Talk Morgan Forums Morgan Sports Cars Morgan Aero 8, 2012< Plus 8, SuperSports, Coupe & Aeromax Coolant Temperature Observation and Question

The run to Williams was the first cool drive of the season: snug enough with heated seats and hot air blowing, but the water temperature gauge seems to know when it is cold outside.

All summer the gauge has sat at between 95c and 98c, irrespective of speed, load, air temperature or anything else. But when it is cold outside it is at between 100c and 105c, dropping back to the "summer" reading when it is over 12c outside.

This is the third winter I've had the car, and the third time it has shown this effect. I'm not concerned, it never goes above 105c, but for the life of me I can't work out WHY it does it. Any of the Aero specialists have an explanation?

It is almost as if the fan has two sensors, water temperature and external temperature....or is the fan controlled by the ECU? suggested it is to do with the clocks going back, but i'm not buying that!

I noticed this the other day when i finished filling the rad but thought no more of it until now. It could be that due to the lower outdoor ambient temps the thermostat body changes shape/size and this affects the callibration?

Has it got an external air sensor that controls the thermostat so that you can keep your tooties warm in winter.

Guess.

I use the aircon during summer and leave it off during winter. Does the A/C cause the fan to run constantly and so result in a drop ? In winter no A/C and so only main engine fan which kicks in higher ?

Just a guess ?

I use the A/C on my smart Roadster to force the coolant temperature down when in hot slow traffic - So I reckon Alistair could have a point.

Try putting your A/C on Peter see if it brings the temperature down - Yes you can run it on hot temp settings but it may not actually run below 5°c air intake

I have a similar strange one on my Impreza in August and September I was getting a P0420 code every 20 miles or so.

Since the temperature has gone down below 10C not one error code

The A/C causes the engine to idle at 750 rpm, not 500 as usual and yes, the A/C fan does bring the temperature down.

I'm beginning to think that the radiator fan is controlled by a combination of data, from engine and external temperature and status of the A/C. All this stuff is BMW, after all.

Well thats the catalyst not working right code which could either be the catalyst or the second lambda sensor. Not obvious why temperature should affect this - it could even be that you drive differently when its colder. Either way the sensor or cat are on the edge and higher termperatures tip it over.

Sticky thermostat?
Colder temp might show it up more, thus affecting the amount of water flow and side effect being less cooling - more heat.

Hmm maybe a long shot tho.

Mine does the same Peter - reads a higher engine temperature in colder weather.