Heat gauge indicates high.

[Guest 5Wbob]

The heat gauge of my 1950 Dodge Diplomat w/ a 230ci engine indicates a top of scale.

When I shoot the engine with the heat gun, I get acceptable (180-185F) readings on either side of the thermostat housing and on the cylinder head and around the heat gauge sender. 

Could this possible be some type of failure of the distribution tube.

On a cool day, the heat gauge reads about 165F which is the thermostat setting so I do not think it is a gauge problem. 

The car runs fine and does not boil over.  I am running a 4# pressure cap.

 

Thanks for any help.

 

5wbob

[hchris]

Based on your heat gun it would seem likely the guage or sender unit is at fault, the indication error is not necessarily linear so you may be indicating correctly in the lower ranges but out in the upper reading.

 

A more positive gun reading would be at the radiator inlet elbow verses the outlet elbow, a good radiator should produce a 10 to 15°C temp drop between inlet and outlet.

 

Aiming your gun at the front then back of the block, where the distribution tube is located, should give you some idea of localised temp differences.

 

Lastly you could always remove the rad cap and insert an industrial thermometer, whilst bringing the engine up to temp, and make comparisons with your guage.

[Guest 5Wbob]

Thank You

 

I appreciate your answer

 

Bob