Need help with capillary tube replacement on Stewart Warner water temp gauge

Hello people of superior knowledge. I need help/ideas/comments on capillary tube replacement for a bourdon tube style mechanical temperature gauge. I got a little carried away over the past few years collecting Stewart Warner greenlines and big block logo gauges, and a few of the water temperature gauges have the sending unit (capillary tube) cut off the back of the gauge. I figured I should try to repair them in the event I want to use them later on or sell them off and wonder why I decided to buy so many of them in the first place!

I have tried the repair procedure outlined in the below link several different times with about the same result each time, that being a mundane and marginal success. (Note: this is discussed on the HAMB several times, with each thread linking this site below, so I've used the search function in hopes of finding my answer before posting.)

http://www.ply33.com/repair/tempgauge

Before I tried doing this, I checked the donor gauge using a pot of increasingly hot to eventually boiling water and a Craftsman digital multi-meter that has a temperature function. The donor gauge checks out on calibration each time (checking from 160*F - 212*F), so I submerge the bulb in a salt/ice water bath (measured at 29*F - 34*F) and begin the prep of the old gauge, copper tube sleeve, shrink wrap, trimming the protective rubber off the tube of the new gauge, etc.

After the prep work, I began by soldering the sleeve onto the back of the gauge needing repaired (using a soldering iron for the entire procedure-no torches). I found out the hard way I needed to check the gauge at this point to ensure I hadn't soldered the tube shut! Just for your information, it was super fun melting/drilling the solder out of that tiny tube. Super fun. Another FYI: if you need to check this, blowing compressed air into the tube will expand the bourdon tube on the back of the gauge and move the needle; I used a bike pump with needle to inflate a basketball to do this. Anyway, I then cut the donor gauge capillary tube near the back of the gauge, slid a section of shrink wrap tubing over the capillary tube, and fed the new capillary tube into the back of my gauge and soldered it up.

After all this, I checked my soldered connections and removed the bulb from the salt/ice water bath and place it into the pot of water. Here is where the depths of failure begin to sink in. On the big block logo SW gauge, the needle doesn't move at all...Ever. I thought at first I had soldered it shut, as mentioned above, but after re-submerging in the salt/ice water bath and pulling it apart, this was not the case. I have removed the bezel and lens from the gauges prior to this procedure, so I know the needle isn't froze up as I can move it and the bourdon tube and linkage assembly on the back all by hand with no issues. I can also rule out the possibility of a leak in the tube as I never smelled ether during the operation (don't ask me how I know about leaking capillary tubes, either....like I said....depths of failure lol).

In summary, here were my results:
Stewart Warner Greenline #1 : the needle has a 270* sweep and the gauge reads from 60*F - 240*F. Donor gauge: Equus w/ ~ 90* sweep and range 130*F - 280*F. The Frankenstein repaired gauge "works" meaning the needle will move from 60*F - 160*F. It won't move any more than that. So, I tried bending the little "U" at the back of the gauge that is connected to the link between the bourdon tube and the small gear mechanism that moves the needle. Now, the gauge is calibrated from 180*F - 212*F, but the needle will not return to rest at 60*F. It's new at rest position is ~ 160*F. Also, and obviously, the little gear mechanism near the needle on the back of the gauge is in the middle of it's travel path, hence why the gauge returns to rest at 160*F. If I gently push on the bourdon tube, the needle will return to 60*F, but it will not "rest" there.

Stewart Warner Greenline #2: The gauge is the same type gauge as the one above. I tried the same procedure using the same type (NEW) Equus gauge thinking I did something wrong the first time. Same result (eventually - first attempt it was soldered shut, second attempt I kinked the capillary tube at some point and got a refreshing dose of ether shot at me-yes; you guessed it: it was super fun, and third using a new gauge-again- I achieved the same results as Greenline #1). Exactly the same result.

Stewart Warner big block logo: The gauge also has a 270* sweep and reads from 100*F - 265*F. I started to think that maybe I was having problems with the donor gauge having a 90* sweep and my gauges having a 270* sweep, like maybe they have a different volume of ether in the bulb or something. I got another Equus gauge, this time with 270* sweep ranging from 130*F - 280*F. I did the same procedure but this time the gauge didn't move at all. Pulled apart and checked, not soldered shut. No smell of ether, no leak in the system. I dunno about this one. Frustrated, I transplant the 270* sweep capillary tube from big block to one of the Greenlines. Guess what? It reads from 60*F - 160*F.....

