I have read quite a few threads on over heating issue but wanted to post my exact symptoms in case someone else has had same and found a fix.

Over past couple of weeks temp has started dancing around edge of 4th line just shy of the red. This happens on highway and I drive around 60. If I turn on heater it will drop down about half way between the 3rd and 4th line. Turn heat off and ot goes back up shy of 4th line. In town it actually stays about halfway between 3rd and 4th but if I come to stop it will move up. If I put in Neutral and hold rev to about 2200 it drops to near the 3rd line. Also I drove uphill from Bakersfield to Tehachapu, which is probably a solid 20 miles of uphill. I kept it in 3 and rpms around 2800 with heat on and it stayed just below 4th line. Heat off and it would have find into red. Heat on and in D it would have as well.

Not sure where to start. Flushed and bled system but no improvement.

 

"lines" probably aren't as accurate as an IR temp gun, try that first.

btw there is no real "starting to overheat" once it's cooked, well.

 

James, first, do verify the temps with an IR thermometer.

That said, the fact that it varies with RPMs suggests either the fan clutch or the water pump itself.

The fan clutch is a bit of a bear because there is no reliable test for them.

The water pump can have its vanes corroded to the point where they aren't moving much water.


My life is in vane!


Neither component is horribly expensive. Really, the simplest thing to do at this point is to just replace both, and you might as well do the thermostat while you are messing around there. Some on this forum have said you can replace the entire cooling system (radiator, hoses, fan clutch, thermostat, temp sensor) for around $200 bucks and then you know it's working.

 

How many miles since your last rad? 100k is about right IMO.