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SP250 Thermostat

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John-B
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Re: SP250 Thermostat

Post by John-B »

Mpringle wrote:And BTW, John-B, phill more,DavidS and Ian,
What thermostat do you use?
Cheers,
Michael
I didn't buy my thermostat, but I'm sure Phil Glennerster will be willing to talk to you (tel. +44 (0) 1189 340927).

When driving at 70mph in hot weather my temp. gauge also shows at about 1.30pm position, slightly over the mid-point. Last year the electric fan did come on for a short while driving at 70mph and, as you said, shouldn't come on if you are driving fairly fast. I re-set the electric fan thermostat just a fraction higher and now it only comes on when idling for about five minutes on a hot day.

Phil said that it's not a good idea to set the electric fan to come on too high as it increases the range between cut-in and cut-out, which means the cut out temp is lowered, which might mean that although it will cut-in at a higher temp. the coolant never gets low enough to turn it off!

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Ian Slade
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Re: SP250 Thermostat

Post by Ian Slade »

I've never used a special to type cooling fan, I made my own years ago out of a heater fan motor and a Ford Corsair plastic fan mounted in front of the radiator which I turned on when required, except for racing it has never risen above 90degC at above 40mph. The system is pressurised, therefore the water will not boil at 100deg C, the actual problem comes from the water either boiling away or being thrown out and not replenished from a catch tank or expansion tank, the SP needs a second tank, replace the fitted expansion tank cap with a non pressurised cap and fit the pressurised cap to the second expansion tank. What thermostat it has now I'm not sure but is was a recommended one for the car from after market spares catalogues. From my experience providing the temperature is below 100degC it is OK and preferably below 95degC. trying to keep the car above 1000rpm in the highest gear possible and the fan on below 30mph would be the ideal.
Owner since the 70's, Genghis is slightly to my left.

Phillmore
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Re: SP250 Thermostat

Post by Phillmore »

I don't have an SP but when I removed the head from my Conquest recently I discovered that there wasn't a thermostat in there!
Andy

1954 Conquest Mk1, 1956 Conquest Mk2, 1957 Conquest Century Mk2, 1955 Austin A90 Westminster

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Ian Slade
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Re: SP250 Thermostat

Post by Ian Slade »

That does give you optimum flow in summer, not so good in the winter, and whatever time of year a slow warm up, so a bit thirstier than usual
Owner since the 70's, Genghis is slightly to my left.

Andrew D
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Re: SP250 Thermostat

Post by Andrew D »

I run my SP on a 75 degree thermostat as recommended by Phil. Glennerster. I have used the car in quite high temperatures, in the south of France for example. I find that the temperature gauge, while moving, is at the lower level of the white band, rising when stationary at which time the electric fan cuts in. I have an aluminium radiator fitted.
Hope this helps Michael.

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Marc Mears
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Re: SP250 Thermostat

Post by Marc Mears »

When I got my car in bits (from the USA) - it came with a few different thermostats and these were of differing temperature openings.
I believe they are called summer and winter thermostats – but I guess someone will correct me on that
I opted for the lower one, as I reckoned that my car would be used mainly in summer…. And fancied the idea that it ran cooler when I take it over to Le Mans Classic this year.
I think the two thermostats have opening temps of 75 oC and 85 oC
So these are my findings using the summer one…. The 75 oC
The car does not get up to middle of the gauge 185oF/85oC when around at 45/50 mph on days that are 15 oC or lower, the temp gauge gets to the lower part of the white arch and I recon this is about 70 to 75oC and that ties in with the openings of the thermostat – A revelation!
So it seems to run at 10 oC colder than normal 82/85 oC but does get up to the higher temp when thrashed…. But hardly never goes over the mid part of the gauge when its in motion
The car runs well and does not seem to be unhappy running a little colder in some conditions.
I have an electric fan that hardly ever cuts in – only after fast driving and then held up in stationary traffic or lights does the gauge creep up and then the fan cuts in
Hope it helps
Daimler Dart. Healey 3000 Mk3. VW T2 Camper. BMW 2002tii. 996 Turbo. BMW Z3M. Hillman Tilly. Rolls Royce 20/25. XK 150 ots .BMW 3.0 CSL 73. Sunbeam Alpine Mk3.Morris 8 Tourer. 97 XK8 Convertible.Alfa Romeo Giulietta. Citroen Mehari

Crossley Stephenson
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Re: SP250 Thermostat

Post by Crossley Stephenson »

Thanks everyone for your responses. It appears that most of us don't know what thermostat is installed in our cars; including me. I will be flushing the block and radiator soon and as part of the process will also replace the thermostat. I intend to use a 76c thermostat (as recommended by Daimler) despite being supplied with a 86c thermostat by one of the SP specialists. A 76c thermostat ensures speedy warm up and full coolant flow from about 80c. The normal operating temperature is between 80c-100c and a warm engine is more efficient than a cool engine. An electric fan should be set to come on a few degrees warmer than the point at which full coolant flow is achieved and given that a pressurised cooling system with a good coolant has a boiling point considerably higher than 100c it should be safe to set the fan to come on around 90-95c. According to Davies Craig an electric fan that comes on at highway speeds is doing nothing except consuming power it does not aid the cooling. Ram air cools the radiator at speeds over about 40kph.

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Ian Slade
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Re: SP250 Thermostat

Post by Ian Slade »

The Daimler SP spares list refers to opening at 173deg F or 96 deg C, so the car runs fairly hot, the original was a bellows type rather than the later spring and wax which became popular in the 70's.
Depending on the efficiency of your fan in conjunction with the radiator it is sometimes prudent to start the fan manually when entering heavy slow speed traffic so as to stop the temperature rising too high as the pump only runs at about 1000rpm at idle. The radiator is I think borderline in its cooling capability especially when high rpm is used and top gear is not available. (Enjoying high speed mountain pass climbs)
Owner since the 70's, Genghis is slightly to my left.

Crossley Stephenson
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Re: SP250 Thermostat

Post by Crossley Stephenson »

Ian,

I think you will find 173F is about 78C.

Cheers
Michael

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Ian Slade
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Re: SP250 Thermostat

Post by Ian Slade »

Mpringle wrote:Ian,

I think you will find 173F is about 78C.

Cheers
Michael
Yes, sorry schoolboy error regarding the -32
Owner since the 70's, Genghis is slightly to my left.

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