Astoria Mechanic | Collision Repair | Tolimas Auto Center

BMW Coolant System Leaks and Repair

BMW Coolant System Leaks and Repair

BMW Coolant System leaks are infamous for being expensive to repair. BMW e39 5 Series, e46 3 Series, and e53 X5 models are very popular due to their relative affordability and great German sport sedan handling dynamics. Aside from suspension maintenance one of the most common repairs on them is repairing leaks in the cooling system. These can be costly and time consuming to repair. In this blog post we will discuss why BMW coolant system repairs are costly and time consuming.

In the late 90’s to early 2000’s BMW arguably made and released their best line up of cars. These cars also introduced a series of new inline 6 cylinder engines with variable valve timing and other new technology. Along with these came a new engine cooling system that was mostly made out of plastic. While other makes were still using aluminum thermostat housings and coolant inlet tubes BMW switched everything to plastic for weight savings.

Plastic Expansion Tanks Are Common Leak Points

The new plastic parts did not have the same long life expectancy as their aluminum counterparts so after a few years of use these engine cooling components started showing signs of failure by cracking and leaking. The problem was compounded as the system uses rubber sealing rings in the plastic hoses to seal the system from leaks.

The Rubber O-rings also leak

One top of the plastic cracking as it ages the sealing rings inside the hoses also warp and leak. This problem is compounded further because the engine cooling system is pressurized. Most cars from the same era have cooling system that run on 8 to 16 PSI. On BMW models the coolant system is pressurized to 30-40 PSI. This problem is compounded further as BMW vehicles have a number of rubber hoses inside the engine compartment which are exposed to heat from the manifold and dry out over time thus causing cracking, failure or leaks in those lines too.

Why Cooling System Repairs are expensive on BMW models

With the cooling system having so many points of failure it can quickly turn a small cooling system leak into an expensive repair. For example, if the plastic thermostat housing is leaking then you will also need to replace the hoses that connect to the thermostat as the rubber ring inside the plastic hoses will lose its shape and be unable to seal after disconnecting the hose from the thermostat housing. Mind you that hose leading up to the thermostat housing had no leaks, but disconnecting it will warp the rubber sealing ring inside.

As you might imagine each of these plastic hoses has to be made in specific shapes and to very tight tolerances making these hoses expensive to buy. This is just one example of why cooling system repairs are so expensive on BMW models.

BMW Coolant Leaks pretty much mean you have to replace all components.

In auto repair we try to save our customers money by only replacing worn or failed components. Unfortunately BMW designed their coolant hoses and components to be single life in that disconnecting them causes them to warp and no longer seal. So every related cooling component to the one that failed must all be replaced.

You can try to save money by only replacing the failed cooling system part and reusing the others, but there is a very high probability that once the repair is completed the vehicle will have a new coolant leak.

This is due to the fact that BMW hoses are made of high quality materials but are very thin-walled making them susceptible to “flaring” or warping when disconnected from their fittings. This means it’s best to replace all the components when you attempt this type of repair on your own, as you can easily make things worse if you re-use old parts and make new coolant leaks!

We at Tolima’s Auto Center have vast experience with BMW coolant systems and we take extra steps such as pressure testing the coolant systems after performing the repair. This way we make sure that our customers get their cars back with no more leaks. If you are experiencing a coolant leak and have any questions feel free to contact us.

Call Now ButtonTap to Call