Coolant temp measurements

[Bmachine]

After emptying, refilling and then bleeding my cooling system, I noticed that my temp gauge reads lower than before. It used to stay around 4 o’clock but now it is staying steady around 5. Just above the blue. When climbing a hill it goes “up to” 4. The ambient temp is low 40s (mid 10s C) but the Tstat should still be keeping the motor in its proper operating temp. There is plenty of coolant in the overflow tank, no visible leaks, top radiator hose is hot, bottom a bit cooler so nothing obviously wrong. So I’m wondering if the temp sensor or even gauge may be off.
So I was wondering if there was a set of ideal temp numbers that can be read with an infrared gauge at a few critical points. I’m thinking about:
- Overflow tank
- Top of radiator (on the metal, not the hose)
- Bottom of radiator
- Front and then back of Tstat housing
- Both heater hoses at the firewall.

 

[Mike Goble]

That's why I run a mechanical direct-reading gauge in my Bavarious. It reads the temperature in the thermostat housing, and it varies somewhat depending on weather, incline, speed, gear selection, coolant mixture, etc. The only real change in temperature you will be able to measure, and the only one that really matters, is the drop across the radiator. Here is some good information on cooling systems:

Engine Cooling | Coolant Performance | Radiator Additive

An article on Engine cooling mods with how to improvements to get better cooling for your motor with lower coolant temps and better heat control on the track

www.enginebasics.com

 

[Stevehose]

Based on the chilly temp, your gauge reading seems ok to me, will go higher in hot weather.

 

[Bmachine]

Based on the chilly temp, your gauge reading seems ok to me, will go higher in hot weather.

At first, I thought so too. But isn't the role of the thermostat and fan clutch to keep engine temp more or less the same, regardless of outside temp? At least at idle.
Obviously, in extreme weather and under load this will vary quite a bit.

 

[Bmachine]

That's why I run a mechanical direct-reading gauge in my Bavarious. It reads the temperature in the thermostat housing, and it varies somewhat depending on weather, incline, speed, gear selection, coolant mixture, etc. The only real change in temperature you will be able to measure, and the only one that really matters, is the drop across the radiator. Here is some good information on cooling systems:

Engine Cooling | Coolant Performance | Radiator Additive

An article on Engine cooling mods with how to improvements to get better cooling for your motor with lower coolant temps and better heat control on the track

www.enginebasics.com

Interesting read. 10 degrees F is all you can expect as a drop from top to bottom of radiator. I would have thought it was a fair bit more than that.

 

[HB Chris]

At first, I thought so too. But isn't the role of the thermostat and fan clutch to keep engine temp more or less the same, regardless of outside temp? At least at idle.
Obviously, in extreme weather and under load this will vary quite a bit.

These are analog style systems, you can't expect modern digital accuracy. Mine stays at 4:00 with the b35 and will read 5:00 in early morning if very cold.

 

[Bmachine]

Interesting. So maybe my gauge is correct after all.

 

[Mike Goble]

Interesting read. 10 degrees F is all you can expect as a drop from top to bottom of radiator. I would have thought it was a fair bit more than that.

Think of the radiator as a heat exchanger, not a water cooler. The rate of heat exchange is determined by the average radiator temperature, so the more uniformly hot you can make the radiator, the more heat it will dissipate. If you lower the outlet temperature by 10°, you will need to raise the inlet temperature by 10° to keep the same rate of exchange.