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MG TD TF 1500 - Boyce Motometer

I own (or rather, I am owned) by a 1950 MG TD. Originally built without a water temp gauge but one was added by a PO. The gauge appears to be failing fast or the Duchess is running really cold.

In any event, I was considering installing a Boyce Motometer on the radiator cap rather than replacing the gauge in the dashboard (looks to be from a TC).

Does anyone have any experience/insight on the utility of Motometer vs. a Jaeger gauge? Price for a rebuild about the same as a Motometer installed in the radiator cap.

Picture of the Duchess attached.

Charlie Duffy
Healdsburg, CA

Charles Duffy

A 3rd option, Charlie. If you're a bit adventurous you might consider repairing your present gauge. It has probably just lost its ether. Check the archives. Bud
Bud Krueger

Must have been made by Lucas, the ether got out.
Jim Neel 53TD28423

Charlie - Before investing in the Motometer or a new gauge, check the coolant level in you expansion tank. If the coolant level is not high enough to cover the temperature gauge bulb, the gauge will not display the correct temperature (same thing with the Motometer, the bulb has to be submerged in the coolant to give a correct reading). If this turns out to be the problem, consider installing a coolant recovery system as described in the article, Expansion Tanks, Coolant Recovery Systems and How the Cooling System Works in the Other Tech Articles section of my Homepage at:

Bud's suggestion of refilling the sensor tube is valid for the brave, but before doing that, I would suggest that you check the dial itself for being jammed. Cheers - Dave
David DuBois

Dave, Bud,

Thanks for the suggestions. Dave, the bulb is making contact with the coolant; I just had the radiator recored because it was so clogged the radiator shop could not boil it out!

Jim, yeah it sounds like another adventure with Lucas but it is a Jaeger gauge, likely made by Smith's
Charles Duffy

I am worried about a genuine MG-TD being referred to as DUCHESS. There was a company that placed Replica TD's in airport using airport transfers sevenoakss and they were VW powered. They called them DUCHESS.

Charlie, consider sticking if the needle isn't coming off of the peg. You could try pulling the sensor out of the back of the radiator and sticking it into a pot of hot water to see if the gauge registers at all. Take a look at the capillary tube, probably covered by a coiled-wire. If there are no obvious leakage areas (usually discolored, or rusty) then you're probably just suffering from the loss of the ether from the tube. You might want to check the archives on this topic. For about $20 and the use of a soldering iron (no flames) you can do a bulb transplant. Bud
Bud Krueger

Since most T-type radiators tend to seek their own level - usually just above the core, a Motometer will often not reach down enough into the coolant to give an accurate reading, if any reading at all.

I personally think they are ugly, besides.

Lew Palmer
Lew Palmer

The trick to getting a Motometer to work properly is to wrap a piece of heavy copper wire (10 gauge, no insulation) tightly around the end of the Motometer, and tighten it with by twisting a loop with a pliers; then have the other end dip into the coolant. I bent the other end into a loop so that it was rounded at the end.
Ira Spector (PA)

in regard to moto-meter..lew's post reinforces the old adage "beauty is in the eye of the beholder"..i happen to like the look..but to each his own. in regard to the accuracy of the meter... the meter does not have to be immersed in the coolant as the car sits prior to starting. as a poster points out, the coolant will seek it's own a car with or without a coolant recovery tank..that level is the over flow tube. all moto-meters stick down below this level...if your car is under in the coolant is so low it never reaches a point near the over flow tube...the vapor above the coolant will be within a few degrees of the coolant this case the meter will give you an accurate enough reading for what you need...which is a change from what you normally read. regards, tom
tom peterson

Our TD came with a Motometer in the radiator cap. The interesting thing is that it and all the other Motometers was facing the wrong direction - with the temperature scale facing the driver. Think about it, the driver is too far away from the Motometer when sitting behind the wheel to read the scale and when the car is stopped and the driver walks to the front, he/she can't read the scale because it is facing the wrong way. The Motometer scale should be facing forward so it can be read from the front of the car. While the car is being driven, the driver should see just the round, clear circle in the motometer so that if the car overheats the red fluid can be seen through the clear circle. Cheers - Dave
PS. I'm with Lew, I don't like the looks of a Motometer on a T series car.
David DuBois

I have an extension on mine and a rubber seal which stops the coolant leak from the cap as I have an expansion tank fitted.

Declan Burns

We've used a Motometer for many years along with temp gauges. Motometer has always been reliable. I did add a copper tube to the bottom to dip down into the coolant, but it no longer has it. The coolant normally expands a couple of inches higher, but in all actuality, the air temp above the coolant is a reliable enough media for a temp reading, anyway.

We have the thermometer scale aimed towards the back as the red alcohol is adequately visible, as long as it is aimed at my wife, the driver. The thermometer is sort of triangular in cross section to magnify the alcohol. She does keep her eye on it, too! My vision is better than my wife's and I can make out the thin red line with no problem from the unmagnified side.

There has been an air bubble that has a little slug of alcohol propped up in the thermometer, but it is still very readable. I've stuck that sucker in the freezer and it seemed to recombined the alcohol, but that darn bubble has reappeared. Try, try again.

The only downside to relying on the Motometer alone, is driving at night!

My TD only had an oil gauge & a motometer...I always wondered if the motometer was accurate...spent years in Boise ID driving in 100 degree temps & 6000' altitude and the motometer always showed normal...sourced an oil temp/water temp Jaeger gauge and installed it...compared my motometer readings with my temp reading...they were spot on! Motometer showed optimum temp when the temp gauge showed 80-85 Celsius....
Bob Dougherty

This thread was discussed between 13/06/2013 and 18/06/2013

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