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2026
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Been running the car for a while and the water temp is still low?
This summer, Old Wang bought a new car. It ran fine in the summer, with the water temperature neither too high nor too low. But when winter came, even after running the car for more than 10 minutes, the water temperature was still very low, and the heater wouldn't blow warm air, leaving Old Wang shivering from the cold.
"Why does my car's engine temperature rise so slowly in winter?" What problems can a slow-rising engine temperature cause, and what are the reasons behind it? Old Wang, full of questions, once again went to Old Li, seeking help from this expert. Today, let's answer these questions for everyone.
▎ Too high or too low won't do—Engine Temperature
When we talk about 'engine temperature,' we mean the temperature of the engine coolant. Engine coolant helps dissipate heat from the engine. It circulates through the cooling system, carrying excess heat from the engine to the radiator to be 'released,' thereby ensuring the engine stays at an ideal operating temperature.
After the engine is cold-started, it needs to go through a warming-up process, during which the water temperature gradually rises. If the water temperature rises too slowly, it means the engine can't reach its ideal working temperature quickly. This can lead to three problems.
● Poor heating performance
This is also the reason why Old Wang finds it unbearable. Since the heat for the car's heater also comes from the engine's cooling system, and Old Wang's car takes too long for the water temperature to rise in winter, the heater doesn't warm up soon after starting the car. That's why Old Wang has to endure the cold for so long.
● Increased fuel consumption
Before the water temperature reaches the ideal working level, the engine oil is thicker, which makes the engine work harder. As a result, fuel consumption during this time is much higher than normal. Any experienced driver would know that fuel consumption during a cold start in winter is much higher than usual.
If Old Wang's car's water temperature rises slowly, it can make this high fuel consumption process last longer, and overall fuel consumption will also shoot up.
● Increased Engine Wear
Most engine wear comes from the cold start phase because the engine oil is thickest at cold start and doesn’t lubricate well. If the water temperature rises slowly, the oil temperature can’t increase quickly, which prolongs the warm-up period, worsens cold-start wear, and creates a vicious cycle.
▎ Understand the Problem and Address It
Alright, now that we’ve explained the harm, let’s analyze why the water temperature rises slowly.
● Thermostat Malfunction
The main culprit is usually the thermostat. The thermostat is a valve that switches between the engine's small and large circulation loops, and the small loop is meant to let the engine water heat up quickly so the engine can get through the warm-up phase as soon as possible. When the thermostat has issues, it naturally causes the water temperature problem.
If the thermostat can’t open on time, it will cause the water temperature to get too high. On the other hand, if the thermostat opens too early or gets stuck in the open position, the problem is that the water temperature rises slowly. At this point, the engine only has a large circulation, so the water temperature can’t increase quickly. In this case, we need to contact the service station to replace the thermostat as soon as possible.
How to fix it: Replace the thermostat.
● Cooling fan malfunction
The purpose of the cooling fan is to speed up the radiator's heat dissipation and prevent high water temperature. But if the cooling fan works “too hard,” it can actually cause the water temperature to rise slowly. The most common issue is that the fan keeps running constantly, which is usually caused by a problem with the clutch or wiring. You’ll need to contact service station staff to check and repair it.
Solution: Replace the thermostat.
● Water Temperature Sensor Malfunction
If the water temperature sensor malfunctions, the temperature readings will be inaccurate, so the water temperature shown on the dashboard is likely wrong.
For instance, if the water temperature sensor has internal issues or problems with the wiring, like a break or loose connection, it can cause the water temperature gauge to show a lower temperature, giving a false impression that the water temperature is rising slowly or even not increasing at all.
Solution: Replace the water temperature sensor.
▎ Driving Tips to Make Your Ride Enjoyable
After fixing the water temperature issue, here are a few tips to help truck drivers have a more comfortable driving experience in winter.
● Warmth essential — the truck "mask"
As an experienced driver, especially a veteran driver from the north, you surely know that truck thermal covers have a long history. As a winter driving necessity, the thermal cover installed on a truck's front air intake has already become a familiar sight on the roads in northern China during winter.
It might look like just a small insulation cover, and the cost isn't high, but it plays a pretty important role. Back in the days before silicone oil clutch fans became common and when cooling fans were directly connected to the engine, an insulation cover could help the engine warm up quickly after a cold start. It could save fuel, improve the heater performance in the cab, and make driving more comfortable.
Even by 2020, quite a few truckers in northern regions still installed insulation covers on their trucks during winter, and indeed, it can help the engine water warm up faster.
● Take it easy—don’t turn on the heater right away.
When a truck has been parked overnight, the whole vehicle is basically frozen through. At this time, it's not appropriate for drivers to turn on the heater right after starting the engine.
On one hand, the engine hasn’t warmed up properly yet, so the water temperature is low, fuel consumption is high, and you’re basically burning your hard-earned money.
On the other hand, the engine is already cold, and turning on the heater actually slows down the warming process. Plus, the heat coming out at that point won’t be warm anyway. It’s better to stay calm, wait a few minutes, and turn it on once the water temperature rises.
Driving isn’t easy for us truckers, but the vehicle is still just a tool, and occasional issues are inevitable. Understanding some of the basic mechanics makes driving smoother, helps you tackle problems effectively, and avoids wasting money blindly.
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