One problem related to engine cooling system has been reported for the 2003 Toyota Tacoma. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Toyota Tacoma based on all problems reported for the 2003 Tacoma.
Leaky water pump discovered upon routine change of timing belt on 2003 Toyota Tacoma 2wd prerunner. Discovered complete lack of gasket and woefully inadequate amount of sealant apparently applied at factory. (no more than 1/8" wide after compression between water pump housing and engine block) engine continually used a small amount of coolant/antifreeze and over time had built up a substantial volume of sludge/crusty coolant around water pump housing and timing belt (crankshaft) pulley. Although absent in this instance, this build-up has the potential to break loose and fall between the timing belt and pulley and ultimately cause timing belt breakage. Replaced belt and water pump. Re-manufactured water pump is equipped with a gasket.