Masfel74

bfit

I would lean towards 185F
you should have a probe in the outlet to top of radiator, that will give you a reliable temp to work off.
there will be areas in the engine hotter , but you need a mean temp that is repeatable to test .
radiator efficiency is measured across the core in this case top to bottom usually a minimum of 12 degs C, on a hot day
bfit

MelWff

I put my money on the temperature sensor causing the 210 reading on the gauge.
Why did you change it and can you reinstall the previous one?
If you dont have the old one try one in the link below
https://www.lectriclimited.com/tempe...ng-unit-108485

Bikespace

I'd shoot the upper radiator hose (warm engine) with the IR gun and trust that. That should match your gauge reading, or the gauge is off.

Can you check your IR gun?

Masfel74

The previous one was broken. I bought 2 new sending unit, different brands, same result.

Masfel74

I checked with IR gun. The temperature in the upper radiator is around 210 so the sending unit seems ok, But why I read 185 in the water in the expansion tank?

7T1vette

Best place to measure coolant temp is at the outlet housing containing the thermostat. If yours is chrome, shiny or dirty, the IR reader may not be accurate.

Boil some water on your stove. Then turn off the burner and use the IR reader to measure the side of the pan. It should be close to 210*F. If so, the temp it measures at the water outlet housing is what I would go with.

In general, the temp sending units are a POS, when it comes to being consistent or measuring with any reasonable level of accuracy. Even with a good one, you should not expect it to be any better than +/- 10*F of actual temperature {in the cylinder head}.

REELAV8R

An IR gun likes a flat non-reflective surface. I would take the temp on the hose just after the thermostat. That should give you the most accurate reading.

using a 160 thermostat will not lower your running temps. Only a more efficient radiator and/ or more air moving through the radiator will do that. At least on the cooling side of the equation. Tuning is the other side, ie more timing , proper fuel mixture etc.

Masfel74

Yes I',m agrre; in fact my doubt is about the thermostat, I sospect that it opens too late...

Bikespace

I'm not sure how a 69's expansion tank works. Is there constant flow through it, or only partial flow? Is there air volume? In my later cars, the expansion tank only sees flow in and out through one hose, so it would be expected to be much cooler. We also have a radiator cap, which is nice. The upper hose (for reasons pointed out), is your best bet, as there should be water flowing through it at all times. If that's reading 210, that's probably what is going on. But why?

When are you taking the readings? I measured several temperatures in the engine compartment of my 79 with some thermocouples (including the upper radiator hose). The steady state reading was right at 180 (matching the thermostat) on a hot day, but it spiked over 210 when parked for just a few minutes (engine off).

Rescue Rogers

Buy one of Willcox's adjustable resistors for the temp gauge. You can adjust the gauge to read what the IR Thermometer is telling you. The sensor should be consistent so the error would be linear, thus being corrected to actual temp at one reading should be reflective of the readings across the spectrum
I would go with rhe temp of the upper hose as the iron block will be radiating cylinder heat so the metal temp will be different from the coolant temperature. The rubber hose wont conduct the metal housing temp so it should be close to the actual water temp. As for the coolant tank, my 68 tank is off to the side and acts as the radiator fill. Also it would be loosing heat as the fjuid moves though the hoses so I wouldnt go by that.

v2racing

Temperatures are really dependant on where they are taken. Temp sensors in the head will read higher than temp sensors in the top of intake or thermostat housing. My Vette after driving a couple hours of mixed city/highway driving on a 95 degree day was reading 210 on the dash gauge. I took temps with an IR gun with the car still running. At the temp sensor in the left head it read 210 degrees, same as the dash gauge. At the thermostat housing it read 165, I have a 160 thermostat. At the center of the radiator it read 140.

Automakers put the temp sensor in the heads because that is the critical place for temps for emissions, unlike in earlier years when that was not an issue.

Before someone asks why I run a 160 degree thermostat, it's because this engine has almost 12 to 1 compression. Lower engine temps make the engine less sensitive to detonation and will make more power. I have a cooling system capable of keeping the coolant at close to the thermostat temp. Win, win!

Mike.

Masfel74

Thanks everyone for the answers.
Cause the IR doesn't read good the rubber of the upper hose (also modifying the wavelenght) I put the probe thermometer on it.

Running in this way, after a long time the temperature I read (engine on) is around 170 °F...


So, finally:
temp gauge: 210
IR on pump: 230
probe thermometer in the tank water: 185
probe thermometer on the upper hose: 170
...

Street Rat

I have an Autometer electric water temperature gauge. The sending unit is in the cylinder head. It seems to hit 210 frequently. I've got an awesome cooling system. I don't understand why the engine is running this warm. I'm not running a high compression radical motor by any means.

Craig

v2racing

Head temps are always going to read higher than the coolant exiting the engine. Look how close the temp sensor is to the exhaust ports. Lot of heat in that area. Move your sensor up to the thermostat area, you more than likely would see lower temps.

Mike

ronarndt

"Head temps are always going to read higher than the coolant exiting the engine. Look how close the temp sensor is to the exhaust ports. Lot of heat in that area. Move your sensor up to the thermostat area, you more than likely would see lower temps.

Mike"
I did this on my 68 convert with NOM 454 and it changed the temp at highway speed from over 210 to 180

Street Rat

I have moved my coolant sensor all over. The cylinder head is the hottest readings that I have gotten. I'd prefer to know that the reading that I have is the hottest that the coolant is actually getting .. I've put an IR gun on it and the gauge is accurate. The headers are extremely close yes. They may be contributing to a higher reading at the coolant sensor. How about a spark plug sleeve over the sending unit? Think I'll try that. Thanks for the response v2racing. Your posts are always spot on.

Craig


.

Masfel74

Thank you to everyone for the answers.
So at least it seems that everything is ok like this