I have 1997 , 4cyl, 5 speed, Ranger. Recent purchase. Everything working just fine, had great heating and defrost. We are expecting very cold temps, so I checked radiator fluids, was brown and some debris noted in radiator. took truck to mechanic for flush and fill. He said it was very dirty ( I knew that ). He did flush and changed the thermostat. I had heat for about 10 minutes after getting truck back. Now no heat. Temp gauge stays pegged on cold when heat is off. When heat is turned on, the temp gauge moves up off the C, but not into a normal range, but blows cold. Could heater core be plugged with debris from the flush ? It had been working just fine till it was messed with. replies greatly appreciated.

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1997 BLUE/GREEN 5 SPEED 4CYL RANGER

After the truck has ran for a bit can you check the two hoses that go into the firewall. They should both be hot if it’s circulating through the heater core properly. If they are not the same temp then the the heater core is clogged. You can use a laser temp gauge to check the hoses.


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2002 Ford Ranger XLT 4x4, ext. cab, Stepside, Auto, 4.0L v6

Sounds like the thermostat is stuck open.

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I would look for the cooling system having some air entrapped.

Run the engine and feel the upper radiator hose. It should stay cool, and not warm slowly. Once the coolant in the cylinder head reaches temperature, the thermostat should open and allow flow of hot coolant. Not before.
If it warms slowly, or not at all, your thermostat is likely not working.
Squeeze the upper hose with the engine cold, and listen for bubbles or sloshing. If you get that, your coolant level is a bit low.
tom