E46 318i Touring: Replacing leaky Oil Cooler gasket [N42]

After fixing the major oil leak from the rocker-cover gasket [THIS POST], I noticed there was still some oil pooling on the under-tray and a fews spots dripping onto the road. I traced the source up the right side of the engine (looking from the front) and could see oil filling up some cavities in the cylinder-head to the left of the oil-cooler / filter housing, so determined this to be the culprit... yes, another common one, especially if the filter-housing has been removed for previous engine work.

A replacement gasket was just £6.59 from eBay and comes as a two piece set including the main gasket that sits between the housing and the cylinder-head, as well as a smaller gasket that sits between the oil-filter housing and the coolant fed heat-exchanger. This latter one hardly ever leaks, as it's very rare to find a filter-housing that has been split apart during engine work, but it's nice to have one anyway and you may find it worth the time to replace this one while the housing is removed, though I could not see any signs of leakage so didn't bother.

GUIDE:

1. Remove the lid to the air-con ducting that sits atop the firewall at the back of the engine by undoing the clips a quarter-turn, take out the pollen-filter and remove the weather-strip seal from the firewall.

2. Remove the air-con ducting itself by undoing the four screws using a T30-Torx socket and lifting it out.

3. Remove the rear right-side engine cover by undoing the two stud-nuts using a 10mm wrench.\

** Make sure you have a cloth / plenty of tissue to catch any oil that runs from the housing. **

4. Remove the three screws holding the oil-filter / cooler housing to the cylinder-head using a 10mm socket with a long extension bar. One is clearly visible in front of the housing, the other two being hidden down the back.

5. Lift the oil-filter / cooler housing upwards out of the head, catching any wayward oil and lift the housing clear, rotating it so as not to put too much strain on the coolant-hoses. The hoses do not need removing or any coolant draining for this job.

6. Remove the old gasket and clean both mating surfaces with a cloth and I find it always worth scraping any crud off with a razor-blade.

7. Insert the new gasket to the housing. A lug on one side sits in a notch in the housing so the gasket can only fit in one way. [If it's an older engine or the housing has been removed a few times before, it might be worth taking a belts-and-braces approach by applying some gasket sealant to the mating surface on the head, as I did with some white Corteco.]

8. Carefully place the filter/cooler housing back onto the cylinder-head, trying to spill as little oil as possible on the mating surface and reverse steps 4-1 to refit.

E46 318i Touring: Oil leak fixed! Rubber rocker-cover gasket was the culprit!

It's about time I got back to wrenching on some Beemers after a busy hiatus, so where better to start than with the massive oil-leak on my E46 318i Touring. The car hasn't seen much use over the winter months, but as I start to need it again for its cavernous load-lugging functions, I figured it was time to spend a bit more time getting it right.

I was going through about a cupful of oil every 100 miles or so (I think that is a pretty favourable estimate to be honest, more like half a litre!) and worse than the cost of all the topping-up, smoke continued to billow from not only the sides of the bonnet (hood) while stopped at traffic-lights, but also straight into the cabin with the blowers turned on. This meant for the last 12 months I have had the climate-control set to full recirculation mode and on low, making de-misting the windscreen a nightmare on colder days.

I could see the oil-leak was coming from the rear left side of the engine, as it so often the case with N42 engines and assumed it to be the vacuum-pump (like with my E46 318ci in this this post), but after removing the rocker-cover (cam-cover) I found it was actually the rubber gasket itself. The thick rubber gaskets tend to harden and go brittle over time and almost completely down the left side of the cam-cover there was noticeable leakage, primarily at the back corner, next to the vac-pump of course. The gap at the rear-left corner was so pronounced I feel you could have slipped a credit-card through with a little force and touched the back of the cam-shaft! This was allowing a constant drip of oil out onto the heat-shield and down onto the exhaust-manifold, as shown by the arrows in the picture and causing most, if not all of the smoke.

Luckily, I suppose, I have been working through the Covid epidemic, so I am classed as a 'key worker' and had a day off, so I managed to blag Euro Car Parts that it was essential work and instantly collect the new Elring gasket (£22, but eBay alternatives are as cheap as £9.50 if you can wait!) and some Corteco White instant gasket-sealant (£7), though they still had me waiting for an hour outside!

Knowing how prone the top-end seals of the N42 are to leaks and not wanting to take any chances of removing the rocker-cover again anytime soon, I slapped on a liberal bead of the Corteco sealant over the vacuum-pump ring and along the entire left-side (lower) surface of the cylinder-head top edge along with the new rubber-gasket. The job does not take long at all (I will post a guide soon), with removal and refitting of the cam-cover only taking around 30 minutes each and that's taking your time...

Needless to say, this has stopped the major part of my oil-leak in this area! Not only has the oily steam stopped from the sides of the bonnet while stationary, the smell/smoke from the climate vents has now ceased and the car is no longer consuming oil at a silly rate, so I would say job done! There is still a tiny weep of fresh oil coming from around this area, but nowhere near like before and, after a run where the engine is warm, there is no dripping pool on the under-tray! For the money I spent, the difference in convenience is worth vastly more! I would have spent the ~£30 I did in oil in a couple of weeks using the car daily, so if you have this problem, it's safe to say this is the culprit and get it sorted!