Cooling system is making me hot

[dirtybob72]

I have been going over my 78 spider and the cooling system isn't making any sense. When idling and sitting still the temp gauge will climb almost to red line and the fan never comes on. I hot wired the fan and it won't cool down. When I disconnect the fan and drive the temp cools to 190, at red lights it climbs and cools back down when I start moving.


Does the thermostat housing come apart so it can be replaced or is it a unit?
Are sticking thermostats common?
What is the operating temperature range of the thermostat?
Are there changes that can be made to simplify the cooling system?

[dmwhiteoak]

Did you burp the system ? These cars are bad about keeping air pockets. Instal a flushing T in the line between the heater core and block. It makes life easier. The fan switch is located at the bottom of the radiator. Check it to be working properly.

[courtenay]

When the car is hot, feel the top and bottom of the radiator. If there is a noticeable difference in the temp between top and bottom then it is likely the thermostat isn't opening. If it's an external 'stat, then replacement is the only option - they can't be repaired. Same goes for an internal stat for that matter.
You might also want to check the "high operating temperature" thread below.

[124JOE]

ive heard about that before

open the heater core "to release air"
fill it up all the way
some people park it up a seep hill for that
run it,fill it
untill it wont take any more


some drill a 1/8 hole in the themostat disk
so air can move out

[dirtybob72]

Thanks, All good advice.I feel that I got all the air out and all is well.... accept the fan comes on at about 245 and shuts off after 10-15 seconds. this must be a bad switch. Does anyone know the limits of the switches.

[courtenay]

Bob - the switch and fan may be fine. It might be the temperature sender that "spikes" the needle. On my '80 Fi, there are two sensors in the block. The one nearest the radiator "spikes" the needle and the one nearest the firewall controls the gauge. Disconnect the wire to the one nearest the rad and see if the temp gauge works as it should. If so, leave it disconnected until you replace it. It isn't really necessary.
That's what I and several others have done. Follow this process before you start replacing expensive stuff!