One problem related to coolant leaking has been reported for the 2013 Toyota Highlander. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2013 Toyota Highlander based on all problems reported for the 2013 Highlander.
Head gasket cracked, leaking coolant into 5th cylinder. The reason for a po305 misfire code on reader. Auto shop removed head gasket and saw that the finish on the engine block was horrible. They called Toyota themselves to file a complaint and have them replace that side of the block. Auto shop doesn't feel comfortable replacing head gasket without Toyota fixing the finish. If the finish is as is, head gasket will eventually crack again. Highlander was bought brand new and only has 73k miles.