What am I doing wrong? I'm about out of ideas. I was thinking I'd try a different brand of gauge for my donor, but at least around here, the parts stores are either carrying an Equus gauge for $16-$20 or an AutoMeter for $50. I suppose I could order one from somebody elso online if any of you think that might be the issue, like maybe the Equus parts have a smaller mass and don't require as much pressure to move the mechanisms/needle or something like that. I also thought maybe the link between the bourdon tube and the small gear to the needle might need to be shorter or longer, but this seems pretty unlikely. I'm pretty sure I was accomplishing the same task by bending that little "U" riveted to the link. Like I said, I'm about out of ideas. Please help! And thank you in advance for any suggestions or information!

 

I d say that doing it yourself is your problem...Send your SW ga to Williamsons in Chester Ark to have it repaied correctly

 

I agree with you to a certain point. My current project has a functional Greenline temperature gauge, so I do not NEED this to be done. I just wanted to figure out how it's done, and I do not accept failure! Especially because I have several of these requiring repair (3/6 I have somebody cut), I would rather do this myself as it would add up pretty quick at $100/gauge or whatever they charge for repair. Obviously, my experimentation is adding up quickly also, but I have already learned way more than I would have if I just sent the gauges off along with a fistful of cash. I feel knowing how to do something is more powerful and useful than spending money to do have someone else do that something, so I'm trying to figure this out on my own (with the help of the internet and every other information resource avaiable of course!). But you are right in saying at this point I'd be better off sending them off if I needed it done. But I don't. I need to learn

 

times 2, they do great work, have done 3 sets of guages for me and getting ready to send them my 39 guages.

 

Try dry ice instead of ice/salt.

 

I'm in the school of "Knowing what I Don't know",....and am in agreement with leaving some tasks to those greater expertise and know-how.

4TTRUK

 

Have you tried the dry ice with success? I keep thinking back to the odor of ether, which has not been present, save for the one completely failed attempt. I have not tried dry ice, so I suppose it is possible that would work better. I just looked up the temp of dry ice: -109*F!! To those of you suggesting I send them off, thank you. I would likely use Morris Gauge as they are literally a mile from where I live, but that will be a last resort as the goal of restoring these gauges is to learn as much as possible rather than assume what the gauge restoration shops do is perform some sort of black magic and acts of wizardry.

 

I have not, but it seems that your issue with condensing the ether (and not getting enough expansion to display the top end of the scale) is temperature related. Adjusting the bourdon tube won't work for the original scale as it's not addressing the problem..... not enough pressure as the temp rises. That's a volume issue that condensing the ether further should help.

 

That makes perfect sense; I agree. Thanks for your help. I'll try to give this another go this weekend. If all else fails, I can just take some hits of ether in the fog of the dry ice....should be fun.

 

The guy is asking for help. Telling him to send it to someone else is not help.
That is not a good answer.

Stewart warner temp gauge fix.


Ago

 

Ago,
Thank you for the quick reply and USEFUL information. I will give this a shot as well with the two gauges that are already assembled. Also, thanks to fleetside66 for the PM. I noticed he'd posted in your linked thread above as well. I will reply with results, whether they be fail or win lol. Again, thanks.
-Tim

 

If a man made it, another man should be able to fix it !! Good for you! you'll figure it out! Chris

 

I'm all for doing it yourself! I try to fix anything .Before I quit ,it is fixed or junk. Good luck.

 

I Did mine last yr. It was the stock gauge in my Plymouth and when I tested it in boiling water, I have to say it was the most satisfying feeling to see it work especially since I was also told it cant be done.
Calcium chloride/water will get you the coldest bath. I cant remember the #s, But table salt/water is cold, rocksalt/water is colder, and calcium chloride was the coldest. Calcium chloride is basically the fancy "ice melt" that looks like tiney little snowballs.
I researched a lot before doing it and learned that the subzero slurry dosent freeze ether like you would think, Instead, it just turns the gas into a liquid. W/ that info, I decided to put my "ice water" and donor bulb on the floor so while working on the bench, gravity would help keep all the now liquefied ether in the bulb.

heres the pic verifying that it worked.


jeff

 

I'm thinking the OP's problem may have to do with the total volume of ether the original gauge used vs. the volume in the donor, and the volume of the respective bulbs & tubes.

I think too little ether or too much bulb & tube volume would result in not enough pressure exerted on the Bourdon.

I've done this repair successfully myself (with ice & table salt), but maybe I just got lucky that the original & donor were similar enough that any difference in volume didn't affect my gauge too much. I was able to "kink the link" and get it reasonably accurate within the range I cared about.

