Technical cold starting in very low ambient temperature after Coolant changing

[jenna3000]

in the book why does it say

cold starting in very low ambient temperature

Do not warm the engine by letting it idle for a long time. Start driving immediately at moderate ebgine speeds 2000-2500rpm to warm up the engine properly.

after the coolant is changed should it be revved at 2000-2500rpm

 

[Reg 65]

Engine wear is greater when the engine is cold (oil circulation etc) so the idea is to get it to operating temperature as soon as possible.
Oil works like a skier being towed over a shallow pool. The faster you go the less he will be scraping the bottom and causing wear. So you can very easily be causing more wear on tickover than at 2,000 rpm. The faster he is going the better the water (or oil) works in keeping the moving parts separated and reducing friction and wear. if you stop he sinks to the bottom, and you have to brute force drag him along scraping the bottom till he is going fast enough to lift off the bottom again. This is why start/stop is so wearing. Every time you stop you are likely to get metal to metal contact until you get up to speed again. You are more likely to get metal to metal contact at low speed, than at normal speed. Especially since the oil pressure is lower.

Also with changing the coolant you need to circulate it vigorously to get rid of the air bubbles before voids cause localised overheating.
There is nothing is the service schedule about changing the coolant in my X2/50 or X2/90. Its not the antifreeze that wears out its the corrosion inhibitor - and the time that takes depends on the type of coolant and the metals used in the engine, Which the vehicle manufacturer knows and the coolant manufacturer doesn't - so take the advice of the vehicle manufacturer over the coolant manufacturer.
Because of the potential damage caused by air bubble voids and localised overheating its very easy to do more harm than good by changing the coolant. Especially if you don't know how to bleed the system

 

[Anthony489]

Hi

The advice to drive off reasonably promptly rather than letting the engine idle is fairly standard these days. The engine warms up due to waste heat, and since little power is needed to idle an engine there isn't much waste heat being produced, far less than when driving along. In cold weather it could take a very long time to reach normal operating temperature just idling. This is especially the case for diesels, which are more thermally efficient than petrol and produce a smaller proportion of waste heat.

Although radiator fans are thermally controlled these days, and the main thermostat won't allow circulation to the radiator until it's hot enough, coolant is always circulating to the heater matrix in the cab. If you turn up the cab fan speed in an attempt to warm up the interior, this will be sucking heat out of the engine and delaying its warm up still further.

Modern multigrade oils circulate better when cold than in the bad old days, but even so the wear rate is more until the engine is properly warm.