Topic: 79 403 Running Hot

[jamesy_181]

Howdy! I'm hoping to get some help with my TA running hot. It is a stock 79 with a 403, aftermarket radiator (PO installed, not sure specs), new 160 thermostat, HD fan clutch, and located in hot hot Florida.

Lately when I'm driving around (40 mph - 55 mph) with the A/C on, the car quickly rises from operating temp (first tick mark to the right of 110) to close to 220. Once I shut A/C off, the car cools down in a minute or two. If I'm driving with no A/C, car doesn't get past 160 even when I'm hammering on it.

Something to maybe point out also is that the first time it overheated (hit around 230), I had a severe loss in oil pressure, prompting me to shut the car off and replace thermostat. Since then, oil pressure doesn't drop to a concerning level even as the temp approaches 220.

Any ideas as to what my issue is? Thanks in advance!

[Wallington]

Check the components one by one. The fan clutch may be failing or not the correct type, likewise if it still has the AC fan. If the radiator is unknown it may be clogging up as well as engine galleys. Do a flush, see condition of coolant and fins and what comes out. A second gauge or heat sensor gun may be useful but not at this stage. Does the aftermarket radiator still use the factory shroud for cooling? Just rule out the basics.

[jamesy_181]

Sounds like a good place to start, thanks for the help!

[Angelo]

Did you figure out the overheating issue? I bet it’s the clutch fan, I just went from the normal to a heavy duty clutch and it made all the difference.