M16a headgasket

If you are not doing many long runs then the leaking gasket won't have much time to displace coolant into the expansion bottle, this is why I nursed my Jimny for nearly 3 years replacing various bits of the system along the way all the time believing that the m series engine doesn't have head gasket issues. However if you do go for a long run with it in this condition enough for everything to get properly warmed up then it will displace enough coolant to start getting hot. It's also worth noting that the temperature gauge is not linear, instead they show a steady central position between about 75 degrees and about 108 ish degrees they then climb very rapidly into the red by about 115 to 120 degrees they are best considered as nothing more than a light like a VW. As such it's entirety possible that the hot smell you are reporting is because it is quite a lot over normal operating temperature it's just a not reporting it on the dashboard. Ultimately with the m series engine once they start doing odd things with the cooling system the root cause is the head gasket especially if they get hot hot.

What you are experiencing is head gasket failure, it's quite early stages but it's head gasket related. When I had your symptoms I replaced everything with genuine, water pump, radiator x2, cap, thermostat, expansion bottle pipe, viscous coupling and fluid, the whole lot. It was only rectified by a new head gasket.

Martin in the shop in the top banner, genuine parts at sensible prices.