We would like to make you aware of how our mechanics’ thorough training and expertise working with all models of BMW saved one of our valued customers a lot of hassle and a great deal of money. Time spent understanding the theory at college is important but there is no substitute for actual hands-on experience under the bonnet of a car. This develops intuition and some mechanics have almost a sixth sense when it comes to diagnosing problems.

Never Ignore Your BMW’s Dashboard Warning Lights

In recent months, our mechanics have reported a spate of complaints from BMW owners, who have noticed warning lights on the dash indicating either ‘coolant low warning’ or ‘losing coolant warning’. Some have also found worrying physical evidence of oil in the coolant reservoir and a milky substance in the engine oil cap. In a cases like these, it’s always best to avoid risk and seek professional advice ASAP.

You don’t need to be an automotive engineer to know that oil and water don’t mix, and this is never truer than in the case of internal combustion engines. While engine oil is designed to lubricate moving parts and limit wear-and-tear, water is mixed with coolant to regulate a vehicle’s radiator temperature and prevent overheating or freezing. Cross-contamination of these fluids is a potential recipe for disaster and extremely expensive repair bills. Prevention is always better than cure. At BMW Car Service North Shore, we are experts in running diagnostics and completing the most cost-effective repairs for our many satisfied clients.

The Strange Case of the BMW X3

A specific case in point was when a customer who brought a 2012 model BMW X3 with N20 engine in for diagnostics and repair, after becoming aware of similar symptoms to those outlined above. The car had already been to two mechanics, the first of whom flushed and replaced the engine oil no less than three times, using up three new filters and 15 litres of oil in the process without success.

The second mechanic made a completely different diagnosis i.e. substantial engine damage. The quote provided stood at an eye-watering $7,000! This was to include the repair of a suspected cracked cylinder head and blown head gasket. As you will see below, this could well have been wasted money.

Saving a BMW Owner Money Through our Accurate Diagnosis

Luckily, the customer was smart enough to come to us for a third opinion. Our mechanics are highly experienced in BMW engines and suspected a very different issue i.e. a faulty oil filter housing.

The BMW X3 is not the only model in the company’s range to feature the N20 engine, and one thing they have in common is their plastic oil filter housing. This unit serves to protect the oil filter and keep it firmly in place. It is positioned adjacent to the engine and is attached to a metal oil cooler. Within this cooler are two separate sections that act as reservoirs for engine oil and coolant.

It works using a coolant line connected directly to the oil cooler. Coolant flows through one section of the oil cooler, while the engine oil flows through the other. The oil filter housing ensures that oil runs through the oil filter and that coolant is directed via another conduit, to cool the oil without crossing and contaminating it.


Our Mechanic’s BMW Experience Proved Vital

The key to our successful diagnosis was a knowledge and  appreciation of this particular BMW’s service history. It revealed no prior overheating issues (a problem typically caused by the mixing of oil and water). This led our mechanics to deduce that the issue lay within the oil cooler mechanism. This became the starting point for our investigation and saved a great deal of time and money.

Access was gained by removing the intake manifold and other components in the correct order, to reveal the bolts that secure the oil filter housing. This was subsequently removed to allow detailed inspection. Their BMW experience told our mechanics that when oil filter housings warp, it can cause coolant to leak into the oil and vice versa. However, with this BMW X3 they found a different cause, evidence of leaks coming out from the housing itself, due to a crack between the oil and coolant chambers.

This explained why flushing the system three times and replacing the engine oil failed to address the issue. Spending thousands of dollars on a new cylinder head and head gasket would yield similar results, as the problem would have simply recurred, due to the continual leakage and combination of oil and water. Our goal was always an accurate diagnosis and cost-effective repair, which was achieved by replacing the oil filter housing, then flushing and cleaning the entire system.

BMW Coolant Leaks Can Be the Result of Heat Transference

You may want to know which factors caused the BMW X3’s oil filter housing to fail and the oil and water to mix. The simple explanation is age but, technically and more precisely, it’s heat. Everyone drives differently and some owners are heavy on the gas pedal, which can raise the engine temperature. The start-stop of a rush hour commute can have a similar effect and increase wear-and-tear on many components.

These days so many car components are of plastic construction, including valve covers, oil filter housings and even some engine sumps. When summer temperatures soar, the parts can become vulnerable to heat damage, especially with the air conditioning unit on full blast and its condenser working overtime. Once you come to a halt, with your engine running and no airflow, the temperature under the bonnet could easily hit 70-degrees centigrade. Although plastic polymers are designed to expand and contract within certain tolerances, extreme variations can cause plastic housing to compromise and develop permanent cracks, which is probably what happened with the BMW X3.

Oil Filter Housing Replacement

The replacement of the oil filter housing in the BMW X3 was the first step we took to rectify the problem. Once this was done, we carefully flushed the engine and the cooling systems twice. Next, we fitted a friction modifier to the engine, to help prevent water intrusion. If water does gradually seep in between two metal surfaces inside the engine, the materials will corrode and cause serious consequential damage. The friction-proofing our mechanics installed creates a protective coating on all metal surfaces so when they come into contact, it takes a lot more pressure for engine wear to result than with untreated surfaces.

Get BMW Oil Filter Housings Checked Regularly to Avoid Repair Bills

If you are the owner of a BMW X or Z, 1,2,3,4,5 or 6 series, from 2011 onwards, which features the N20, 4- cylinder engine, we recommend you bring it to us as soon as possible, regardless of mileage, so a mechanic can check the oil filter housing.

If your car does a plastic oil filter housing, it is in your best interests to have it replaced before the warning light flashes and the component fails, potentially causing coolant to mix with engine oil in the sump and engine oil to leak into the cooling system. If you wait till the ‘coolant low warning’ or ‘losing coolant warning’ lights come on, it will be too late and the damage will probably already be done. Act now and save thousands of hard-earned dollars further down the line!

Always Insist on Genuine BMW Parts

BMW are fully aware of the oil filter housing issue and have taken steps to replace the plastic component with an aluminium alloy version that can withstand high temperatures while remaining relatively lightweight. Be sure to specify this genuine BMW part when ordering your next service. Damaging leaks should then be a thing of the past.

Click here for more detailed BMW Car Service North Shore information.