Hey everyone. New to this forum.

I have a 2013 Mazda 3i 2.0 Skyactiv engine. For about two years now I have been noticing a strange overheating with a strong burning smell. However, it only happens in the heat of summer and after climbing a significant hill. Neither the temperature warning light nor the check engine light have ever come on and no diagnostic codes have been triggered. The heat and smell clearly generate from the central back area of the engine under the windshield - right about where the upstream O2 sensor is and the exhaust manifold. The smell is not coolant, but more electrical/rubber.

Here's what I have done so far. A trip to the mechanic ended with a new alternator who said it was running hotter than normal. No fix. I have put in new O2 sensors both upstream and downstream. No fix. I have flushed the cooling system and installed a new thermostat. No fix. Once again this only happens in the heat of summer and only after climbing a significant hill.

Anyone have any ideas or suggestions?

Thanks, Mitch