Electric pre heating

I know that people who live in really, really cold places need pre-heating to safely start their cars when it is extremely cold.

I live in a temperate place, but 0C is common on a winter morning. The V12 starts with no problem in these moderate temps, but takes about 10 miles to reach operating temp.

When you think about the energy needed to heat up 300kg of aluminium and 20L of coolant - its about 30Mj. That’s more than a litre of petrol.

What about a bit of electric pre-heating? A stick on sump pad or something? Is it worthwhile?

G’day Russell,

There is an alternative bottom radiator hose available with a heater in it. P/Ns are Hose MNA4512CD Heater EAC9587. These numbers are for the 1995 and on V12s and I’m not sure which car you have.


mines older (part nos c36996, c7205)

first question is - is it worthwhile?

second question- is that passive radiator hose heater the best solution? it heats the block by convection via the (obv stationary) water pump.

G’day Russell,

It sounds like you don’t live in a really really cold climate so it might be of doubtful benefit.

My car comes up to temperature in around 4 kilometres, even in winter, so if your car takes a lot longer may be you have a problem with your cooling system, perhaps a thermostat stuck open.

Next time you start a cold engine check to see whether both sides of the motor heat up at the same rate, feel them.


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Cars in Alaska when I was there back the 80s had a heater element in the oil sump. Kept the oil warm. Anti-freeze kept the coolant as a liquid. Enabled start-up in freezing weather. Kept cars “plugged in” when sitting overnight or more than couple hours. Even the hotels had plug in points for every spot in the parking lot

Thanks Jeff
I’ll check next trip.

The carburettored v12 units had an optional 120v heater element sitting n the water fitting on the face of the water pump. That would have offered heating via convection. Take a look in the 1974 etype parts manual and whether the same item fits the angled inlet housing on the later v12 models.

kind regards

Thanks Marek- I can see those parts (there is also a 240v solution).

I’m doubtful if that is in fact the best solution if one did want to pre-heat.

My main question is whether there is in fact benefit in going to the trouble in a moderately cold place

For my own part, ill also follow up on Jeffs advice to check the thermostat operation

some facelift V12 cars had a lower coolant hose incorporating a heating resistor.
a friend had this on his US market convertible, and removed it when renewing all hoses

hot coolant would rise by convection, and be replaced by cold(er) one, but not sure how it cold go in the radiator without the water pump running

a stickon patch is very little job to install, just need to tidy the wiring , as you dont want a 240V line shorting in the engine bay, and a BIG card reminding to unplug it before moving the car

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It wasn’t me (your friend) but I did have the aux heater too.


In my Canadian location everything we operate in the winter has a “Block” heater. Some vehicles not only have the coolant heater but also a “Strap” heater on the oil pan to preheat the oil as well and this is the combination I use on my Diesel tractor.
Our XJS has the factory coolant heater installed in the lower rad hose but other then to test it I have never needed to plug it in as the car is stored in the winter. The bonus of the heater install in the XJS is it makes a convenient location to drain the anti freeze.
I have never heard of anyone using the winter heaters to preheat in above freezing conditions.

I see very little benefit of preheating the coolant in temperatures well above freezing and using the electric heater in summer conditions would definitely shorten its life expectancy.