Ford Inline 6 Cooling Problem?

I've got a 1980 Ford F-100 I bought new in 1980 with an inline 6 and no A/C. It has always run in the "normal" temperature range until recently when it started running right on the "cold" line of the gauge. I thought it was the thermostat, so I replaced that. Now, when it's cold and I start it up it rises to the beginning of the "normal" range or even a little within it, then it drops back to the "cold" mark and just stays there.

Any ideas abt what's wrong? Will it hurt it to drive it like this?

Thanks,

Fred

Reply to
Fred
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Does the radiator hose feel hot to the touch? If so, it's probably a problem with the sending unit on the gauge. I the problem was running too hot then I'd say replacing the thermostat wouldn't fix it but with a new one, I'd bet it running at the normal temp and you just don't know it is.

Tony

Reply to
Anthony

The problem can be one of three things: sending unit faulty>instrument voltage regulator faulty>open circuit in the system. Here are some tests:

Put a thermometer in the neck of the radiator and let the engine run. When the thermometer reads 180=B0, the gauge should read in the Normal range. If it doesn't>disconnect the gauge lead from the sending unit and connect a 12v test light/VOM(+ lead) and the (-lead) to engine ground. Ign key ON>the test light should flash or the VOM should read a fluctuating voltage which indicates the instrument voltage regulator is operating and the circuit isn't grounded. If the test light stays on or the voltage reading is steady, the instrument voltage reg is bad. No light/no voltage means the circuit is open. If all the readings check out correctly but the gauge doesn't read properly, replace the sending unit.

The sending unit is a resistor. It restricts the flow of current depending on the temp of the coolant. Low coolant temp means high resistance and short movement of the gauge indicator.

I had the same problem with my truck ('81F100IL'6') so I installed both an oil pressure gauge and water temp gauge set.....about 20yrs ago and have never looked back.

The IVR is located behind the instrument cluster....loads of fun to get to, since you must pull the instrument panel and the cluster assembly.

Hope this helps

Dave S(Texas)

Reply to
putt

The problem can be one of three things: sending unit faulty>instrument voltage regulator faulty>open circuit in the system. Here are some tests:

Put a thermometer in the neck of the radiator and let the engine run. When the thermometer reads 180°, the gauge should read in the Normal range. If it doesn't>disconnect the gauge lead from the sending unit and connect a 12v test light/VOM(+ lead) and the (-lead) to engine ground. Ign key ON>the test light should flash or the VOM should read a fluctuating voltage which indicates the instrument voltage regulator is operating and the circuit isn't grounded. If the test light stays on or the voltage reading is steady, the instrument voltage reg is bad. No light/no voltage means the circuit is open. If all the readings check out correctly but the gauge doesn't read properly, replace the sending unit.

The sending unit is a resistor. It restricts the flow of current depending on the temp of the coolant. Low coolant temp means high resistance and short movement of the gauge indicator.

I had the same problem with my truck ('81F100IL'6') so I installed both an oil pressure gauge and water temp gauge set.....about 20yrs ago and have never looked back.

The IVR is located behind the instrument cluster....loads of fun to get to, since you must pull the instrument panel and the cluster assembly.

Hope this helps

Dave S(Texas)

Reply to
Anonymous

I think you have some air in the cooling system, or you bought a thermostat without the small bypass notch or hole. Look at the old thermostat to see what I mean. Look at the part that opens and you should see a small hole or notch to allow air to get around the closed thermostat.

Al

Reply to
Big Al

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