Reader Question: My 1992 Chevy Step Van P-30 5.7L Auto Trans AC engine will not reach operating temperature. I have already changed thermostat. 195 Stant Superstat. Coolant condition is ok. I have checked fan clutch turned freely engine cold and warm. No codes stored, only 12 displays.
I think gauge is accurate. Too many other symptoms – excessive fuel consumption, heater not as hot as used to be, and more exhaust smoke, does not run as well.
Recently, it passed the state emissions. I know it would not now. It just started problems recently.
Is it knock sensor-retarding time or distributor worn? The truck has 120k new plugs wires cap rotor and air filter within last 25k.
I would start with the basics first. When the engine is or should be at normal operating temperature after driving awhile, feel the upper and lower radiator hoses. They both should be very hot to the touch and you really should not be able to keep your hands on them for very long.
If the lower hose is much cooler than the upper hose, I would suspect you might have a restriction in the radiator, or a lack of circulation problem like from a water pump that the impeller has been completely rusted away…..rare, but I have seen it a few times.
Place your hand at the top of the radiator and slowly move down the center, if the radiator has a cold spot in it, you are going to need a new radiator.
Feel the intake manifold as well, you are trying to find a restriction….if you have a laser heat gun that works best, but you can just start feeling everything with your hands, starting at the radiator and moving towards the engine looking for the hot to cold line. Both heater hoses should also be very hot as well.
Do not get fooled by a faulty gauge or a bad temperature sending unit giving the dash gauge faulty info. If you do not have access to a laser heat gun, put a thermometer in the radiator and check the accuracy of the dash gauge.
When in doubt, replace the cheap and easy to replace temperature sending unit just to rule it out.