2 days ago with the A/C on high and 90+ outside temp my gauge(original cluster gauge) would read about 180 at all times. Yesterday it ran about 230 all day, with the A/C on. Today I changed the thermostat with a 195 degree unit. It takes longer to heat up today, than it did yesterday, but it still does. I noticed the gauge would <i>jump</i> from 190 to 230 hang there then move up to 240 then creep towards the 260 mark until I turn off the A/C and turn on the heat when it would come back down to 220 - 230. This is while driving 60mph. The A/C cools great until the temp reaches 240+<P>
The air damn is in good condition.<br>
It has a single radiator cooling fan, that comes on with the A/C on or cycles at the appropriate temps with the A/C off.<br>
As said above, I changed the thermostat.<br>
Not very scientific I know but, I ruled out a faulty sending unit or gauge because the coolant tank fills more anf more the hotter it gets. I can cool the motor down by spraying the water hose over the radiator for a few minutes and the gauge will come down and the coolant in the resevoir will recede to correct levels.<BR>
The system appears to flow well and has been well maintain (as best my visual inspection can tell)<br>
Radiator has no apparent corrosion or damage.<br>
No obstructions that I can tell.<br>
Fan is pulling a good amount of air through the radiator.<br>
Timing is adjusted correctly. (checked with a timing light, with the ESC disconnected.)<br>
Heater core is new.<br>
I changed nothing between the time it was running cool and when it started heating up.<P>

Could the fan motor be wearing out and flowing insufficient volume?<BR>
Could this happen "overnight"?<br>
What am I missing?

 

I think you have the right idea of the fan motor. My 89 Bird was doing the same thing last year and I changed everything under the hood to do with the cooling. Till I finally came to the fan motor. After I changed it I could really tell the difference in the Flow.

Also have you checked out the condenser? I had to replace mine because it had flat spots in places. After all the changes my Bird hardly goes above 180 running the A/C in 100+ degree weather. You may also want to wash out the fins on your radiator/condensor. You would be amazed at how much junk comes out of there...

Lates,

Demo:hail:

 

Thanks for the response. I went ahead and changed the fan motor. Went for 12-15 mile drive, with traffic lights. The temp gauge needle hung between the 2's in 220 just like it used to. The volume of air doesn't feel like it is much different. This seems to indicate that the volume of air from a good condition stock single fan is the minimal amount needed to keep cool. A small degradation in cfm and you get hot. Perhaps I need to look into a higher cfm fan setup to keep beyond the minimum.