[2001 V70 2.4T] Occasional coolant reservoir boilover

[abscate]

That looks like normal temperature cycling to me.

[jonesg]

Compression in the coolant bottle when engine is completely cold might point the way to the next test.

[prwood]

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Kind of read this thread quickly but did you check to see if the fan is operating?

(EDIT: I see you said you think the fan is working. Double check as it is winter and the radiator temp could go down as you drive then back up while stopped.)

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I remember seeing somewhere that there were certain conditions that should force the cooling fan to turn on. Does anyone remember how to do that? Maybe it was running the AC or something like that? If so then I could test whether the fan and fan control were working.

[MoVolvos]

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That's correct, turning on the AC would cycle the fan. Have the temp setting at low. If the fans work you are in good shape, however you still need to make sure the circuit that kicks it on normally without the AC is also working. Never had to test that so of no help sorry.

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[prwood]

I just tested this out, and it seems the fan is *not* working properly. I turned AC on, set blower to high, and set climate control dials to coldest setting. The engine cooling fan did not come on at all. I did notice that the AC compressor was only cycling on for a few seconds every minute or so, not sure if this would affect the behavior of the call to the engine cooling fan.

I checked the main power connection for the cooling fan and it was secure. I also connected the signal wire connection and it was also secure. That being said, I have had to re-wire the signal connection for the engine cooling fan a number of times (the wire has been severed twice), and it is possible it could have a crimp or a break in it somewhere. But there was nothing obvious as there has been in the past.

Is there a fuse or relay for the engine cooling fan? I looked at the fuse box listings and didn't see anything listed as such.

Next test would probably be to use a multimeter to see if there is voltage getting to the cooling fan's main power supply cable, and then also testing the signal cable to ensure a signal is being sent when the cooling fan is called to turn on.

Any other suggestions?

[prwood]

I just ran some voltage tests on the engine fan connections. I'm not sure of the proper way to measure, so I tried a few different methods:

Main power supply cable:
Across terminals on supply side 13.4v
Across blades on receiver side 2.5-3v
Red supply-side terminal to red receiver-side blade 11.8v
Black supply-side terminal to black receiver-side blade 3.8v
The above measurements were constant at all times

Signal cable (this only had one blade/terminal, so I just measured at the blade and the terminal):
11.9v when ac running
12.3v when ac not running

The cooling fan did not come on at any point during my testing. Obviously it wouldn't if the cables were disconnected, but it also didn't when everything was connected and the AC was running.

Based on the above, it seems to me like the proper voltage is being sent on both cables so that the fan should have everything it needs to run (I am assuming the signal cable is supposed to go low when calling for fan), so I'm wondering if my next step should be to test the cooling fan itself. Any suggestions how I could go about doing that?

Also, not sure if I should put this in a separate thread, or how directly related it is to the problems above, but I also saw, for the first time ever, some coolant pooled on the ground towards the rear of the transmission. I am not sure of the source of the leak, but it was dripping from the rear of the transmission). I have never had a coolant leak or seen coolant pooled in this area before. It seemed to show up after I had been running the engine for a while, then switched the heat on as the ECT temperature had reached 205F. I'm just wondering if this is a symptom of the coolant being hotter than normal, and perhaps pressure seeking another outlet after having replaced the coolant reservoir cap and tightening it down more securely than previous. Photo below:

[jonesg]

The coolant might be coming from the radiator, check the plastic drain plug. I'd try touching it to see if its wet.

If you run the defroster with heat on , the AC will power up to provide dry air to the windshield and fans will run, or should.

[prwood]

The coolant might be coming from the radiator, check the plastic drain plug. I'd try touching it to see if its wet.

If you run the defroster with heat on , the AC will power up to provide dry air to the windshield and fans will run, or should.

Just checked the plastic drain plug. It was dry, as was the area around it.

Tried running the AC with heat and defroster. The engine cooling fan did not come on.

[jking4020]

It's probably your fan module. It's a metal looking plate right next to the fan motor. Mine went bad and then finally just stayed on until I had to unplug it. I just ended up splicing the wires and ran them to a toggle switch on my dashboard. 40 amp fuse in line with at least 12 gauge wires or bigger.that's only because I'm cheap and did not want to get a whole new fan housing cuz you cannot get the module by itself. This all happened after I was pissing coolant out of a hot expansion tank like you were.

[prwood]

It's probably your fan module. It's a metal looking plate right next to the fan motor. Mine went bad and then finally just stayed on until I had to unplug it. I just ended up splicing the wires and ran them to a toggle switch on my dashboard. 40 amp fuse in line with at least 12 gauge wires or bigger.that's only because I'm cheap and did not want to get a whole new fan housing cuz you cannot get the module by itself. This all happened after I was pissing coolant out of a hot expansion tank like you were.

Thanks. Can you provide any more detail on how you hard wired the switch for your fan? I may be interested in doing something like that.

So here's the confusing part - yesterday and the day before, when I was trying to force the cooling fan to come on, it did not come on at all no matter what I tried. Tonight, it came on, when I was testing it by running the AC with heat and defrost, and also when I was running it on max cool. No idea why it decided to come on tonight and not the past two days. It appeared to cycle on for about 10 seconds every minute or two. The AC compressor was kicking in several times per minute and the cooling fan seemed to kick on after roughly every 3rd compressor cycle. The ECT temperature was at or under 195 during testing the whole time. Contrast with yesterday and the day before when I was trying to force the fan on using the AC, and the ECT temp got up over 200, with the fan not coming on at all.

Does anyone know what ECT temperature is supposed to trigger the engine cooling fan to come on in situations where the AC isn't running?

Given the erratic behavior, it would sort of make sense that the fan module is going bad, since I believe I've verified by measuring the voltage that the fan power and signal are being sent properly.