Smiths Gauge worry.

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midget
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Smiths Gauge worry.

Postby midget » Thu Jun 06, 2019 8:51 am

Have completed the restoration of my Van, and have fitted a capillary type dual (oil/water) gauge, as fitted to MGB/Midget etc.
The temperature part wavers constantly in the lower third of the scale, as soon as running temperature is reached. I have used these gauges previously, but have never encountered this?
New Rad,refurbished Mini heater and pipes were fitted, and I have no Cylinder head mounted valve. AFAIK the engine does not overheat. I would not have thought that a faulty thermostat would give these symptoms?
Any thoughts please?
John

Chipper
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Re: Smiths Gauge worry.

Postby Chipper » Thu Jun 06, 2019 12:33 pm

What engine is it, and what temperature thermostat do you have fitted?

You could try temporarily blanking off the radiator with cardboard, to see if the reading goes up beyond, say, half-way, which would at least verify that the gauge is working beyond the lower part of the range.
Maurice, E. Kent
(1970 Traveller)

midget
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Re: Smiths Gauge worry.

Postby midget » Thu Jun 06, 2019 2:41 pm

Its bog standard 1098 Saloon engine and as stated, a Smiths dual gauge which has a capillary type function as compared to electrical.
It is mounted at the front of the head on the right hand side. :wink:
I will deliberately overheat it and observe (currently it never travels past the 1/2 way mark) but I would have thought that as they are quite common with BMC products, someone may have experience with this query.
John

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Re: Smiths Gauge worry.

Postby Chipper » Thu Jun 06, 2019 6:44 pm

Bear in mind, they were originally intended for MGB/Midget fitment, where their engines probably run quite a bit hotter than the Minor's over-cooled setup.

The Smiths electric gauge in my 1275cc Midget-engined Traveller usually sits at around half-way only after a long high-speed run or in traffic on a warm day. It only ever goes above half-way if I'm going up very long steep hills, or if there's some problem.
Maurice, E. Kent
(1970 Traveller)

midget
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Re: Smiths Gauge worry.

Postby midget » Thu Jun 06, 2019 7:30 pm

Thanks Maurice. That's exactly what I expected with my previous experience with these.
BTW, I follow your posts on "another" forum.
John

JOWETTJAVELIN
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Re: Smiths Gauge worry.

Postby JOWETTJAVELIN » Thu Jun 06, 2019 7:37 pm

My Midget used to run at 50 deg. C. which is far too cool - it wastes petrol and contributes to engine wear - until I changed the thermostat for something like an 82 degree one, now the coolant temperature sits at an ideal 70 deg. C. You want the engine to run as hot as possible for efficiency, 70-80 deg. C is ideal. You could also check the capillary gauge for reasonable indication by boiling a pan of water and comparing readings with a scientific thermometer.
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paul 300358
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Re: Smiths Gauge worry.

Postby paul 300358 » Thu Jun 06, 2019 11:52 pm

I tested my 1098 a couple of weeks ago, it has a 82 deg thermostat in and it ran between 83 and 85 deg at the top of the radiator whilst sat ticking over. Tested with a calibrated digital thermometer.

midget
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Re: Smiths Gauge worry.

Postby midget » Fri Jun 07, 2019 10:11 am

Thanks for replies which I understand and agree with completely, but it is the fact that the gauge swing back and forth constantly as soon as running temperature has been reached.
Every other gauge of this type which I have seen and used remains constant with only small movements either way relating to conditions.

To repeat, it never moves past the 1/2 way, but is constantly swinging (slowly) between C and 1/2 way section. Not the full part of this section, but about 1/2" of it.
John

MikeNash
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Re: Smiths Gauge worry.

Postby MikeNash » Fri Jun 07, 2019 12:30 pm

Dear Mr Midget,
May I suggest that you take out the capillary sensor end and place it in a kettle of boiling water? With luck you should be able to get an electric kettle on an extension lead under the bonnet and so test the temp gauge for a steady reading of 100C, the critical point. (It should read within a couple of degrees of this figure.) This would give you confidence that there's nothing with the gauge itself. (A handy wine bottle cork should fit the sensor hole and reduce coolant loss.)

I've had two of this type of gauge fitted for years (one for water and the other for oil) and their nature is a relatively accurate and steady reading, so if yours is waving about I think it's trying tell you something! I assume yours is in the head just below the thermostat and so I'd suspect that the latter is playing up. Thermostats aren't what they were, the old bellows type was accurate and would fail completely open i.e. safely, but the modern type fails shut - bad news! But now as they approach failure they can be all over the place; I've tested a few and they can fail by only half opening (or less) or the temperature at which they open drift up or down. Even when brand new they can be a few degrees C off their nominal specification.

At the moment I've a 82C thermostat fitted but in the past I've run a 89C happily for years. That made a significant improvement to the heater! I'd try a 91C which some parties have recommended in the past but I can't find one.

Regards from MikeN.
Morris Minor, the car of the future. One day they will all look like this!

midget
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Re: Smiths Gauge worry.

Postby midget » Fri Jun 07, 2019 12:49 pm

Thanks Mike, that's interesting.
I dismissed the thermostat as very unlikely, but will replace this as you suggest.
The only thing that I have not mentioned is that the engine and drive train have not been touched during the 3 year restoration (as they did not need attention) and the gauge is an additional upgrade, so the thermostat could have deteriorated in that time?
John

midget
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Re: Smiths Gauge worry.

Postby midget » Thu Jun 20, 2019 2:09 pm

Just to confirm that a replacement thermostat did indeed cure the wavering gauge readings.
Thank you.
John

MikeNash
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Re: Smiths Gauge worry.

Postby MikeNash » Thu Jun 20, 2019 9:11 pm

And thank you too for completing this thread! MikeN.
Morris Minor, the car of the future. One day they will all look like this!


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