back up. After some driving I shut off the engine and the fan continued. So I checked the cooling fan relay and as long as I disconnect any one of the three connectors from the bottom of the relay the fan stops. But as soon as all three connectors are back in place the fan immediately starts back up. Even when the engine is cold. Any suggestions? Is this a bad relay? Is it a bad ECU (also, can someone explain how I would go about replacing it if it is the problem)? Another thread mentioned a coolant temperature sensor, coudl that be it (similarly, where is that located and how do I replace it)? I also saw a mention of the ACC control unit maybe causing the problem (is that possible, also where is that located and how do I replace it)?

Thanks in advance for any help you can offer!

Post by **Auburn T5** » 15 Sep 2015, 09:09

Sorry to bump this ancient thread but I think my fan motor is toast.

I recently replaced my radiator and added the IPD transmission cooler, got everything put back together and had the car idling in my driveway with the heater all the way up to get coolant cycling through the system to bleed out the air bubbles.

I was tidying up some wires that run across the top of the cooling fan shroud and noticed that the black wire coming from the motor was hot.. as in it literally burned my fingers when I grabbed it.

I then noticed smoke and it had a distinct electrical burning scent. I shut off the car and walked away for a few minutes absolutely furious.

When I came back, the fan itself was extremely difficult to spin so I'm assuming the motor is seized up and caused the burning smell?? Not sure why that wire was so hot though? It's this single wire shown in the pic below. I'm actually impressed that the wire coating had not melted. That's how hot it was.

Post by **shiloh51933** » 18 Sep 2015, 06:21

Auburn T5 wrote:Sorry to bump this ancient thread but I think my fan motor is toast.

I recently replaced my radiator and added the IPD transmission cooler, got everything put back together and had the car idling in my driveway with the heater all the way up to get coolant cycling through the system to bleed out the air bubbles.

I was tidying up some wires that run across the top of the cooling fan shroud and noticed that the black wire coming from the motor was hot.. as in it literally burned my fingers when I grabbed it.

I then noticed smoke and it had a distinct electrical burning scent. I shut off the car and walked away for a few minutes absolutely furious.

When I came back, the fan itself was extremely difficult to spin so I'm assuming the motor is seized up and caused the burning smell?? Not sure why that wire was so hot though? It's this single wire shown in the pic below. I'm actually impressed that the wire coating had not melted. That's how hot it was.

sounds like u said motor is seized but I'd jump it first to see if it will come on.

breethlife · Post by **breethlife** » 27 Apr 2016, 17:20

I have already replaced the relay in my car I've also rebuild my engine I've also tested the temperature sensor and my thermostat is good my cooling fan is for some reason only turning on whenever my car starts to get hot and then all the sudden it'll get hot and spew water and then my cooling fan will decide to start working could it be faulty wiring faulty fan what do you think

Sommerfeldt · Post by **Sommerfeldt** » 27 Apr 2016, 17:23

Better start a new thread in the 740 forum, breethlife.

https://www.matthewsvolvosite.com/forums ... um.php?f=2

- S

Post by **98v70dad** » 28 Apr 2016, 07:41

When I did the PCV mod I was careful not to over-tighten the bracket that the intake manifold sits on (located on the forward side of the engine). I was careful because of the aluminum block. About 6 months later when warm weather hit my engine was overheating because the fan wouldn't come on. It never made it to the red zone but it was getting plenty hot. Turns out the fan wasn't coming on because it wasn't well grounded. I think the ground location is on the bolt that fastens that bracket. If you've recently done the PCV upgrade or had that bracket off you might want to check the ground.

Post by **shiloh51933** » 28 Apr 2016, 16:45

breethlife wrote:I have already replaced the relay in my car I've also rebuild my engine I've also tested the temperature sensor and my thermostat is good my cooling fan is for some reason only turning on whenever my car starts to get hot and then all the sudden it'll get hot and spew water and then my cooling fan will decide to start working could it be faulty wiring faulty fan what do you think

Jump the electric fan to see if it works every time you apply 12V to it and go from there.

wholesaler55 · Post by **wholesaler55** » 03 Apr 2017, 17:19

Hi everybody, I'm new to the forum but have relied on the great info you provide for a couple of years. I've ran into a problem that is very puzzling after changing my thermostat in my 2001 xc70. My temp Guage was not coming up as normal and the old t-stat was broken so I replaced it with factory part. The bleed hole is in front at the highest point (learned the hard way), and am getting the upper and lower hoses hot (upper much hotter). I noticed that no matter what I did, I could not get the radiator fan to come on but ac fan kicks on and off as normal. The car would not overheat but the heat flowing into the car thru the vents wad WICKED HOT. I unplugged the coolant temp sensor and the radiator fan came on immediately. I figured I needed a new cts, so I replaced that with a factory part also. Still radiator fan does not come on, even after a quick test drive and letting it idle for an hour! I know it's getting too hot by touching the hoses and motor even though the Guage shows a normal temp and the heat thru the vents is still extremely hot. I'm afraid to drive the car with the radiator fan not coming on and any help would be greatly appreciated.

Post by **Ozark Lee** » 04 Apr 2017, 17:31

I can't speak to the 01 but on the P80 cars, up to 2000, it is almost rare for the cooling fan to come on unless the air conditioner is running. The only time I have it come on otherwise is either after I have been stuck in traffic at a dead stop for several minutes or after some very spirited driving on a hot summer day.

...Lee

My radiator cooling fan isn't working, can't figure out!

Re: My radiator cooling fan isn't working, can't figure out!