Why would you have an intermittent antifreeze smell in a '99 Tacoma?

waterpumps leak on these quite often. that's the first place i would check. if you don't see any signs of coolant leaks from that area (check just below and to the left of the thermostat housing) have the system pressure tested. i believe also that head gaskets leak on these (V-6 models) check for a trail of dry coolant starting above the stat housing at the seam between the head and the block.

Answer

also I know on chevrolets atleast the ones I have owned you might want to check your heater coil it is probbly under your dash board near your glove box just something else to check