hey all i have a 2002 vx commodore series 2 we were going away up the coast a couple of weeks ago and blew the heater tap so we found a spare parts store got one put it on bled the cooling system and was all fine on the way home it was going fine sitting on a 100km went to over take a car soon as it got over 110 it got hot and the warning went off pulled over let it cool down and away we went was fine untill we went over 110 again it over heated now is still doing it around town its fine out on the open road fine untill we go over 110 can any one tell me what it could be a mechanic told me it could be the radiator blocked with all the stuff from the block from when it over heated and has blocked it so said get if flushed or replace it and replace thermostate what do you guys reckon this mechanic is very good be doing it for 15 years and help or ideas would be great
You can check if its a plugged radiator by pressing the accelerator hard on the road while moving. Do it when the car is warmed up. Quickly press the accelerator and see if the temperature goes up. The higher the rpm, the more load on the engine, the more pressure on the cooling system. So if its plugged it will not be able to handle the extra pressure/heat and the temperature will go up. Another way to check if its the radiator is to unplug the top and bottom hoses and put a garden hose on the top of the radiator and see if the same flow comes out from the bottom. If the flow is little and brown crap is coming out then definately radiator. What engine you have? v8 ls1 or v6? Also check if there is a coolant leak. If there is one, then it could be that air is getting in the system through the leak. Thermostat is no problem because when it fails it just opens and its like you are driving without one. If the thermostat is bad, then the car takes forever to warm up. If your car warms up quickly then your thermostat is fine. v8 ls1 have an automatic bleeding system which can get blocked.
Did you bleed the system when you changed the heater tap? You could have a pocket of air in the thermostat housing where the temperature sender is causing it to read higher than the actual coolant temperature.
