Overheating issues?

1997 FORD F-150
263,000 MILES • 4.6L • V8 • 4WD • AUTOMATIC
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DEADWRECKIN
  • MEMBER
  • 1 POST
The thermostat failed so I replaced it and the water pump while I was at it. Now when I start the truck in the morning the temperature gauge will slowly start to creep up over the C mark but short of operating temperature. Then it will drop all the way to the bottom of the dial, the heater will start blowing cold air and within a quarter mile the temperature gauge will spike all the way to overheat. Open the hood and the reservoir looks like it's boiling and hissing out of the cap.
I have found if I'm driving down the road I can put the truck in neutral, turn off the engine and let it coast for about a hundred yards start it back up and the temperature gauge will return to operating temperature and the heater will start working again, which will do me for a few miles and then it happens again. Usually about the time I get where I'm going it stops giving me problems.
I have since flushed the coolant system, removed the thermostat, tested it and replaced it again, and then tried to burp the system all to no avail. I don't appear to have a blown head gasket so I'm trying to figure out another way to burp the cooling system or if an air pocket is even the issue.
Dec 31, 2022 at 4:20 PM
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JACOBANDNICKOLAS
  • Experienced Mechanic
  • 110,240 POSTS
Hi,

What you are describing sounds like low coolant. When the engine is cold, have you confirmed the radiator is full in addition to the reservoir?

Also, when you first filled the system, when you started it, was the heater on high?

Let me know. Also, start the engine and before it starts to overheat, check the reservoir to see if there are any air bubbles in the coolant.

Let me know.

Joe

Jan 1, 2023 at 3:08 PM
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