Sudden change in engine temperature

[CarlG]

The engine temperature started running 30 or 40 degrees F above normal one day last week and has stayed up there every time I drive it now.  It began first thing in the morning, (I had driven the day before with no problems, the outside temperature and humidity were about the same both days), by running up to near the red and then going down to about the mark between 180F (where it normally runs) and the red mark and staying there.  This was with the AC on but switching it off did little to improve the situation.  I checked the coolant level and had to add a small bit but it made no difference.  I tightned the fan belt but again it made no difference.  The oil level was ok. The car is still running great with no strange noises.  Any ideas on why this sudden change?

[graphic66]

Thermostat stuck?

[CarlG]

I guessed it was not the thermostat because the temperature went up for the first mile or so, then went back down, just not all the way down.  I assumed that meant the thermostat was working.

[Raymond]

How far above normal does it stay?  Does it get cooler if you slow down after driving fast?  That might indicate a partially clogged radiator.  When's the last time you flushed the system and added fresh coolant?

[CarlG]

It stays 30 - 40 degrees F over normal.  (Normal is just under the 180 mark).  It does not cool down upon slowing down.  Good question on the last flush and change of coolant, it may be 5 years or so.  But why would a partially blocked radiator suddenly show up?  Having said that, a radiator shop does not need to specialize in these cars so I could get it rodded out and new coolant anywhere locally so that and a new thermostat would be easy places to start.  I have two questions

1. What are the signs when a water pump goes bad?
2. Could it possibly be a blown head gasket or something more serious?  (Remember I have seen no change in the way the car runs).

[seattle_Jerry]

When was the last time you replaced your water pump? At $100 its also cheap insurance against an overheat from pump failure.

If the pumps bearings are what fails, it makes a bad noise. There could be problems with the internal vanes from rust that reduce pump efficiency while showing no outward signs of failure.

Remember that if it starts getting too hot, turn on the heater. The heater core is basically a mini-radiator. The increased coolant flow can reduce the temp enough to get you out of the danger range and to a gas station.

Other causes are a dirty engine and needing a tune-up.

Check your radiator fluid for oil and see if it smells funny.

I'd think you would see a difference in exhaust color if you were burning radiator fluid.