I'm experiencing a problem with my 89 Sierra 5.7L TBI.
Here's what I've replaced within the last 30 days: Radiator Radiator Cap Upper & Lower Hose Thermostat Water pump Coolant Temp Sensor on intake manifold
There are no leaks. Or at least none that I can find.
Here's the problem: The truck heats up to operating temp, and then continues up to 260F. The "check gauges" light comes on and then about 30 seconds later, the temperature drops to 210 (normal)...and then operates just fine. Occasionally, I will hear gurgling in the heater core, but not consistently. Sometimes it happens when the engine is hot, sometimes when it is just warming up and sometimes it doesn't happen at all. The reservior remains full.
The oil was just changed about 2 weeks ago and is dark. I can't find any traces of coolant in it.
Does anyone have any suggestions as to the cause? Could the guage itself be malfunctioning? Any help would be appreciated.