Wednesday, November 22, 2006

AV - More VW Oil Temps

> My oil temp sender is in the case at the back on the left hand side. I've insulated it and installed a blast shield, as the temp's never seemed to come up. >


You're probably reading the temperature of the crankcase rather than of the oil it contains. (Easy to check. Use an IR-type thermometer.)

Volkswagen installed full instrumentation on some of their industrial engines. The oil temperature sensor was installed in the opening immediately adjacent to the right-hand side of the oil pump (when facing the pulley). The tip of the sensor was in the flow of oil entering the pump.

Oil temperature within a Volkswagen engine may vary by up to 200 degrees, depending on where the temperature is taken. The hottest oil is in the vicinity of the exhaust valves. Oil adjacent to the walls of the sump tends to be the coolest due to the partitions cast into the case under the cam-follower bores, breaking the sump into a series of stall-like compartments in which the oil does not circulate. In placing the temp sensor at the inlet to the pump, Volkswagen was trying to measure what they called the 'core' temperature of the oil.

Another temp-sensing location to avoid is the sump plate. The popular VDO sensor that replaces the drain plug typically reads about 100 degrees Fahrenheit less than the oil measured at the inlet to the pump.



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