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How one oil leak can cause big issues

how one oil leak can cause big issues

An oil filter housing leak is a common problem that many European car owners face. The housing is located on the engine block and holds the oil filter. It’s responsible for directing the flow of oil through the filter. It (usually) has coolant passages through it to help cool the oil and/or warm up the coolant. When this component begins to leak it can cause a number of issues; including oil contamination of the cooling system, or coolant in the oil. In this blog post, we will explore why an oil filter housing leak can lead to these problems and what you can do to prevent them.

Contamination of the Cooling System

One of the main reasons an oil filter housing leak can contaminate the cooling system is due to the proximity of the two systems. The oil filter housing is located near the coolant passages that run through the engine block. If the gasket that holds the oil filter housing to the block starts to break down, it can mix with the coolant and cause contamination. This is also an issue with some manufacturers who’ve decided to use plastic instead of aluminum for the oil filter housings. They prematurely fail sooner than aluminum housings due to the plastic distorting.

Swelling of the Hoses

Another issue that can arise from an oil filter housing leak is the swelling of the hoses. The hoses that connect the cooling system components can be affected by the oil leak and begin to swell. This happens because the oil can break down the rubber material of the hoses, and cause them to fail. As the hoses swell, they can physically start touching components they aren’t supposed to (causing leaks), or the rubber breaks down enough they simply start leaking from the connections.

Coolant in the Oil

This is something no one wants to hear. (I don’t want to hear oil in the coolant either) simply because of the absolute mess it makes. The amount of time to clean out these components when they mix these fluids together is immense. You have to completely clean the systems out, or recontamination will be the system’s future- and money wasted to try and clean it once again.

containment in oil

Engine damage!

Yes, you’ve heard this correctly. If coolant gets into the engine where the oil is, you have a very high chance of engine damage. We all know oil and water don’t mix. Bearings, metal surfaces and components that are supposed to be lubricated with oil suddenly are subjected to moisture, rust, lack of lubrication and chemical reactions from the oil and water mix.

Wait, it gets worse?

Yes! BMW’s have an oil filter housing that is directly over the engine drive belt. Follow me on this little story, as we’ve been lambasted by clients who have told us we’re lying, and there’s no way the belt wound up inside the engine….. so here’s how that happens.
Oil leaks onto the belt from the oil filter housing. The belt gets contaminated (just like rubber hoses) and swells up. The belt gets knocked off the pullies and engine, and gets wrapped up in the front of the engine. The shape and design of the harmonic balancer wedges the belt into the front of the engine and forces it through the front seal. The timing chain inside the engine is directly behind the seal and acts like hungry-hungry hippos and pulls the belt inside the engine and chops it up like a blender. These chunks of finely chopped swollen up belt material clogs up the oil pump pick up screen and stops the flow of oil in the engine, causing catastrophic engine damage. You wouldn’t believe it unless you’ve seen it. And you wouldn’t believe the unfortunate conversation of “I told you so” when thousands of dollars in repairs could’ve been avoided by listening to your automotive shop….But we’ve seen it more times than we’d like.

Belt material in oil pan BMW 2009 335i

How do I prevent this?

Maintaining your vehicle at an independent shop. A shop like ours always gives an inspection to your vehicle during routine maintenance. If we suspect or find that an oil leak is present, you’ll be presented with a solution to repair it. This is something that quick lube centers do not do. They simply do what is instructed (put the wrong oil and filter in your car. Yes, I’m serious about this.) but do not do complete inspections to your vehicle, nor give you the information you need and deserve. You deserve an inspection of your vehicle by a qualified technician to tell you what your vehicle needs. Come by, we’ll take a peek and avoid these ugly conversations.


Alex Noll

CEO – ABR Houston

Your Local Experts in Audi, BMW, Mini, Rolls-Royce & Volkswagen Service In The Woodlands.

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