Cold Engine Start: How Bad Is It?

Hi, I'd like to know what the diesel experts think. I know that putting too much strain on the engine right after a cold start isn't good, but at what point is it okay to use a little bit of power? I often need to accelerate quickly onto the highway, and in the winter when it's cold, the temperature gauge shows around 50/60 degrees Celsius. The engine reaches that temperature after about 3-4 minutes, or roughly 3-5 kilometers, depending on the route. So, the auxiliary heater is quite effective. Can I already demand some power at that point, or will it definitely damage the engine? It also has something to do with the oil, and 0w-30 is quite fluid.
I'm asking this because I was considering retrofitting a parking heater, but I find it very expensive. It's not about the scratching, but only about the engine. I hope you can help me.
Thank you.

I'm not saying I always want to drive at full throttle, but sometimes it might happen, especially when you're already driving at a fairly fast pace. By the way, it's a 2.0 TDI engine. How susceptible are these engines to that kind of driving, or what might break if it happens?

Best regards,

Hello,

"Kaltheizen" primarily affects the cylinder head. This can lead to premature failure (80,000 km instead of 300,000 km). However, it can also last longer. Cylinder seizing is usually only observed with extreme misuse (immediately revving to full throttle when cold).

It always comes down to the potential lifespan, but how long something will actually last in a specific case is often difficult to predict.

Best regards,
Christian.

@eschmitt:

What chris11 wrote is completely correct. If you put a cold engine under heavy load immediately, the cylinder head will heat up much faster than the engine block. In extreme cases, this can lead to temperature stresses and cracking (due to a large temperature gradient between the intake and exhaust ports). In any case, the head gasket will be subjected to significant shear stress because the cylinder head expands much more than the engine block due to the faster heating and the larger coefficient of thermal expansion. This creates a strong shear load on the gasket in the sealing gap, which is superimposed on the regular load caused by the cylinder pressure.
Furthermore, the oil additives are not fully effective below a temperature of approximately 60°C, which means the oil film cannot be fully utilized. A particular problem is high rotational speeds, which can cause the still viscous oil film to tear in the sliding bearings at excessively high relative speeds. In addition, the operating clearances of all bearing fits are designed for operating temperature, and in a cold state, far from optimal load-bearing and sealing conditions exist.
The warm-up phase of machines also proves problematic in other areas of mechanical engineering, as completely different temperature gradients exist between the machine components compared to the operating temperature. For example, if shafts heat up too quickly, it can lead to galling if the shaft heats up much faster than the bearing housing.
The temperature of the turbine wheel could be particularly critical in this situation, as the wheel has a very small thermal capacity relative to the housing. Furthermore, the housing is cooled by the cold engine oil, which maintains the temperature difference.

So, I would try not to rev my cold TDI engine above 2000 RPM, and at most 2500 RPM. Ideally, the load should also remain below 50% to ensure a more even warm-up of the entire engine.

Regards,
Alex.

donalexo wrote:

If you immediately put a cold engine under a heavy load, the cylinder head will heat up much faster than the engine block. In extreme cases, this can lead to temperature stresses and cracking (due to a high temperature gradient between the intake and exhaust ports). However, the head gasket will definitely be subjected to significant shear stress, as the cylinder head expands considerably more than the engine block due to the faster heating and the larger coefficient of thermal expansion. This results in a strong shear load on the gasket in the sealing gap, which is superimposed on the regular load caused by the cylinder pressure.

Hi Alex,

That sounds like a small cabinet of horrors...

Finally, there's the circulating coolant, which not only dissipates heat but also distributes it "evenly" within the engine block.

So, the "cold" from the die casting block is constantly being transferred towards the ZK (presumably a component that heats up faster), which should prevent the temperature difference between the two parts from becoming too large.

Hi Ulf!

The coolant certainly provides a certain degree of balance, facilitating heat transfer from the cylinder head to the engine block. However, the thermal conductivity of cast iron is quite poor, and its specific heat capacity is very high compared to the aluminum cylinder head. There are already very significant differences here.
It's not quite as dramatic as you might have understood.

Regards,
Alex.

I've always wondered: Does the AJM engine in the Golf actually have an electric heater? And what does it heat up – the oil, or the water?
Hi Markus,

Hello,

You can disregard the standard coolant temperature gauge, unless Volkswagen has made a significant change that wasn't expected in the current models. A good indicator of the engine's temperature is the oil temperature; if it's around 80-90°C, you can accelerate. I also drive onto the highway after 3 km in the morning, but in winter, I stay below 110-120 km/h for the first 10 minutes, depending on the car and the outside temperature (although this is mainly to avoid damage to the fuel pump piston when running on biodiesel). After that, the oil will be warm. In summer, it warms up faster, but even then, a 5-minute warm-up period is recommended.

Best regards, Uli.

hi,
Based on what I'm reading here, the reason for a blown head gasket seems to be related to cold starting.
that the expansion of the head and the block occurs at different rates.
Actually, the biggest stressor on the cylinder head gasket is fundamentally the problem of thermal expansion.
Therefore, an engine with an aluminum block and aluminum head should have significant advantages.
Perhaps it might even be possible to control the process so effectively that the defective ZDK (presumably a component) doesn't fail due to thermal expansion.
Could the ZDK even last forever?
Furthermore, wouldn't an aluminum engine be less susceptible to piston seizures or signs of piston seizure?
What do you do if you have a car (with an aluminum engine)?
What could possibly only be at 75°C after 20km (and 40°C after 10km)?
greetings

"In the first few kilometers, I always shift at 2000 RPM. However, the turbo already provides significant boost even during the warm-up phase, so I'm wondering whether it's better to accelerate more gently to 2500 RPM or to shift more quickly with a bit more throttle?"