1947 1/2 ton - 216. Can't seem to find info about the problem I have with my temperature gauge. (I hope this is the right forum as the gauge is mechanical rather than electric. Engine forum?) When cold, the temp gauge reads 180. The gauge goes to 212 when the truck warms up. At operating range, an infrared thermometer pointed at various places on the engine gives a reading of 180. Is there a way to 'center' the gauge so it reads 100 when cold? Thanks in advance.
It's a small world, but I wouldn't want to paint it.
A typical pressure gauge is activated by a bourdon tube. The temperature gauge is a pressure gauge operated by the bulb with a gas inside the pushes on the tube inside the gauge itself. There's a linkage inside that probably has a gear involved and it may have slipped a tooth or three. You might be able to fix it, but you're probably better off finding a replacement. Here's a video that show how a typical pressure gauge works. www.youtube.com/watch?v=9avIVZP1Ka4 The first part of the video is probably similar to your temperature gauge.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Rusty years ago there were people who repaired these gauges all over the place, but today I'm not certain. To "center" the gauge may be difficult as there is a square cutout that orients the gauge within the instrument cluster. If you have a Dremel moto-tool and a metal cutting bit, you might be able to re-cut that square or do away with it and then re-drill the 2 screw holes but it won't be easy work at all...something to take up time on a cold wet night, possibly. As I recall there are not really teeth in there. I think the tube terminates in a copper circular affair which then connects to the needle. There is one other possibility...maybe a stretch but definitely the kind of thing I'd consider trying. See if you can move the needle back to 100 when the truck is cold. Your gauge is working...sort of, so it means maybe the needle got bent somehow. Good luck!
Last edited by Jon G; 09/25/20231:18 PM.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
As it is now, it's not accurate, so pull it out and bend the small arm that attaches the needle to the pressure tube. They are adjustable, it would have be too difficult to build them all 100% correct the first time out. As the pressure in the tube expands from heated fluid, it pulls the needle. Was it ever accurate? Has something changed? https://www.bowtiebits.com/index.cfm used to repair them, they extended mine 20 years ago.
Remove the gauge sensor bulb from the engine, and take the gauge out of the dash. Immerse the sensing bulb in a pot of boiling water and adjust the needle position to 212 by whatever means necessary- - - -bend linkage, change gear position, etc. The boiling point is the important indicator. Let the "cold" setting fall wherever it chooses- - - -you want to get an accurate "overheat" reading to protect the engine. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
If you are using Jerry's method of calibration and can borrow your wife's cooking thermometer without her knowing, let the boiling water cool down to 180 as indicated by the wife's thermometer and note what your temp gauge reads just for future reference.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
To "center" the gauge may be difficult as there is a square cutout that orients the gauge within the instrument cluster. If you have a Dremel moto-tool and a metal cutting bit, you might be able to re-cut that square or do away with it and then re-drill the 2 screw holes but it won't be easy work at all...something to take up time on a cold wet night, possibly.
Jon, It really won't work to reorient that square hole as the needle and number scale are in one assembly. It would just reorient the whole gauge behind the bezel. You may be right about there not being any gears in it as it's a partial sweep needle and might just have a link between the bourdon tube and the needle lever. I haven't looked at mine for a few years. Here's a picture of the gauge and it's mount in the cluster.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Ah, you're exactly correct, Kevin. Sorry...forgot about that. So my idea of bending the needle/needle down piece is probably what must happen along with setting the temperature as Jerry mentioned. I'm nearly certain there are no gears...just the tube connecting to the C shaped affair's end. Unfortunately I don't have an image of the back side of it or I could say with certainty. Thanks!
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
