Problem with coolant flow?

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It runs the fans a lot.
The fans run a lot at idle due to the low flow from the coolant pump due to low RPMs.

I don't sit and idle in traffic a lot, but what I do is pulse and glide. When I pulse and glide the car fans appear (unconfirmed at this time) to be running.
The fans run becomes the temperature sensor is hot.
It's hot because there's not a great amount of flow coming from the pump at lower RPMs.
To increase flow would mean to increase RPMs, and therefore affect fuel economy.

The test I did today was pulse and glide and simply watch the gauge, the gauge rose.

I then held the RPMs up with 0 throttle rolling down hill and as expected the temperature dropped below it's standard operating temperature.

Essentially the problem is the pump doesn't flow enough coolant through the thermostat if the RPMs are low, the fans run but as they are controlling to a sensor in the coolant before the thermostat, they are trying to cool with no coolant due to low flow.
I'd love to be able to monitor coolant flow, and show the problem but the above driving shows the issue.

The fix is of course to increase flow so that pulse and glide doesn't get a lot of heat, and the fans are off more (thereby fixing the fuel economy).

Since I only filled up recently, I'll be testing fuel economy with no pulse and glide this tank, to see if the increase in fuel due to no pulse and glide is measurable (giving two results in theory - how much does pulse and glide really save me).

[Frank Lee]

Maybe it has a plastic water pump impeller that has disintegrated- happened to Moon Unit. I'd never heard of that happening before and gee was that fun to diagnose and fix. :/ The replacement pump has a cast iron impeller LIKE IT SHOULD.

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Nah the impeller wasn't plastic - I replaced that pump when I replaced the timing belt, just weeks after I got it.

[ron]

then check it it may have been manufactured with the wrong rotation. for standard belt and is reversed with serpentine belt

[2000mc]

i'm not sure i really understand what all is going on.

i was hoping you could try to list out all of your symptoms, what you can see or hear, and when it does what. without listing possibilities, or likely causes.

"hot" might not be sufficient information, 190 or 230 i would consider hot, but the difference is huge in looking at cooling issues. and you might have to get some sore of scanner to see data.

any dash lights on? or dtcs? i think a car being P&G'd could potentially set a p0128, and command on the cooling fans. could there be a coolant level sensor at play? revving the engine might get coolant to the sensor and when at idle it commands the fans on.

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Well I ran the entire tank with no pulse and glide, and so the temperature sensor was down.

The fans are on when it's not hot, but I can't tell if it's speed related (i.e. if I am idle and barely moving the fans come on).

I realise I need numbers to discover the temperature that is being seen, but I've only just got a circuit together that can talk the proprietary Mitsubishi Protocol (OBDII isn't supported).

It appears I can get the temperature of the coolant from that.

I figure we should change the control of the fans and replace the Mitsubishi fan controller with my own (using an arduino). I know the thermostat opening temperature is 82 deg C.
I know it's fully open around 12 deg C above that.
I know the fans must run when the thermostat is open.

The fans I don't believe (am I wrong?) should not be running, if the thermostat is closed* - but they appear to be (see this is why I need the coolant temp and fan running status - to prove they run needlessly).

* - Except when the A/C signal is on for condensor reasons, but I don't normally use A/C.

[ron]

ever think its time to (i hate to say it) go to a good mechanic for a check only on the scope, or just change all the related components yourself at the same cost. Before the engine gives up from overheat related problems

[mloveland78]

Have you replaced the fan controller yet? I would be very interested in an arduino fan controller. I am in the process of replacing the belt driven fan on my Mercedes C220 with an electric fan and possibly an electric water pump. I was thinking of using an Arduino to control it but I have no experience with that platform.

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Yeh - the fan controller works good.

The existing fan controller received an input from the ECU about how fast / slow to modulate both fans.
I picked that input up and put two relays in (one on each fan).

It wasn't overheating at all, the controller was definitely running when no fan was being called for.

Fuel didn't seem to get affected too much, so it must not have been running all the time, but still - fixing it was better.

As to your issue - some things to think of.
- Removing the belt - does it have other pulleys on that belt? Finding a belt suitable is a consideration.
- The fan running all the time means that you only have the thermostat's opening temperature as your possible setpoint for operating.

You'll need to find some wiring for the ECU - you'll want the pin that has the coolant temp and buffer it off so you can get that as an input. Calculating temperature - you'll need to find the temp sensor's scaling to find it's temperature.

Air con pressure switch - since the fan is belt driven, there probably isn't an input for the AC high pressure to run the fan for condenser. You'll need an input for AC high pressure to run the fans.

Fault scenario - your sensor is open circuit - run the fans.