 

I just wanted to give anyone interested an update on today's experiments. I found this website which is very similar to the one already linked in my first post:
http://www.sunzeri.com/Stearman/tempgauge.htm
At the bottom it gives an e-mail link, so I sent a request for any advice/help. Here was his reply:
"Hello Tim:
What you've got is very similar to the experience I've gotten in repairing severa dozens of gauges. Some points to consider:

* Test the gauge to be repaired first. Using regulated compressed air, the gauge should read 230 deg. F at 100 psi air pressure. Fifty (50) psi should indicate very near 115 deg. F. If this doesn't test out correctly, the gauge's mechanism is worn beyond repair. Repeated cycles over the years will wear and harden the mechanism and the copper Bourdon tube, altering it's ability to indicate correctly.

* As long as the gauge to be repaired tests ok, then the only failure I've experienced is in cutting the capillary tube. From time to time I have to ream the opening to remove flash plugging up the tube as a result of cutting. I use a welding tip cleaner to clear the tube.

Cheers,
Jeff"

My shop w/ air compressor access is about 15mins from my apt, which is where I've been testing/soldering gauges as I have access to a stovetop here. I didn't get to the garage to test the gauges today, but will try tomorrow. I did notice the bourdon tube on my donor gauges is smaller than the Stewart Warners, so I started to think like others have mentioned that the volume of ether is too small of a vapor pressure to create a great enough force to move the needle the amount necessary on the Stewart Warners. So I went back to the parts store in search of the holy grail, but ended up with a 2 5/8" 270* sweep Autogage ranging from 100*F - 280*F. This was my only other option other than another Equus. I also picked up some dry ice and created a dry ice bath. Much colder temp of water (18*F), much higher quality gauge/capillary tube/, larger bourdon tube, etc. Things were looking good. I got it all back together............SAME RESULT. Bending the link as the link above shows yielded the same result as me bending the "U" near the link. The gauge will be calibrated from 180*F - 212*F, but returns to rest at 160*F. All 3 gauges did this. I'll be able to confirm w/ the compressed air check as to the condition of the gauge. It is likely that these have exceeded the mechanical limits of the constant cycling of the bourdon tubes. Probably what happened is the guage began ranging from 60*F - 160*F like I've been seening, and the owner got fed up with it, hacked off the sender, and got rid of the gauge. Anyway, that's my update thus far.

 

Okay, I figured I'd provide an update-again for anyone interested. I did not make it out to the garage yet to try the compressed air check. I've been working in my extremely sophisticated laboratory (kitchen) running experiments (screwing things up). The first few pics are where I was having problems with the capillary tube transplant not having enough uumph to move the needle enough on the gauge.

Here is the dry ice/regular ice/salt water bath for the bulb on the capillary tube of the donor gauge:



Here is the sleeve soldered to the back of the gauge and the capillary tube spliced in after the repair was completed:





Here is the gauge being tested with the bulb in hot to eventually boiling water. This is where problems begin to surface. The gauge was reading ~ 160*F at boil. I tweaked the kink at the end of the bourdon tube as mentioned in ago's link above. This yielded a gauge that was reading pretty well!







Now here's the main problem: after tweaking the kink, the guage is now at rest (the bulb is submerged in the ice bath in the pic) at 170*F!!! No good!

 

Looks good, so many of these are cut when the guy took it out of the dash and just thinks he is cutting a "wire"

or when the engine was pulled by someone who did not care

 

Tim
Do you know how large the bulb is that was on the original gauge? Maybe the replacement bulb does not have enough fluid as was already suggested.




Ago

 

Things were looking pretty grim at this point and I was about to give up, but I kept thinking about the vapor pressure of the ether not having enough force to move the needle-it was driving me insane (just read on-you'll see). Then, I for some reason got overly technical about it using Thermodynamics.

If Pressure = Force / Area (P=F/A), and I want force to increase, pressure has to increase.

If Pressure * Volume = # molecules * a constant * Temperature (PV=nRT),
and in a closed system Pressure(1) * Volume(1) = Pressure(2) * Volume(2)
---(P1V1=P2V2)---(1) being the pressure and volume of air in the capillary tube and (2) being the pressure and volume of ether in the capillary tube----and we are dealing with an isochoric process (volume does not change),
there was no way to get a greater pressure in the system within the temperature limits we're dealing with (this is why the gauge wasn't reading properly).....unless I modified the system! What if I took the volume of ether from two donor capillary tubes, combined it into one, then used that capillary tube as my replacement? Seemed like it could work, and since I've destroyed a handful of cheap-o brand new gauges and had capillary tubes to spare, why not try?
I don't know if this was the best way to go about this, but here's what I did:

I submerged two bulbs of my donor capillary tubes into the ice/salt water bath as shown earlier in this thread and in the links and gave them awhile to condense (about 10 mins-
I don't think you have to wait that long but I wanted this to work as good as possible).

