740 is to hot any ideas why

sqbrick · Post by **sqbrick** » 04 Sep 2010, 05:37

I just bought this 1992 745 w/172000 mi. on it. All is great other then it runs really hot. The temp. gauge shows it at the half way mark but it can't be right.The engine gets so hot nothing under the hood/bonnet can be touched other then the air intake and batt.Even the outside of the fender/wing gets really warm. How would I test to see if my temp. gauge works right? And what could be causing it to get so hot? (water pump?) Any info would be great Thanks.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 04 Sep 2010, 07:10

sqbrick wrote:I just bought this 1992 745 w/172000 mi. on it. All is great other then it runs really hot. The temp. gauge shows it at the half way mark but it can't be right.The engine gets so hot nothing under the hood/bonnet can be touched other then the air intake and batt.Even the outside of the fender/wing gets really warm. How would I test to see if my temp. gauge works right? And what could be causing it to get so hot? (water pump?) Any info would be great Thanks.

If it is not boiling over and spilling coolant on the ground, there may be nothing wrong...The cooling system is pressurized and will be normally about 230 degrees...A thermometer inserted into the overflow tank will not give the true temperature because it is off to the side and several degrees cooler than the engine is...Be careful removing the overflow tank cap when the engine is hot, you could get scalded because the system is under pressure...

Besides the conventional engine driven fan on the water pump there is an electric fan in front of the radiator that should come on when the engine gets hot...It is controlled by a temperature switch that is mounted in the back side of the radiator tank on the right side...It might be near the top or it might be down in the middle of the tank, but it has two wires coming off it...Wiggle the wires part way off so that metal terminals are exposed and while the engine is running short those two terminals together with a small screw driver...The fan should run...If it does, that switch is suspect, if it doesn't, there may be other problems...The fan can be seen by removing the grill, which is held in place be two pinch-clips inserted through the hood striker plate...

Volvofix1 · Post by **Volvofix1** » 11 Sep 2010, 08:43

This is how to check temperatures...go to an auto parts store and buy a non contact scanning thermometer, they now cost about $30 the ones we use in our shop had cost $125 to $150 but it was a tool we needed. We use them to check temps of engines,brakes ,tires,cat. converters and radiators. Buy one and hold it near the thermostat housing, radiator and radiator hoses to take and compare readings, this is an excellent diagnostic tool and the best way to verify temperatures. For example scan the radiator hose going into the radiator and check the temp. on the other hose you will see a difference in the readings.At our shop we test,measure and research when diagnosing a problem to make certain what we tell the customer is accurate and correct and give a proper repair estimate. Pep Boys,Autozone and other chain auto stores now carry them so you can now calculate how hot is hot...sounds like that Soca song Buster Poindexter used to sing.

Dick K. in Fla.where it is hot hot hot !

Retired MVS Contributor · Post by **Retired MVS Contributor** » 11 Sep 2010, 09:07

The best tool in the world for A/C analysis, evaporator input and output temps can be compared...

JimG63 · Post by **JimG63** » 13 Sep 2010, 07:31

Never hurts to flush the radiator and put in a new thermostat. New radiator is only $115 at Napa too. Now I know what the sensor that I forgot to swap out yesterday does.