Datsun Roadster Forum-311s.org

Question for those smarter than I ....everybody !! I’ve changed out my radiator, filled it. No leaks, but the temp gauge is somewhat erratic. Doesn’t ever go past the second line on the gauge. Anyone know what that line represents ? 1970 SRL 311. At what I think is operating temperature, I get 60 ohms across temp sensor to ground. Also is there a way to test whether the water pump isn’t moving enough water through the engine ? Fan doesn’t wiggle, there is no excessive noise or drips from it.

Ground the temp guage wire the guage should peg
And pull the thermostat to see if the impeller seperated off the pump
Best to point the front of car up hill and fill the radiator over the opening with a funnel.

Grounding the wire does in fact peg the gauge. Not understanding your suggestion of pulling the thermostat to see if impeller is separated off the pump ? I'm not running a thermostat anyway

If the impeller separates from the water pump shaft, you have no forced circulation.

My experience is the brass thermosensors suffer corrosion, internal, as well as in the aluminum housing, and fail to deliver a signal.

My 69 2000 hardly moves the gauge either. On a very hot day it might reach the little f mark. I have heard that the f represents apx 190* which is about what the engine should run at. I have used an infrared thermometer to check the temps around the cooling system after driving 30 minutes or so and with the needle at only the second mark I was only seeing 160 to 170 degrees. You should check yours to to satisfy yourself that your engine is operating safely.

You can see it cold that way ...also feel the hoses if it's flowing it will be hot

jayedeluxe wrote: Tue Jun 29, 2021 2:27 pmI'm not running a thermostat anyway

Probably your issue is right there , the job of the thermostat is to regulate the engine temperature so that it runs in its optimal range
By having no thermostat the coolant circulation is opened 100% of the time making the car run colder than optimal which hurst , mileage power and durability

My 2L runs right around the "F" mark as well. I look at the temp gauge as more of a relative than an absolute measurement (precision vs. accuracy I guess). One of the thing I love about driving the roadster is that when you drive through a cool patch of air you feel it. Then you look down at the gauge half a minute later and the gauge reflects the temp drop. Adds to the raw, visceral experience of driving.