From owning my 2007 BMW N54 335i and working on other N54's, I've compiled a road map of sorts listing maintenance items and average mileage change. The N54 is a solid motor and can take quite a bit of abuse, but to keep enjoying it, you'll need to stay on top of the maintenance. The easiest way to keep the maintenance is to go by mileage up to 100k. Since in the eyes of BMW, 100k miles is the end of the car's lifecycle.
An N54 powered vehicle requires a lot of attention, and when something needs to be changed, it will need to be changed quite soon. Since letting it fester will yield an even bigger issue. Take, for instance, the oil filter housing gaskets. Once they start to leak, you risk running the motor low on oil which can cause you to spin a bearing and yield your car inoperable, or soak your accessory belt and tensioner with oil, requiring it to be changed.
This blog is not a bible of sorts but a recommendation of my current maintenance schedule. Also, since there are different stages of the BMW 335i, which segments from motor and turbo setup, I've purposely excluded items outside of the function of the motor, such as the transmission, differential, and suspension components.
If you have any suggestions etc., please feel free to comment below.
Every ~8k Miles
- Oil Change & Oil Filter
- The oil change frequency depends on how hard you drive. I like to stick to around the 5k mark since I do about 80% normal cruising, and the other 20% doing a few pulls here and there.
- A good investment is in a billet oil filter cap, in which you replace the OEM one, which has the vulnerability of possibly cracking.
- Since I'm in Florida, the weather is quite sunny and hot, so I run a 5W40 weight oil. The BMW N54 engine runs hot already and, combined with the high ambient temperatures, the 40 weighted oil. In colder climates, an OW40 oil is more ideal.
Every ~25k Miles
- Spark Plugs
- If you're not going to use the OEM Bosch spark plugs, and use any of the NGK colder plugs, make sure to gap them correctly, or you will have drivability issues.
- Stock to ~440 WHP - Bosch ZGR6STE2 - Stock
- Stock to ~550 WHP - NGK 95770 - One step colder from stock
- 550+ WHP - NGK 97506 - Two step colder from stock
- Walnut Blast
- The intake tract gets quite gunked up because of the nature of direct port injection engines. Having the engine walnut blasted frees up horsepower and provides an efficiently running engine. But make sure whoever is doing this procedure has done it before and is knowledgeable about the N54 engine since such a straightforward procedure can cause your motor to blow.
Every ~50k Miles
- Coil Packs
- Cabin Air Filter
- Engine Air Filter
Every ~75k Miles
- Injectors and decouplers
- The last revision of the BMW N54 Piezo injector is index 12. If your motor has any of the earlier versions, make sure to update them to index 12. From the entire list, this is one of the most expensive parts to replace. But it's vital since driving on a leaky injector will dilute your oil and put your motor at risk. It is usually ending with a spun bearing.
- Oil Filter Housing Gasket
- Oil Pan Gasket & Bolts
- The oil pan gasket is a cheap gasket to obtain; the problem is you have to lower the subframe to replace it. It's quite straightforward but will take you a better part of the day to complete. Also, some of your oil pan gasket bolts might snap just by touching them. Just be mindful you might need a reverse bit to extract it.
- Valve Cover and Gasket
- The OEM valve cover is susceptible to cracking and leaking. For N54 powered cars equipped with top mount single turbos, a good upgrade is an aluminum valve cover.
- Cooling System
- Water Pump
- The OEM Waterpump has a plastic outer housing, and either it will crack and leak from that location, or the internal propeller will fail. You can upgrade and get a Pieburg built Waterpump, which has an aluminum outer housing. The OEM pump generally lasts between 80k to 110k miles. Anything over that and your driving on borrowed time, make sure your AAA membership is up to date.
- Upgrade to CSF Aluminum Radiator will eliminate this to-do item. The OEM unit has plastic end tanks that leak or break entirely especially the upper radiator hose connection.
- Coolant Reservoir
- Upgrade to a Tuner aluminum expansion tank. It will replace your plastic unit, which will crack or even lose pressure by the seals.
- Radiator Hoses
- The most crucial coolant hose that needs to be replaced and is more than likely to crack while sitting in traffic is the coolant vent hose, which connects from the coolant reservoir to the upper radiator hose. The ends are rubber, but BMW said, you know what would be great for some reason. Let's add plastic in between the rubber.
- Use Genuine BMW coolant mixed with distilled water. If you can't get your hands on the BMW coolant, then make sure the one you purchase doesn't contain Phosphate and Nitrates. The last to you want to do is gunk up the engines coolant passages and reduce coolant flow.
- At 100k miles, this is an excellent time to upgrade to a single turbo setup. If your already single turbo, it's a great time to check your connection and check for shaft play and leaks. You can upgrade to twins, but down the line, you will spend money again and end up single in the long run.
- Vacuum Lines
Every ~100k Miles
- Accessory Belt and Tensioner
- Vanos Solenoids
- High-Pressure Fuel Pump