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post #1 of 14 Old 11-24-2018, 06:09 PM Thread Starter
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Cooling fan runs too long I think

Hi All, I have a 2009 Versa 1.8L six speed. The radiator cooling fan runs what I think is far too much. It's not on continuously, and takes quite a while before it comes on (perhaps 5 miles of regular driving), but after it's on, it hardly ever shuts off. In particular, if I'm driving highway, where I would expect the air movement to render the fan unnecessary, it still doesn't turn off. On the other hand, sitting in traffic, it might. It does not, however, seem to boil over, although I'm anxious because it's the cold season here in Colorado, and when we get to Summer again... Well, you get the picture.

I have attached an OBDII monitor to this while driving, and what I see is the coolant temp slowly climbs (fan is off) till it reaches about 100C. Around about there, the fan comes on, and then with the fan basically running continously, regardless of driving conditions, the coolant temp will vary between about 101 and 106 at the extreme, staying mostly in the range of 102-104.

Now, I see that there are two thermostats sold by local stores for these cars, one with an opening temperature of 180F and one at 200F. I believe that these two are both used in the same engine (one controlling the cabin heat), but the 2009 Versa manual shows a single thermostat with an opening temperature of 180F.

My suspicion is that the young lads who owned this before me probably put the 200F thermostat in when the replaced the radiator after a front-end collision they clearly patched up themselves.

Does this guess seem plausible to others, or is there a more likely explanation for this seemingly controlled coolant temperature that also seems to be higher than the engine computer wants it to be?

I guess another explanation would be if the thermistor that measures temperature is out of calibration and it's not really all that hot, but the computer thinks it is. But I'm not sure that a thermistor is a device (being a solid state electronic part) that's particularly prone to wandering calibration is it?

Any thoughts welcome; I have the thermostat coming ('coz it's cheap) but draining the system and replacing it will be a bit of a nuisance if there are other things I should be trying first...

TIA
Simon
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post #2 of 14 Old 11-25-2018, 07:18 AM
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Well, your temps look to be in the ballpark to me...............the two stats per car I would think would be somewhat different looking, The other one is the water control valve which is a stat too. Get parts stores to pull you both of them and compare. The 180 'stat' goes into front of engine likely with water coming into engine, the 200 one is water going out and commonly the 'water control' one. The lower number is just so that one is open before the other, the higher number one is the one that controls the temp of engine. That one should lead hose to the top of the radiator, the lower number stat comes off lower rad hose.

They both ARE stats no matter what they call them, the lower one I don't even know why they use, my Fords run the exact same water patterns and they have an open hole where the lower number stat goes, there is nothing there at all. Japanese complexity to me, you don't need the lower temp one I'm thinking. At some point I will be yanking that one on mine to see what happens, should be nothing.

Get gaskets for those too, don't reuse them even if they look good, they don't rebound to get thick like they used to be when new.
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post #3 of 14 Old 11-25-2018, 04:14 PM Thread Starter
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Thanks AMC! A little follow-up discussion if I may?

My version (the 2009 1.8L) is was designed/built with a *single* (the lower) thermostat. the upper one was a later addition to the design, apparently to get the cabin heat to work sooner. The one is mine is supposed to be the 180F opener. My particular thought was that if the two stats on the newer designs are the same size, the previous owners might have put the wrong one in, raising the temp at which the coolant in the engine block is released to the radiator, and thereby raising the set-point temperature.

My second thought is that if the thermostat opens around 180F, and is fully open (according to the workshop manual) at 95C (sorry for the mixed units!) should it not stabilize pretty close to that fully-open temperature?

But if you think that running steady at 102-104C is pretty normal, then the question becomes why is that fan running essentially continuously? I believe that it's controlled by the computer, right, so that tells me that the computer thinks that it's too hot (or at least "plenty hot enough, time to run the fan to bring this down", I suppose! Isn't the point of an electric fan that it only runs "when necessary" making everything more efficient than the older belt/crankshaft driven things that pulled air all the time.

I'm not running the A/C, btw!

