Lotus Elan

Smiths dual oil/water temp gauge repair?

PostPost by: tomjones20194 » Wed Dec 19, 2018 2:25 am

Folks,

The water temp sensor (bulb) has been removed from the cylinder head and the capillary has been cut about 3” from the rear of the gauge.

Can this be repaired? Where can I buy a new sensor and water capillary tube?

Thx
Tom
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PostPost by: nmauduit » Wed Dec 19, 2018 8:18 am

the capillary bulb sensor tube can be repaired, but it is not a mechanical repair in that the volume represented by the bulb and capillary tube attached to it must be soldered gaz tight while sealing a quantity of dietyl ether within the bulb (evaporation temperature 34°C : keep the bulb with liquid ether in iced water while soldering). If the tube has been cut one way to repair it is to source a slightly larger piece of tube that can be soldered ID on OD.
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PostPost by: Elanintheforest » Wed Dec 19, 2018 11:28 am

They have been re-made for S3 onwards.....

https://www.ebay.co.uk/itm/Genuine-Smit ... :rk:1:pf:0

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PostPost by: pharriso » Wed Dec 19, 2018 11:47 am

Thanks for Posting MArk, they seem to have many of the gauges for our cars. :D
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PostPost by: billwill » Wed Dec 19, 2018 12:27 pm

The 'sensor' is the vapour pressure of the fluid which is commonly called just ether. It can be difficult to get hold of, but has been available in 99p shops as a coldstart spray can. {alas no more 99p shops}.

The thing in the visible gauge is a normal Bowden pressure meter (?) , quite similar to the oil pressure half.

I've been meaning to do mine for ages, but not done so yet.

The bulb end needs to be about half full, (not full, which would measure thermal expansion of liquid instead of vapour pressure).

Depending on how much capillary tube is still connected to the bulb, my proposed method of repair would be.
1 get some ether in liquid form in say a glass surrounded by ice.
2. warm the bulb to drive out some vapour then cool it with the tip in the ether so that it will suck in the fluid, repeat until you think it is about half full.
3. keep the bulb in ice until ready.

It would be all too easy for solder to block the capillary entrance so:

4. get a piece of brass (rod, round or square or hex) about 2 inches long and drill a fine hole lengthwise which is a close clearance hole for the capillary pipe.
5. poke the gauge end of the pipe about an inch into the hole and solder it in at the rod end.
6. keeping the bulb cold, poke its end of the capillary tube into the rod until it almost meets the other part of the capillary tube.
7.Solder it in at the end.

The above process should keep the solder away from the tiny hole in the ends of the tube.

Test by dunking the bulb into boiling water, carefully.

Or
Send the whole thing to Speedy Instruments (?) :D

or buy one of those mentioned above. 8)
Bill Williams

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PostPost by: tvacc » Wed Dec 19, 2018 11:07 pm

This is really simple if you know how to solder. I have an article on http://www.lotusowners.com about the process. Takes me about 10 minutes.
Go to the Repairs/Upgrades section of the website and look for the link.

Basically you just go to an auto parts store and buy a cheap bulb type instrument. About $15 here in the USA at Advance Auto. Then you make a salt/ice bath, super cool the bulb, cut the tube and solder it back in place to your old gauge.

I have done about 5 of these and they all work fine.

Tony V

Edit.....just looked at my website and the link I have on it to the original article does not work any longer. If anyone needs some help with this, just let me know. I just bought a used gauge (dual) on eBay for $25. I am going to pick up a $15 gauge at Advance and do this again to have a spare. I will take more photos and update the site. If you need help, email me at tvacc*at*lotusowners*dot* you know where. If you want me to do this for you, just send me your gauge and I will fix it for $30 plus the cost of the gauge from Advance and return shipping to you. I will then donate the $30 to the LOONYs.
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PostPost by: Bud English » Thu Dec 20, 2018 12:17 am

Tony, slight thread drift here, but do you know if your method works to repair the ambient air temp gauge on the +2? It seems like it should, as the gauge is based on the same principle but at a lower temp range.
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PostPost by: tvacc » Thu Dec 20, 2018 12:35 am

Bud English wrote:Tony, slight thread drift here, but do you know if your method works to repair the ambient air temp gauge on the +2? It seems like it should, as the gauge is based on the same principle but at a lower temp range.


I have never tried it on a plus 2 air temp but I don't see why not. Ether works the same way.

It is so cheap that it is worth a shot.
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PostPost by: prezoom » Thu Dec 20, 2018 5:02 pm

Tony, what is your source for ether? Starting fluid?
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PostPost by: tvacc » Thu Dec 20, 2018 6:20 pm

prezoom wrote:Tony, what is your source for ether? Starting fluid?


The source of the either is the cheap temp unit you are buying. There is ether in that bulb. When you super cool it with ice and salt down to below 37 degrees, the ether stays in the bulb from the new unit while it is bathed in the ice and salt solution. You keep it in the solution while you are cutting and soldering. I use a cut off wheel from a Dremel to cut the tubing. I use a sewing needle to ream out the center of the tubing after I cut it.


The ether only comes out of the bulb to go the gauge when it goes above 37 degrees.
If this is not clear, let me know. Happy to help all I can.
Tony
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PostPost by: prezoom » Fri Dec 21, 2018 12:29 am

Thanks Tony, got it. Guess with the 37 degree thing, I will never get an ice warning here in SoCal. All kidding aside, there is a bridge on I-15 that can get black ice. Plays heck with the commuter traffic on cold mornings.
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PostPost by: tvacc » Fri Dec 21, 2018 1:40 am

The 37 degree thing has nothing to do with out side temp. That is the temperature that ether turns to liquid. You will find that plain ice in water will cool the bulb to 36 to 37 degrees. By adding salt to the ice, you get down to 32 or so. At that temp, the ether is a fairly stable liguid and will stay in the bulb in the salt/ice bath.
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PostPost by: Elanintheforest » Fri Dec 21, 2018 9:28 am

prezoom wrote:Tony, what is your source for ether? Starting fluid?

I'm not sure starting fluid is pure ether so may not work. But you can buy ether on ebay, with one of it's uses being 'recreational' !! Really??

https://www.ebay.co.uk/itm/100ml-Diethy ... 1237608713
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PostPost by: nmauduit » Fri Dec 21, 2018 10:26 am

you want pure enough diethyl ether, otherwise the resulting partial pressure of the mix won't be actuating the gauge properly when in operation (ebullition point at 34.6°C diethyl-ether)... I've seen online offers of small quantity flasks of diethyl-ether stabilized with up to 2% of ethanol and marginally other stuff which should be fine for Smiths purposes (no need of the 99.9% exepensive lab grade I think), but I'm not sure about the actual content of starter fluid spray cans...
__
edit: just seen the above link, might get a refill myself, 99.9% pure stuff not that expensive is probably a better bet for predictable operation (unless someone knows the actual composition of the fluid used at Smiths to be different of course)
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PostPost by: rcraven » Fri Dec 21, 2018 10:51 am

It would avoid possible confusion if people posting here all stated expressly whether they are giving temperatures in Fahrenheit or Celsius. I can guess but it's better not to have to.
Ether is dangerously flammable.
A google search comes up with some repair instructions with illustrations.
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