Oil leaks are bad news, and not just because they can make a mess on your garage floor or driveway. Oil attacks the rubber used in hoses and belts and could lead to an expensive failure if not addressed promptly. Here we’ll discuss a common BMW repair, fixing an oil leak from the oil filter housing.
How Do You Know You’ve Got an Oil Leak?
If you start seeing oil on the ground or the oil level warning light comes on the oil has been leaking for a while. Before things get to that stage you might notice a burning smell when the engine’s hot. If you’re in the habit of lifting the hood you may also spot oil leaking from the oil filter housing.
Finding the Housing
On inline six-cylinder engines like the N54 and N55 found in models like the F30 335i this is on top of the engine at the front. (Look for the big black plastic cap.) If you’ve got an oil filter housing gasket leaking you may see oil seeping from where the housing meets the cylinder head. It might also be on the black rubber coolant hose that runs underneath.
What Causes a BMW Oil Leak Like This?
Gaskets like those used in the oil filter housing are molded from soft rubber. This compresses when squeezed between two metal surfaces and takes up any microscopic irregularities. As the engine gets hot and parts expand, elasticity in the gasket keeps the joint sealed.
Over time the rubber in this gasket gets hard and loses its ability to seal the joint. When that happens it starts leaking and replacement of the gasket is the only option.
Replacing a Leaking BMW Oil Filter Housing Gasket
As with every BMW repair, the size of the job depends on exactly what model car and engine you have. In general terms though, the job goes like this:
- Remove some of the engine coolant (because you’ll be taking off a hose and don’t want to make a big mess)
- Remove the engine cover
- Remove the intake manifold
- Disconnect the oil cooler lines
- Take the oil cooler housing off the filter housing. (There’s a gasket between these two. While it might not be leaking now this is a good time to replace it because gaskets are not very expensive.)
- Pull the oil filter housing from the cylinder head
- Remove the two gaskets and clean all the surfaces thoroughly. (Forget to clean and you’ll be doing the job again very soon!)
- Replace the ‘O’ rings on the oil cooler lines, (for the same reason — they’re not expensive.)
- Reassemble the filter housing and mount it back on the engine. Note that the bolts are aluminum and stretch when torqued down. It’s prudent to replace them.
- Put everything else back — intake manifold, oil lines, coolant hose and cover — and top up the coolant
When we’ve done a BMW repair like this we always finish by bringing the engine up to temperature and checking carefully for any signs of a gasket leak.
Ask Us About Repairing BMW Oil Leaks
As explained here, gaskets will tend to leak as they age. Gaskets themselves aren’t expensive but getting to them can be a challenge when other engine components need moving out the way. That’s not a reason for delaying replacement though: it’s always best to fix a small problem before it becomes a big one!