Because the Nissan Titan radiator base reservoir is made from plastic. The plastic tabs which hold the radiator in place are part of the radiator housing and the transmission fluid cooling tank. Therefore, when the plastic tabs broke on the Titan full size work atruck (plastic tabs) the radiator lost the cooling fluid. Because the radiator lost the cooling fluid, the full size work truck with the plastic radiator became overheated. The truck made to tow things became overheated, therefore one of the head gaskets and or the heads itself(s) cracked. So I had to replace the engine or replace heads or gasket (same price). I replaced the engine with a certified used engine and upgraded the radiator with a real radiator (4 core) all aluminum radiator. The entire cost of all this work, beside having to deal with the (wife) spouse, repeatedly telling me to sell the vehicle. The total cost easily became over $6,000.00. This is not including the crappy transmission the full size (supposedly) tow vehicle that failed. The reverse stopped working on my Titian 5,000 miles after the warranty ended which would be at 60,000 miles.