temperature sending unit

[tarps3]

Hi again.

I've got a strange question for you all.
I removed my temperature sending unit from my stock 352 Bird this weekend and, using a thermometer loaned to me by JohnG, I calibrated my stock temperature gauge.
That is, I immersed my sending unit in boiling water, connected it to the wire feed for the gauge and recorded where the gauge needle was at different points of heating/cooling. For instance, now I know that if the needled reaches the edge of the "P" in "TEMP", it is running at 200 degrees, the middle of the "M" is 180 degrees, and so on...

Anyway, before I did all of this, my needle ran in the middle of the "M" when the car was warmed up (according to the thermometer that should be about 180 degrees). After I wiped off the sending unit and installed it back in the block, my needle now runs on the right edge of the "M" in the space between the "M" and the "P" (about 190 degrees).

My question - did cleaning the sending unit (i.e. soaking it in boiling water) change the way it reads - is it more accurate now?
My opinion is that it had some build-up and was therefore reading incorrectly - now that it is clean, it registers the temperature more accurately.

Is this crazy? I checked my coolant level and everything is same as before - why would my needle read hotter than it did before I performed this test?

Also, if it is accurate, is 190 degrees too hot for this engine to run consistently?

Any ideas?

Casey
'60 hardtop

[Alexander]

RE: temperature sending unit

A coating of deposits on the temperate sensor may have insulated it.

Alexander
1959 Hardtop
1960 Golde Top

[tarps3]

RE: temperature sending unit

should I be worried if my car runs consistently between 185 and 190 degrees?

I knew I should have left well enough alone, but that John guy talked me into doing this!! ha!

Casey

[1960Bird]

RE: temperature sending unit

30 mph,60 mph or sitting still? Do you have air? Also what is your thermostat temp 160 180?

Steve Ronk
Cedar Rapids, Iowa
1960 HT 390, Edelbrock Performer RPM Intake, Shorty Headers, 2-1/2" Exhaust and 3.70 Rear Gears

[tarps3]

RE: temperature sending unit

When the car is warmed up and traveling at any speed, it runs at the 190 degree mark consistently. It doesn't "spike" when going from freeway to stop-n-go traffic, so that's good.
It was mild here this weekend (mid 70's to 80's) and I drove her on the interstate as well as in traffic - day and night conditions.

I don't have A/C.

I do have a 180-degree Tstat.

Casey
'60 hardtop

[Alexander]

RE: temperature sending unit

>should I be worried if my car runs consistently between 185
>and 190 degrees?

No, that is normal.

Alexander
1959 Hardtop
1960 Golde Top

[1960Bird]

RE: temperature sending unit

I agree, that seems a bit warm. In 75-80 degree temps sitting at a Stop light I will get to about 190 degrees, If I sit there a long time it may go over 200. Going 30-50 MPH I will run about 180 to 185 or so. What is odd, is that your temp doesn't climb when sitting. I think that I would check your radiator. Also remember that your transmission fluid is being cooled by your radiator and at 190 or so all the time you do not have much cooling capacity for your transmission...JMO

Steve Ronk
Cedar Rapids, Iowa
1960 HT 390, Edelbrock Performer RPM Intake, Shorty Headers, 2-1/2" Exhaust and 3.70 Rear Gears

[Guest]

RE: temperature sending unit

A few thoughts

You may want to review grounding on your sensor. If the resistance in the circuit changed from when you had the sensor out for calibration and then reinstalled it, it would affect the position of the needle (a better connection - less resistance - would increase the temp gauge reading). Possibly there was corrosion at the sending unit ground that was eliminated when re-installing.

Not sure how accurate these things might have been in the first place, particularlly compared to today's digital instruments. I would think of them more of a rough magnitude indicator - whether the engine is to cold to operate the t'stat or if it's about to boil over....

[tarps3]

RE: temperature sending unit

I think I've got it now!

A short synopsis on what has been done to my cooling system in the past year:
rebuilt/repaired radiator
new expansion tank
new hoses
new thermostat
flushed system and new coolant

I haven't replaced the water pump as it has been fine.

Anyway, I read in the shop manual that the exhaust gas valve which is in the passenger side exhaust manifold can cause the car to run hot if it isn't operating properly. Having checked everything else (including the feed wire to the sensor and making sure the grounding is adequate), I checked the exhaust gas valve.
Wouldn't you know it, the little coiled spring had unhooked itself from the little "pin" and the valve was staying closed.
I slipped it back on the pin, lubed it, and drove the car after work for quite aways. It got up into the upper 80's yesterday (this weekend it was in the low 70's) so I figured if it was gonna run hot like it was, it would sure do it yesterday.

The temp gauge never even got to the right side of the "M" - Saturday it ran between the "M" and the "P". I drove it on the highway, in traffic (it spiked a little at the stop lights) and let it idle. It ran consistently between 180 and 190 degrees.

I never would have thought the gas valve could make such a difference, but it's always the little things that get ya!

thanks to everyone for their help!

Casey
60 hardtop

[Thunderhans]

RE: temperature sending unit

For general info, to get collected moisture (e.g. condensate)out of the engine oil the oil every ones in a while needs to heat up to above water boiling temperature; above 100 degrees Centigrade. If I'm correct that's 212 degrees Fahrenheit.

How high the cooling fluid temperature will rise is depending on the temperature rise and drop in the cooling system.

I know that the oil in my motorcycle can easily reach a temperature of 270 degrees F.

Hans
1959 Hardtop
430 ci