I have a 1992 Ford Tempo, 85,000 miles. It has a 3.0, V6, automatic
transmission. The problem is that when I'm sitting at an idle, the
temperature gauge reads quite high, around the A or L in NORMAL. If I
rev the engine, it will fall back down to the O or R range. Of
course, if the fan comes on the engine will cool a bit, but not where
I'd like it. There is plenty of coolant in the system and the
thermostat appears to be working. The heat in the car works fine.
There is no coolant in the oil and I'm not losing any; the system
remains full. Any ideas? Thanks.
It sounds like you don't have a serious problem. The gauge is not
calibrated, so it is difficult to use it's position to determine if you
have a real problem. I suggest that you take the car to a shop that can
measure the actual radiator temperature (most use a infrared thermometer
these days, it only takes a few seconds). You might also check the
operation of your cooling fan. I don't know about your Tempo, but my old
Sable with the 3.0 had a two speed cooling fan. The low speed engaged
often when you were idling. The high speed only engaged when the car got
near the upper end of the acceptable temperature range. It is possible
that your low speed is not working properly, so the cooling fan only
engages on high speed when the car is near the upper end of the acceptable
range. Without the electric cooling fan, the car will tend to run hot at
an idle, since there is nothing to move air through the radiator. One more
thing, make sure there is no air in your cooling system.
I think he's right and you don't have a serious problem, but I don't think
it's mechanical and my first action wouldn't be to check rad temp or fan.
First I would check grounds on the engine block and the battery, if you have
a multimeter I would test impedance to make sure you have a good ground.
Next I would look for wires coming off the temperature sensor and make sure
they're not close to anything that could throw off EMI. This could be any
electrical component but especially spark plugs, wires, distributer, and
alternator. You could try try putting sheilding around these wires as well,
or even go to radio shack and get a noise filter. I think your problem is
similar to whines heard in the radio that increase with RPM, which is EMI
from your ignition system.
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