How about sorting out the sheep from the goats? Gawd I'm getting to sound like an old guy! Although you could have an underperforming cooling system, the indication the gauge is giving you might be traceable to a fault with either the gauge itself or the coolant temperature sensor.

The "green book" lays out a simple test procedures for these items.

1. Disconnect the wire at the sensor. The sensor is located in the side of the engine block below the intake manifold.

2. Connect the wire in series with a 68 ohm resistor to the negative battery terminal. I couldn't find a resistor with that value, so I connected two resistors inline that added up to the 68 ohms

3. Switch on the ignition. The gauge should indicate 3/4 of the way up the scale with a tolerance of +/- one needle width.

If the reading is incorrect, the gauge is faulty.

If the reading is correct, the sensor is faulty.

You can test the sensor itself with a VOM and thermometer and hot water. The values given for the pre-87 single wire sensor are:

140 deg. Fahrenheit = 217ohms +/- 35 degrees
194 deg. Fahrenheit = 87ohms +/- 15 degrees
212 deg. Fahrenheit = 67ohms +/- 11 degrees

The "green book" also has the values for the two-wire '87 and later sensor.

Another possible contributing factor might be a poor connection at the sensor due to corrosion. You'll probably correct this condition just by disconnecting and reconnecting the wire.

You can make things a bit more comfortable when removing and replacing the sensor. Pop the distributor cap and place some rags over the distributor. This allows you to slide your arm and hand right in there.

By the way, a similar procedure may be used to check the fuel gauge.

You would be correct in assuming I'm a "piston farmer" (only recently learned this equivalent for "gear head"). I have actually done this kind of stuff for fun.

Regards,

Tatra Mike
Seattle, Washington

1985 244 "Alfsen" (wife's car - the good one)
1984 245 "Buster" (the kid's car, now sold)
1985 245 "Cosmo" (parts car, sold off for move to WA)
1985 245 "Daisy" (back seat down, full of tools, the work truck)
1985 245 "Earl (CA vehicle 'retirement' program)
1985 244 "Junker 1" (Bought for parts, currently being dismantled)

Can you tell I prefer the 1985 model 240? Better headlights than the plastic 1986+ and nicer belt adjustments than the 1984s and earlier!