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MG MGA - Thermostat accuracy

I recently bought a cooler thermostat, 74degC(165degF) thinking that it would be more suitable as I was never going to use the car in the winter months. The one I was going to replace is an 82degC (180degF).

Before I made the change I thought I would check the opening temperatures so put both in a pan of water with a thermometer. The 74 stat started to open correctly at 74deg but the 82 stat was already open at this temperature and had started at 70deg!

It was a bit difficult to estimate but both units were fully open at 90deg. Over the 20 deg range the 82 stat opening aperture was always that bit wider than the cooler one.

Both stats were stamped with their opening temps 74 and 82 and the latter was also stamped 'made in england'! Both were visually very similar in construction.

Needless to say I put back in the old one.

But if you intend doing something similar it would be worth carrying out the check................Mike

m.j. moore

Not that surprised.

I have often wondered when we hear discussions about engine temperatures how accurate our water temp gauges actually are. In reality it doesn't matter very much as it is change in temperature that is more important than actual precise temperature.

Paul
Paul Dean

One thing that should be done is to suspend the stat in the water,if it lays on the pan bottom it will pick up the heat and give you a false indication. I had heard years ago that the gauge in modern cars is not an actual reading like the ones in our MG's. You never see the temp vary in modern car,but our Ski Nautique with a 5.8 will change temp. It runs 160 on a 160 stat but work it hard and the temp will go up 5-10 degrees. Shut it off and the temp will go up to 200 due to heat soak. You never see that in a car. Our newish BMW does not even have a water temp gauge just oil temp
gary starr

I suppose progress has done away with the thermometer and even the ammeter in 'modern' cars. The pressurized cooling system has probably put paid to the thermometer and the alternator has seen the back of the ammeter.
I can remember that it was a very common sight on the roads in the 1950s seeing prewar cars that had broken down at the top of a steep incline with steam issuing from their radiators....... Mike
m.j. moore

This thread was discussed between 29/08/2015 and 31/08/2015

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