QuestionWe're having a problem with overheating. It gets hot when you drive it, but then if you kick it down to a lower gear & higher RPMs it cools down really fast. The fan is hotwired. When it idles, it'll peg out hot, but the radiator remains cool. It acts like the thermostat is not opening, but we've changed thermostats twice and flushed the system. The water pump's not leaking, as far as we can see. We suspect maybe there's a cracked head or block leaking compression into the cooling system. Do you have any ideas? Thanks so much!
AnswerHi,Mike
Sounds like your having a flow problem through the engine block to the radiator,this may be a sign of a failing water pump,i have seen the impeller of the water pump deteriorate to the point that it no longer flows the amount of coolant,then at higher eng speeds it is able to flow enough,also try removing the Tstat and run the vehicle and see if it begins to overheat.
If you suspect the eng block,heads or headgaskets,there is a exhaust gas analyzer kit the parts stores such as NAPA have it and it consists of a blue bottle of special dye that reacts with exhaust gas and a contaner that fits over the radiator fill neck,its inexpensive and will tell you if there is a problem with exhaust gas entering the coolant,let me know what you find,Thanks
ED
