British-Cars.org

Welcome to the DMR Site for British Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Opening/Calibrating Temperature Gauge

More about it later, but I have been successful in refueling the ether of Lazarus' temperature gauge. With the bulb in a pot of boiling water the needle comes to rest at about 90 psi on the oil pressure scale. The next step is to calibrate the gauge. Anybody ventured into one of these things? There are three screws on the underside of the gauge (shown below). Any chance that they hold the works into the housing? Tnx. Bud

Bud Krueger

Bud,
You've got mail.
-David
D. Sander

I urge extreme care in using ether.

Ether is the name for a class of organic compounds. It is not a single compound. Diethyl ether (also called ethyl ether) is the most common ether and may be what is in the MG temperature gauge. There are other ether compounds, however. (Just like there are many different alcohols, for example, methanol (methyl alcohol), ethanol (ethyl alcohol), propanol (propyl alcohol), etc.)

Ethyl ether is very volatile and very flammable.

The biggest concern, however, is that ethers degrade and form organic peroxides to some extent. At the extreme, just jostling an older container with ethyl ether could cause the material to explode, as organic peroxides are contact explosives. This is uncommon, but not unknown.

I'm glad this question came up. Perhaps the most important thing we can do as participants on this Internet discussion board is to help each other stay safe, so that all of us can continue to enjoy our cars. As I have extensive training in chemistry, I am pleased to share what I know about these matters.

This gives new meaning to "SAFETY Fast!"

Larry
Larry Shoer

In this case, what I've done is to splice the tubing from a new, inexpensive, temperature gauge into the tubing of the TD's temperature gauge using a soldering iron. While performing the operation the ether bulb of the donor gauge was immersed in a tub of ice water. Bud
Bud Krueger

Bud,

What you described is a good way to do it. The only other thing to suggest would be doing this when the humidity is low, as moisture trapped in the tube would degrade the ether over time.

Larry
Larry Shoer

Bud - For calibrating the gauge, first remove the gauge from its case and look at the Bordon tube and the attached gearing. There is a rack gear attached to the Bordon tube that rides on a pinion gear attached to the needle. Check that this gearing is such that there is enough range at either end of the rack gear for both minimum and maximum reading (extra space on the rack gear to allow the reading to go well above 100° as it is not uncommon for the temperature needle to go clear into the oil pressure range if you have a dual gauge). As long as there is plenty of range at either end, you can just remove the needle (two screwdrivers - one on either side of the shaft, with something to serve as fulcrums under the screwdrivers, then just pry up evenly on both screwdrivers at the same time - it is a good idea to put a handkerchief over the needle to keep from launching it into orbit when it finally comes loose). Put the needle back on the shaft so that it points to 100° with the bulb in boiling water (at sea level. The low temperature may be out a bit, but that is not the end you need to worry about. Cheers - Dave
David DuBois

Many thanks, Dave. First question --- How do I remove the gauge from its case? I do recall the time, late in a 4th of July parade when the needle was well into the oil pressure side:


Bud Krueger

When I had the overheating problem with the MGA the tempature would run at about 90 lbs of oil pressure. Now it rides right at 190' but goes up to 230' when I turn it off.
- David
D. Sander

Bud - If I remember correctly (It has been nearly 30 years since I fussed with the gauge) there are some screws in the back of the case that can be removed and the gauge innards and the face can be pushed out of the case. Cheers - Dave
David DuBois

Okay, got it disassembled. Surprise, surprise -- there are no adjusting screws in these mechanisms. Any adjustments are by physical tweaking. Both gauges are virtually identical with the oil pressure mechanism having a larger base piece to fit ahead of the water temperature mechanism so as to allow both to fit in the case. Only real adjustment is by positioning the needle on its shaft to give a reading matching a known input, such as a pot of boiling water. Bud
Bud Krueger

Just a shot of a couple of useful tools I have used for removing needles from guages, clocks etc. You can usually find one at a good hobby shop. Cheers Phil

Phil Atrill

Gorgeous instruments. A problem I've run into isn't in removing the needles, it's in reinstalling them. The needles are close, but not quite, interchangeable. Putting the oil pressure needle on is not a problem. It's thye water temperature needle that is a problem. The needle must be installed at the 100C position while the ether capsule is in boiling water. It must be firmly installed to avoid having the needle rotate about its shaft when it comes to rest against the low end stop. I'm still working on that. Bud
Bud Krueger

Bud,

I use a common dinner fork to lift needles off posts (crude, I know). I gave it very little thought while I had the capsule in boiling water, and then set in place the needle. Ignorance is bliss, because it has worked flawless since. Even to the point of reading ambient temperature on hot days! The temperature needle, incidently was a gift from Dave DuBois after the combination gauge flew across the garage in a cleaning accident! I think he got it from an MGA... and it looks good.

warmly,
dave
Dave Braun

Bud - A piece of 3/16" dowel with a hole drilled in the end to clear the shaft. Tap the needle down once it is positioned. If you are concerned about it being tight enough, a small bit of locktite will ensure that it stays in place (just don't leave your name on the gauge or the next person trying to remove the needle will be looking for you whit homicide on his/her mind). Cheers - Dave
David DuBois

Dave B. -- I have a pair of angled needle nose that do the job beautifully. Thanks.
Dave D. - I give the dowel tap a go. Locktite would be an absolute last step. I may well be the next person. Bud
Bud Krueger

This thread was discussed between 15/12/2011 and 18/12/2011

MG TD TF 1500 index

This thread is from the archives. Join this live forum now