2016 CX9 coolant level mystery
 

Hi , I have been the proud owner of a 2016 Mazda CX-9 since June. The car has covered 59K miles and runs very well BUT it needs frequent top ups of the coolant liquid.
By that I mean that in order to keep the liquid at the Full level in the plastic tank next to the radiator I've had to add approx. 1 pint of coolant every 1K miles.
There are no obvious leaks and no sign of any coolant in the oil so this feels like a bit of a mystery. Is this normal? Has anyone seen this before ? Any suggestions? Thanks.

The first thing to do... Have your cooling system pressure tested

It should be at the full level only when hot. If you fill it when cold it may expand normally and overflow when hot. So--try filling only to the mid point between high & low when cold, then check it when cold and see if there is any loss.

This would not be the best advice given the information in the OP first responses. Generally, if the year build was prior to about 2005 ish (actually a little older years but same at 05 and newer for argument sack) the old school thought about coolant reservoir amounts would be excellent. I do realize that manuals as well many internets information still seem to be old school information about filling. If the ECU ,engine and transmission and associated control parts are all inworking order you really should fill the reservoir to the top line cold or hot. Those reservoirs are design to hold the capacity of normal fluid expansion and technically speaking if they are expelling coolant then something is not as it should be.

I recommend based on the limited information should be the first test procedure in my response earlier. Inspection for a leak in small amount of coolant will dry without always being easily found evidence unless a examination in a semi dark area or room and a good flashlight is used. On the MAZDA such an inspection would likely require removing the plastic under guard as well.

thank you both I will get the system tested..