Water running/dripping down windshield

[Cyker]

10 hours ago, YarisHybrid2016 said:

As I understand the system, the coolant runs out of the engine, through the cabin heater block and back around. All that happens is a valve opens to let more or less coolant through the cabin heater block.

In the case the engine gets cold, the rate of water circulation reduces, until the water temp drops to a minimum defined threshold (the higher of cabin heat demand or minimum block temperature).

I have noticed that above 18-20 cabin temp setting, the engine starts earlier to maintain a higher temp. i.e., at 20, it will fire up at 1-2 bars on the temperature gauge; at max it will fire up at 3 or even run the ICE nearly continuously.

The fan seems to make a huge difference. If you sit stationary, or in slow moving traffic, have the heater set to 20 or 22, and the fan flat-out, it can prevent it getting warm at all.

I noticed on my Gen.3, and also on the Gen.4, if you have the blower set to demist the window (floor/windshield) or press the windshield button, it will be more aggressive at running the ICE to maintain temperature than if it is set to face or face/floor. Windshield only it is most aggressive. The end-result is it hits fuel economy quite hard if you have it set to demist only, high temp, and mid/high fan setting.

Setting floor/demist, 2-3 bars for fan, and 20-22, it doesn't try to run the ICE nearly as much, but remains just as effective.

I find the same with mine; The Mk4 really struggles to retain heat compared to the other hybrids judging by others experience.

I suspect it's because the engine block is tiny and has less mass than even the Mk4's engine, so it can't 'store' so much heat in the metal, and with the coolant loop sucking it out to heat the cabin it's really hard to keep the engine warm.

If mine is at its desired 4 bars of heat and I turn the heater on at 20C, it will drop to 2 bars within minutes and trigger engine start!