I have a 2016 GX4HS (83k miles).
The coolant is bubbling.
The dealer I bought it from says it's supposed to but I haven't heard of anything like this from anywhere else.
Car does still drive well so maybe the dealer wasn't lying.
The mechanic said it was nothing to worry about, possibly a little bit of water in the system.
I haven't noticed any bubbling for a while.
Apparently it's relatively common with outlanders.
I would have assumed a leaky head gasket.
Any water in the coolant would boil at a lower temp than the coolant and produce steam bubbles.
But I believe the coolant is at about 90C, which is below water boiling point........
This depends on which coolant 'header' tank you're looking at. If things haven't changed since the 2014 GX4h, the square shaped tank on the left of the engine bay - quite high up, is the EV coolant which does wobble about and bubble a bit when the engine is running. I think this is distributed around the EV system by an electric pump.
The header tank lower down on the right (just below the conventional radiator cap) is the engine coolant. This could have some air in it, caused by the electric heater pump (which is a separate electrically operated pump, not the mechanical coolant engine pump) and its associated electric heater pipes/matrix which is very difficult to bleed air out of should any ever get in there (coolant change for instance, or trying to fix the heater). If the heater doesn't work at all well it can be caused by air in the system or the well documented (don't I know it!) blocked electric heater matrix. See elsewhere on this forum.
If head gasket leak or engine block crack is the cause it'll do it most of the time when the engine heats up. I'm not sure if you can have a 'mild case' of this - I've only ever experienced a fairly severe one (not on a PHEV though). The plastic engine coolant header tank will maybe become pressurised (blow the lid open on the plastic tank - I think because excess pressure getting past the radiator cap?) and hot and sometimes (but not always) have oil in the coolant or coolant in the oil. Engine would most likely overheat at this point too - although the PHEV doesn't run at the same revs as a regular petrol engine, so usefully doesn't have a temperature gauge to observe unless it overheats - in which case a warning appears. The correct Mitsubishi engine coolant for the PHEV doesn't - and shouldn't - have any water added to it, somebody may have done this in the past possibly? Does the engine coolant level change at all?
Is the coolant bubbling out of the engine reserve tank & into the engine bay or just recirculating?
The motor coolant is usually recirculated for a short while by an electric pump after the vehicle is switched off .
Maybe this is what the dealer is referring to and is confused as to which transparent reserve tank is which..??
