Cooling issue

[FordPrefect]

alrighty, got a bit of an issue.

so my 77 has been running hot enough to worry me, especially when stopped at lights. a couple days ago, when i got home from work, i let it sit in the driveway until steam was escaping and the coolant in the overflow bottle was boiling. yikes. lower radiator hose was cool to the touch.

i put in a new thermostat today (pretty sure it's oriented correctly, flange part to lower hose, machined part to water pump) flushed out the system with water (it all looked pretty clean) and put in a flush T in the upper heater hose near the firewall.

Filled her up with coolant/water as per instructions (from the T, burping, etc). ran it around the block, let it heat up in the driveway, and was happy to see the fan come on, lower hose was hot, and the dial stayed at a normal temp.

i got home from work, let it idle in the driveway for a while, and the fan never came on. heat climbed almost to the red, so i manually shorted the fan to ground to help cool it then shut off.

what gives? bad water pump? stubborn air bubble?

[joelittel]

Air bubble is my guess.

When I have a stubborn one I’ll message/squeeze the hoses to help move it along. There have been times where this was necessary to do more than once.

I like to keep the radiator cap and bleed screw on tight, only leaving my filler T cap open while squeezing the hoses. This way I can watch the bubbles come up and out. When I get a few out I slowly pour more coolant it. Then repeat, squeeze all the tubes, force bubbles out and slowly add more coolant.

My car requires less burping when I slowly fill the coolant, as in a slow trickle. This takes a while but seems to avoid trapping air in the system.

[seabeelt]

I’m starting to have the same issue with the fan not coming on. Runs fine in the normal temp rang when the car is moving but will start to climb when I filing or sitting in traffic. Haven’t had time to check but I suspect eithe the sensor in the rad or the relay that controls the fan. Have to order parts anyway so I may just get both