BMW 3 F30 Thermostats & Housings

The BMW F30 330i and 335i are well-engineered machines, but if you're pushing power or running track days, the factory cooling system starts showing its limits pretty quickly. For the N55-powered 335i especially, upgrading to a Mishimoto performance aluminum radiator is one of the best investments you can make - it flows significantly better than the OEM plastic-tank unit and holds up far better under sustained heat. Pair that with a Mishimoto or CSF charge air cooler to keep intake temps in check, particularly if you've got a tune or bolt-ons. The factory coolant expansion tank is notorious for cracking on higher-mileage F30s, so swapping it for an Rein Automotive or genuine BMW replacement is cheap insurance. For the water pump, stick with an OEM-spec unit from Graf or Saleri - the electric water pump on these N20 and N55 motors fails around 60,000–80,000 miles without question. While you're in there, replace the thermostat and all coolant hoses as a set. Don't cut corners on cooling - overheating even once can crack a head gasket and turn a cheap maintenance job into a four-figure nightmare.