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Originally Posted by LeaUK
Most cars I've ever owned take 10 minutes to reach operating temperature, none heat in 2 minutes. In cold weather the driver has also got the heating system running so it's not a closed system then.
I agree that slow heating is often due to the tstat but in my opinion the tstat is completely unrelated to normal operating temperature once the engine has reached thermal equilibrium, unless it's stuck closed/partially which will increase coolant temp above normal - are you sure your W140 is opening fully?
Lea
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Originally Posted by pberku
<85c When the coolant is <85C, the thermostat is in the bypass mode, In this mode, in order to speed-up engine temperature rise as well as for quicker heating ability of the car's heater, the thermostat prevents any coolant from flowing through the Radiator, and diverts all coolant flow towards the car's heater. Under these conditions, the Climate Control Unit, (when set to "AUT") will not turn the Heater fan on until the coolant temperature reaches a pre-set minimum temperature.
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the tstat with this current version, I did test it and it did fully open. Of course, it's been in the car for a few years but the engine temp operates the same as it did the first day the tstat was replaced.
I think that you DO need to check that tstat - - and - - need to make those laser temperature measurements. That's two jobs now
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Originally Posted by LeaUK
I'm soon to purchase a brand new shiny Sachs vfc, so I'll take some measurements before and after fitting and let you know what I find.
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Why are you doing that? You just told me that your current vfc was working perfectly . . "
As I mentioned, it operates to MB spec. This means when unlocked the fan follows engine speed /2. When locked (I haven't measured the temp. of the rad), it follows engine speed until >=approx. 3000rpm when it releases. Then will lock again under around 1500rpm. Now, I just guess that mine is slightly under the minimum tolerance (opening at around 85C)".
That's sounds close to perfect to me; why spend the money for a new one?