Its Getting Hot in Here: The Temp Gauge EDITED 8/24!

I began the disassembly of the temp gauge earlier this week.  Something wretched happened to the face of the gauge at some point in its life.  I'm not so sure what I can do to save it.  Ultimately, the best solution would be to sand the face down and silk screen a new one across it.  I'm researching that option, but I am not so sure if I am capable of doing it...yet.  For now, I have resigned myself to trying to touch it up with modeling paint.  In hindsight, I should have left it well enough alone or shipped it to Stacy for the paint job.  Well, maybe someone can learn from my errors on the face restoration.

Untouched, cloudy and nasty.

With patience, a paint can opener and a flat headed screw driver, the bezel comes off.

The cloudiness of the glass was actually an improvement.

There were two tiny screws that mounted it to the canister. 
They were quite stubborn to relinquish their hold.

Cleaned-up and remounted to the canister.  A hack job at best. 
All that is left is to affix the bezel and glass.

I've been fretting over this darn temperature gauge for a bit over a week now.  I was finally able to source an appropriately sized piece of tube that has an inner diameter (ID) small enough to accommodate the small capillary tubes of the old and new temperature gauges.  At this time, I give the much deserved props to Robert, one of the plumbers we routinely hire for our property management business. 

 

"Buddy, you think the tube on a thermo-couple is small enough?" 

 

"What the hell is a thermo-couple?"  I ask. 

 

"Buddy, it doesn't matter.  Go pick one up at Lowes and check it out."

 

Well, how 'bout that.  It is PERFECT!  So, for $7.50, I bought a thermo-couple and chopped it up so I could use a 1" piece of its copper tubing.  By the way, I have several more inches left so I may try this again on my old, broken GPW gauge!

 

The theory is to remove the lower portion of the old capillary tube and mate the upper portion with the lower portion of the new tube.  To do this, the two cut ends will meet in the middle of a small tube which will act as a sleeve connecting the two.  The tricky part is that the sensing bulb contains ether gas, which travels through the tube and into the dashboard gauge which registers the engine coolant temperature.  If the tube gets cut, the ether gas escapes, rendering the gauge useless.  Also, it is VERY IMPORTANT to note that ether gas is HIGHLY FLAMMABLE!  To overcome this obstacle, it is a must to cut the tube without the gas escaping and then to solder (without flame) the edges of the sleeve airtight.

 

To begin the process, I picked a spot on my original, broken capillary tube to cut.  I went conservative in case my first attempt failed.  If I had been brave, I would have cut the tube closer to the gauge so the graft would be hidden behind the dash board.  I chickened-out mainly because I have ZERO confidence in my soldering abilities.  I'm pretty much historically O for 100 with successful solders.

Original capillary cut and a portion of copper tube is exposed to slide into the grafting sleeve.

The tip of the tube is cleaned AND I had to open the hole up since it was crushed during the cutting.

The new sensing bulb and the location where I cut the protective shield for the new capillary. 
At this point, I took the carnival inside to where I had my bucket of ice.

The sensing bulb is buried in a bucket of ice water. 
This "theoretically" ensures that the ether remains in the bulb while the tube is cut.

Before cutting the new tube, I soldered the sleeve onto the old line. 
To protect against solder creeping into the small hole in the capillary tube, I slid a small wire into the tube while soldering.

 Something of importance, at least for me. I practiced soldering another sleeve and a thick wire to see if I actually could make a good solder before attempting on the real deal.  Once satisfied, I moved up to the major leagues.  Also, I soldered the sleeve onto the old line BEFORE cutting the line with the new sensor bulb.  I figure the less time the ether can escape, the better.

The new capillary is securely soldered in the sleeve.

The video below is terrible.  I think I needed one more hand, but the kids were off playing so I didn't bother them.  However, I am pleased to report that the gauge works!  However, my only beef with this repair is that when I tested it in boiling water, the digital thermometer read 213 degrees F. while this gauge indicated about 195 degrees F.  Well, it is almost 70 and it barely needs to be recalibrated.  I think I will just keep the actual difference in my head while driving.   Now, if I can just figure out something to do with the face of the gauge.

 

The other project that I am currently stymied on is the speedometer gauge.  If anyone has a watch hand puller, can I borrow it?   See you next time!

EDITED 8/24/2012  New information added!

I could not stand how the face of the gauge looked so bad.  I have been contemplating other options (replacing the face, vinyl sticker with copy of face, silk screening, etc), but I just haven't found a solution that I felt I could do effectively as well as financially.  However, the other night as I was tidying up the garage, I found a second MB temperature gauge that needed the same repair.  Funny that I found it within minutes of getting my first one installed in the jeep!  That is how it goes.

The second gauge is from one of the boneyard jeeps.  This one has a great looking face, however, the protective glass is cracked across the middle.  I rummaged some more and located a bit more modern gauge (and when I say modern, I'm talking 1950s- its all comparative, right?) and this gauge appeared to have the right sized glass.  So, I did the ol' switch-a-roo.  Now the MB has a great face, great glass, and just needs a new bourbon tube!

I performed the surgury.  At first, I thought I had a bum gauge when the needle didn't move when I placed it in hot water.  I took it out and looked it over, stuck it back in and then it went!  It was 10 degrees lower at 150 degrees F.  By 180 degrees, it was within 5.  At 190, it was still within 5.  By 195 it was staying just short of the 190 mark on the gauge and it stopped moving.  No big deal, but just something to keep in my head when it is in the jeep and the engine is running.

Gauge reads 185ish, thermometer was 190.

By the time I focused, it crept up another degree.

On a side note, I found another supply of the copper tubing that is needed.  It was at the autoparts store in the gauge section.  Although I could have received a longer strand, it was $4.50 more than the thermocouple.

And as for the speedometer, I think for the current time, I am going to put a CJ model in while I disassemble my original Motometer.  I have made a friend in France who has had success rebuilding the speedos.  He is going to send me some pictures and instructions to help me with the restoration!