VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1930 Temperature Sensor/Gauge

i noticed that when i did get the truck running that the gauge never moved. even when it was running hot.

is there a way to test the gauge and validate it works ?? how does it function/work, only using the tube or does it require power ??

it is screws into an adapter/bushing, then adapter/bushing to the block. assume if i unscrew it then coolant will pour out until level drops below the open port ? or is it in a sleeve of sorts ??

Assuming that it is the same a my '31, no power is needed. The tube is filled with ether (I think) which expands as the temp rises thereby moving the gauge.

A simple test is to remove the sending unit from the cylinder head and put it in water. Heat the water and the gauge should move.

Somewhere on the forum are instructions for rebuilding the unit, but it's not easy.

Be sure to drain the radiator before you remove the bulb from the head, or you'll have a lot of antifreeze all over the place!

All the Best, Chip

that is what i was wondering... so it is an open port !!

hoping to get it fired up today for a quick trip around block for test and tune...

Yes it is a port that exposes the bulb directly to the coolant.

is it all one piece gauge & sender or are they 2 separate pieces ??

wondering if i could test to see if gauge was bad or if sender was bad or if one one unit i guess test as above and if does not work unit is bad as a whole

ok looks to be one piece unit, that goes into the dash. does not look like the tube comes off ?!?

A mechanical temperature gauge is a sealed unit. The sensing bulb is connect to the internal gauge mechanism by a thin somewhat flexible tube. It is filled with alcohol that vaporizes and increases the pressure within the sealed system as the temperature rises. That increased pressure moves the needle.

Be very careful handling the whole assembly. If the tube is crimped or fractured the system will no longer work. Sometimes they can be repaired but at a price.

gonna remove the unit and validate if it is working, but seems it is not, as the water pump is pumping water nicely and the engine is getting warm, using a temp gun getting temps around 180 on the cylinder walls, radiator is 160 at teh top to 140 at the bottom, and gauge is not moving.

what are options for replacement or rebuilding ??

well just dropped off my temperature unit to go to Roy up in Vermont. should be there Thursday :)

also called a few other places, seems there are several places that rebuild these vintage sealed systems. everyone that i talked to seemed to know what they were talking about and how to repair/service them. it is good to know there are options out there. some of these places can also do a complete restore on most gauges, backgrounds, faces, needles, etc.

thought i would post a few pictures of the gauge assembly when i removed it.

few picts of the test i ran, boiled some water in a small bowl, and then dropped in my thermometer to see what the temperature was, and then dropped in the bulb from the temperature unit. the temperature unit did not budge or move. water was at 200F so figured it would at least get to alcohol boils since that is around 170-180F

got my temperature gauge back today from Roy M

going to do a control test to see what temperatures are where on the gauge for my reference.

he put on a a new capsule & tubing.

in case anyone is interested or needs some work done, here is his card & information, he only does mechanical temperature gauges, NO electronic of any type.

Roy Martin
The Temperature Gauge Guy
(802) 862-6374

well did a control test with water and a thermometer

so i know where the engine should be running and staying.   if it gets near HOT they we are at 200F !!

considering these engines run bt 140-160 it looks like the gauge should be around alcohol boils or straight up.  granted alcohol boils is around 171F. 

Methyl alcohol boils at 148.5 deg. F. That is the alcohol they primarily used in the 1930s and that is the point identified on the gauge. Ethanol that boils at 173.1 deg F. Depending on the concentration in water the boiling point will change a little for both alcohols.

Thanks for the update on Roy's. It's good to hear he's still repairing these gauges. That's a pretty fast turnaround considering everything going on today.

Thanks Chipper for the clarification, makes sense :)

main goal of my testing was to know a general temperature based on where the needle is pointing on the gauge. this way i can monitor the temperature of the coolant more accurately. and based on your information, that would make the gauge pretty accurate !!

yes it is, plus the other few shops i found that do it.

Roy says work is pretty steady, but is pretty caught up

his charges are very reasonable as well

thought i would share some photos of the temperature gauge assembly and the install

looking very nice keep it up!!!

Great repair job,but keep in mind the sensor bulb is at the rear of the cylinder head(the hottest part of the cooling system)and it's sitting so close to No.6 exhaust port,not a brilliant design feature,it's bound to show a higher reading than normal.