Well, I guess I'm just musing, but any thoughts are welcome.
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post #4 of 14 Old 11-26-2018, 07:17 AM
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Relay sticking? It IS odd that it stays on that long at this time of year. Maybe temperature sensor.

FYI, virtually no engine on the planet runs at the exact stat temperature, they typically run 10-15 degrees warmer. The rated temp is only when the stat begins to OPEN, it is not fully open yet, that takes more heat to do it. They are never exact either, commonly being off 5 degrees from part to part. Just as a reminder 100C temp is 212F.

You are incorrect about not having two stats, the '08 and '09 1.8 MR service manuals clearly show that both are the same as the later ones. The 180 is in the casting above the a/c compressor, the 'water control', or second stat (200) is on the driver end of engine above trans bellhousing, it is under the water neck that the heater hoses go to. Again, that one is the one that determines the engine temp. I believe that Nissan does not call that second part a stat to avoid confusion, of course, it simply makes more. Look at the name........the word 'control' says that is the temp setting one and I can vouch for that, all modern engines exit the water high to take advantage of convection to ease the water moving through the block. Why the exit is always high and entry is low. The nomenclature 'error' causes more dealer work too and one reason why they do it. Money.

Last edited by amc49; 11-26-2018 at 07:45 AM.
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post #5 of 14 Old 11-26-2018, 07:54 AM
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https://www.rockauto.com/en/catalog/...hermostat,2200

Two different temps listed there, the 200 is the upper and the 180 the lower stat. The upper is also called the water control one.
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post #6 of 14 Old 11-28-2018, 03:17 AM Thread Starter
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Oh, well, that's embarrassing. I was sure that I'd looked at the diagram of the water outlet, and seen the absence of the control valve that I had seen in a later manual. Looking again... well, I guess I was hallucinating

Presumably, if the temperature sensor was overreading, the computer would turn the fan on, but the thermostat might actually be closed, preventing the fan from having any effect, yes?

So, perhaps I need to find an independent way to determine that actual temperature of the water in the block.

Does that seem like a reasonable next step, and if so, any suggestions on how to do it? I have one of those infra-red/laser non-contact temperature probes, but I have to assume that the temperature of the casing around the water outlet, or of the engine block, won't be a very good representation of the temperature of the water. Or would it?
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post #7 of 14 Old 11-28-2018, 08:49 AM
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The water control will NOT be sticking shut, that is stuck stat and the car overheats almost instantly even with fan working. The needle will go off into the red.

A laser if not a crap one will read the metal as close but not exact.
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post #8 of 14 Old 11-29-2018, 03:14 AM Thread Starter
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I'll try the laser, good to know it has a chance of being relevant! Thanks.
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post #9 of 14 Old 11-30-2018, 12:15 AM Thread Starter
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Well, I'm a little embarrassed that I didn't look at this first, but I suspect I might have found the problem. Image of the radiator is attached. I will say that I discovered after a rather hasty and ill-advised purchase that this car had been, for all intents and purposes, crashed. Some kind of front-end collision that involved driving over something hard and big (a foot diameter boulder, perhaps). This impact evidently bent the cross member under the radiator, and also bent the left side control arm (I think they were turning when they hit whatever it was.) But I think they also scrunched something into the radiator, as it looks like fully 1/3 of the fins are bent sufficiently to prevent any meaningful airflow. There's also a loose piece of plastic in there somewhere that partially covers (when it flops about into the appropriate position) about 1/5 of the radiator front surface.

Does my guess that this is the true cause of my problem seem reasonable? I think the thermostat and temperature sensors are working fine, and it's just that the system is struggling to cool itself effectively as it's running on 2/3 of a radiator...
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post #10 of 14 Old 11-30-2018, 01:14 AM Thread Starter
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Hmm, that's not the radiator, is it....? It's the AC condenser, isn't it. Presumably that's rather harder to replace, what with all the refrigerant and so forth, and needing to keep the system clean so the compressor doesn't get damaged.

Is this a horribly difficult thing to replace? Is it possible to remove it and "seal off" the A/C for a while (leaving it inoperative) while I work out if there's anything else wrong with the main/engine radiator and cooling system? Could I then put it back together with a new condenser and have someone recharge it?
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