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I have a 79 Bronco with a 400. I have a problem with the engine overheating while traveling on city streets. The engine will run cool and then hot for a little while. Then it will go cool again and stay like that. I have replaced the clutch fan w/ a flex fan, thermostat, new coolant. Looking for help to solve the problem. I know that a shroud cover would help, need help locating one. Any info would be great. Thanks.
Could also be the instrument cluster voltage regulator, really a wire wound resistor, behind the instrument cluster.
If the oil and fuel gauges also seem to read incorrectly when the temp gauge reads 'hot', it's probably the voltage regulator covered with dust and partially shorting out under humid conditions.
I had a double whammy with my '79 several years ago. The instrument voltage regulator causing false readings intermittently, AND unknowingly I had a fan clutch going bad. Ultimately, I replaced the clutched fan with a standard fan.
The voltage regulator resistor cost me about $17 at a Ford dealer, and it's a plug-in unit like a panel lamp and a pretty simple DIY twenty minute job.
You should be running a 195 degree thermostat. There's a lot of other good suggestions here too.
You might want to put in a real temp gauge, too. They're very easy to install, I have both an aftermarket temp gauge and oil pressure gauge in my truck, and they're worth it. The stock Ford gauges are pretty lousy.
If it really is overheating, you might try a cooling system flush. You can do it in your driveway in about an hour with a kit from autoznne and a garden hose.