Do you see coolant on the ground where you park your BMW? Do you smell something unusual coming from the engine compartment after a drive? Is it normal for the coolant level to keep getting lower? Is your car suffering from an overheating condition? If you are unsure if your BMW is leaking coolant, keep reading to find out how to identify the problem and what to do next.
The most common places for your BMW to leak coolant are the radiator, coolant reservoir cap, water pump, thermostat housing, and radiator hoses.
Continue reading for problematic areas where coolant leaks on BMWs often occur and likely causes.
5 Signs Your BMW Is Leaking Coolant
There are multiple places where you could be losing coolant in your BMW. It could be from a failed cooling system component, faulty coolant reservoir cap, or something more severe like a failed head gasket. Read below for more in-depth information on these problem areas.
1. Coolant Leaking From The Radiator
The radiator on your BMW sits in the front of your car, ahead of the engine, and just behind your bumper. Radiators have multiple passages of metal hoses that the coolant travels through to lower the fluid’s temperature. Most BMW radiators also have plastic end tanks attached on both sides. Due to the changing temperature of your coolant, it will expand and contract the parts of the radiator very slightly. Temperature changes can cause the metal and plastic parts to separate, causing a leak. Sometimes the radiator will only leak when it’s at ambient temperature or when it reaches running temperature, while other times, it could always leak.
Another common cause is road debris hitting the radiator and causing a leak where the damage occurred. If you are involved in a front-end collision, even a minor one with very little damage, the integrity of the radiator can become compromised and cause a leak.
2. A Failed Coolant Reservoir Cap
Most BMW vehicles have a coolant reservoir attached in a remote location under the hood. These reservoirs are sealed using a twist-off spring-loaded cap. Over time and through use, the internal spring can wear out. This means the cap can no longer hold the increasing pressure from the coolant as the temperature rises. Another reason that coolant could be leaking from the reservoir is an improperly installed cap, it might appear to be tight, but if it was cross-threaded, it could leak as the pressure in the system rises.
3. Coolant Leaking From The Water Pump
Depending on the year and model of BMW you own, you should plan on replacing the water pump around the 80,000-mile mark. When your water pump begins failing, it can cause coolant to leak out of it. A belt or chain drives the water pump, and an internal impeller rotates while the vehicle runs. Just like all moving parts, wear and tear from regular driving can cause your water pump to fail.
4. Leaking From Your Thermostat
Most BMWs have a housing made of plastic where the thermostat resides. This housing is bolted to the engine assembly with a seal in it. The heat from your engine can cause this plastic housing to warp, resulting in a leak when the cooling system is under pressure. Another point of failure is the internal seal. These seals can become dry and brittle over time, making them unable to hold pressure anymore.
5. Leaking From Your Cooling Hoses
Since these hoses are made of rubber, they will degrade over time and become dry and brittle from heat and exposure to the elements. When they stop expanding and contracting like intended, they can split open or develop pin-sized holes in them. In most cases, your radiator hoses should be replaced every 4 to 5 years or 50,000 to 60,000 miles. Some radiator hoses will be at the very bottom of the engine bay. These lower hoses can be damaged by road debris or even from pulling into a parking spot too far and making contact with the curb.
Other Cooling System Issues
Head Gasket Failure
When the head gasket fails on your BMW, you might not see any leaks, but you will keep losing coolant. The coolant can leak into the engine and burn during combustion. You may see excessive white smoke coming from your tailpipe. Head gasket failure is a severe problem that needs to be addressed immediately, or you risk complete engine failure. Replacing an entire engine assembly in a BMW is one of the most expensive repairs, so it is best to avoid it!
If the coolant temperature gets too high, it can cause damage to your BMW engine. This could be happening because too much coolant has leaked out, and there isn’t enough left to cool the engine properly. You may see a warning light appear on your dashboard. In some cases, your engine computer may notice this overheating problem and reduce engine performance or shut the engine down to prevent further damage.
There are a multitude of places where coolant can leak from your BMW. The most common are; the radiator, coolant reservoir cap, water pump, thermostat housing, and radiator hoses. You might notice coolant spots where you park your car or smell a sweet aroma. You also might see a warning light about coolant temperature on your dashboard.
Keeping up to date with regular cooling system maintenance and replacing parts at the recommended time or mileage will give your BMW a better chance of running for years to come. Going to a mechanic who specializes in BMW maintenance and repair is the best way to ensure your car is taken care of properly!