Still Overheating After a Coolant Top-Up? A Guide to Degassing Trapped Air | MyMechanic
You noticed your coolant was low, you did the right thing and topped it up, but now your car is still overheating—maybe even worse than before. This confusing situation is a common problem for drivers in Malaysia and is almost always caused by trapped air in the cooling system.
This guide explains why it happens and how to properly "bleed" or "degas" the system on the roadside. For Singaporean drivers who prefer a professional touch, MyMechanic is equipped to handle these issues correctly and safely.
Why Trapped Air is a Serious Problem
Your car's cooling system is designed to be a closed, liquid-filled circuit. Coolant is excellent at absorbing and transferring heat, but air is not. When an air pocket, or "airlock," gets trapped in a high point of the system (like the thermostat housing or heater core), it acts like a blockage. Coolant can't flow past it, leading to dangerous hot spots inside your engine, even if the temperature gauge is fluctuating wildly.
The Roadside Bleeding Procedure: Getting the Air Out
This process should be done carefully to avoid burns. It works by letting the engine's water pump push the air out through the highest point, which is usually the radiator cap opening.
Preparation:
Park on a level surface. If possible, parking uphill can help air move towards the radiator.
Make sure the engine is cool to the touch before you start.
Have extra coolant/water mixture ready.
Step-by-Step Guide:
1. Open the Radiator Cap: With the engine cool, remove the radiator cap (not the reservoir/overflow tank cap, unless that is the only cap).
2. Turn Heater to Full: Turn your car’s heater to the maximum heat setting and the fan on low. This opens the valve to the heater core, allowing any air trapped there to be purged.
3. Start the Engine: Start the car and let it idle. Keep the radiator cap off.
4. Watch and Wait: As the engine warms up and the thermostat opens, you will see the coolant level drop and bubbles start to come up through the radiator opening. This is the trapped air escaping.
5. Top Up as Needed: As the level drops, keep adding your coolant/water mixture to keep the radiator full.
6. Squeeze the Hose: Carefully squeeze the large upper radiator hose in a pumping motion. This manually helps to push air pockets and coolant through the system. You will likely see more bubbles emerge.
7. Continue Until Bubbles Stop: Keep the engine running until it reaches operating temperature (the radiator fan may cycle on) and you no longer see any significant bubbles. The coolant level should be stable.
8. Cap and Check: Carefully replace the radiator cap. Let the car run for a few more minutes and watch the temperature gauge to ensure it remains stable. Check the coolant level in the overflow reservoir and top it up to the correct mark.
When to Call a Professional
While this procedure is effective, some situations warrant calling for help:
If the car continues to overheat after you've bled the system, you may have a more serious issue like a bad water pump, a stuck thermostat, or a leak you haven't found.
Some modern cars have complex cooling systems with specific bleeder screws that are hard to access on the roadside.
If you are not comfortable working around a running engine or hot coolant.
Cooling System Problems in Malaysia? MyMechanic Gets It Right.
Don't let trapped air cause permanent engine damage. For Singaporean drivers in Malaysia, MyMechanic offers expert roadside assistance to correctly diagnose and resolve cooling system issues, from simple bleeding to complex repairs. We ensure your car is safe and reliable for the journey ahead.
Knowing how to bleed trapped air from your cooling system is a crucial piece of automotive knowledge. It can prevent a simple coolant top-up from turning into a major overheating headache. For Singaporean drivers traveling in Malaysia, being able to perform this check provides confidence. But when the problem persists, knowing you have a reliable expert to call is the ultimate peace of mind. MyMechanic is your partner on the road, ready to handle any cooling system challenge.