In the mean-time I prepped a small copper sleeve and trimmed the protective rubber sleeve/coating off the ends of the donor capillary tubes.

I then cut both capillary tubes and soldered them together with the sleeve. I inspected this very carefully to make sure I didn't screw it up.

Then, I boiled a pot of water on the stove and placed it as high up as I felt like lifting a pot of boiling water over my head.

I submerged one bulb in the hot water and left the other bulb in the ice bath.

I moved the ice bath to the floor.

The idea was to get all of the ether to heat up, expand and travel down the tube to the cooler part of the system (going from hot to cold-maximum temperature differential). I have no idea if it would work better to put the hot water on the floor and the ice bath elevated (the whole heat rises bit).....I felt like gravity working in my favor would be better. I waited for probably 15 minutes, then de-soldered the two, soldered the ice bath capillary tube to the back of my gauge, and soldered the boiling water capillary tube shut (in case it didn't work or there was residual ether in there-a safety precaution basically).

I checked my soldered connections on the gauge, put the hot water back on the stove and brought it to a boil again.
Keep in mind the previous attempts with this particular gauge yielded a measured boiling temperature of 150*F.....Not so stellar.

Well, I submerged the bulb, watched the needle climb from rest to...........197*F!!! (Note: I took the picture a bit early as I was ecstatic something actually worked for a change) It worked! Reading 197*F at boil is a 7% error, which is within "tweaking" using the info from ago's thread link. Success!!!

Anyway, in summary, if anyone ever tries this, attempt a 1 capillary donor gauge repair, and if it fails, throw the gauge in the freezer and go pick up another donor guage and follow this procedure. It worked.





And here's the project which required a ridiculous hunt for gauges to get a matching set:

 

Congrats on figuring this thing out Tim. And thanks for sharing your info.
Jim

 

Going to be attempting this very soon, I was thinking of putting the gauge in the on an angle so gravity can pull the ether to the bottom. Then possibly doing a calcium bath to keep the bulb colder. Another thing I was thinking too was wart remover the freeze off kind I think is something near -41 degrees and spraying part of the tube with that before my solder joints.
Thanks for the info on all your trial and error.

 

How about dry ice, a block of dry ice has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C).

 

Its all about having the correct volume of ether in the bulb and correct size of bulb plays into this.
Putting the bulb in a household freezer is cold enough for what you're doing but dry ice makes damn sure.

 

As mentioned above, the volume of ether is critical to accurate gauge readings. I used dry ice when I tried this as also mentioned above. The reason I had to splice 2 tubes to one, then back to one was to get the correct volume of ether. A graduated cylinder similar to what the titration lab you did in high school chemistry would be better, then you would know how much volume you were dealing with and could use how far off your gauge is to establish a ratio to add more. I'm not sure where to just get ether.... I have read John Deere starting fluid has high ether content, but I'm not sure it would work. Been meaning to revisit this and try just that with a cylinder head cc kit to add it in if that makes sense.

 

You can move the linkage for minor adjustment

 

Tim back in the 50s we would get ether for racing from the drug store. Probably need a prescription today if they even carry it.

 

Wish I had seen this post a couple years ago.
You definitely have way more patience than me I tried a couple times and called summit racing for a $$ repro greenline and probably tossed the old one out, can't remember.
I did have success adapting a sun tach guts to the greenline tach however.
It still drives me nuts to have one shiney new gauge next to a weathered original!

 

I've only done it once but it worked fine for me.
I used an inexpensive aftermarket gauge with a 1/4 sweep indicator as a donor
for my original mid '30s Chevy gauge with similar sweep.
'had my original gauge prepped and splice tube ready,
plunged the donor bulb in regular old ice water on the floor
let it cool for a few minutes,
and with the rest of the stuff on the work bench
cut the tube, put both tube ends in the splice tube and quickly gave it a touch of solder.

I tested it in a pan of water on the stove
brought it up to boiling a few times plunging back into the ice water between
giving several hot cold cycles to make sure it wasn't going to bleed down.
every time the gauge read a little over 210 at boiling, good enough for me.

'been running it for a few thousand miles now with no issues.

 

^This has been my experience as well about half the time. The other times they need more ether. In the next few months I have several gauges that need repair, I will try to come up with a repeatable process and report back. Thanks to all who contributed to this.