BMW’s 4.4 and 4.8 liter N62 V8 engine was produced from 2002-2010 and was used in a variety of models from their 5,6,7 series to the X5 SUV. It is a naturally aspirated, dual overhead camshaft engine. Although a very reliable engine it is not without its problems.(and some are pretty big) So if you own or plan on purchasing a BMW with this engine be sure to read the rest of this article.
Oil Leaks– Along with the common valve cover gasket leak this engine has a host of other likely suspects. The oil pan gaskets on these engines are known to leak and are quite labor intensive resulting in a high cost to repair. (Fig 1) The gasket that seals the oil pan to the engine block is a metal gasket with a rubber seal formed on the inside. Over time this seal becomes hard and shrinks allowing the oil to get past. Another source of leaks that is common is the alternator bracket gasket. (Fig 2) On engines with an engine oil cooler this is the location on the engine where the oil leaves and returns to the cooler. On engines not equipped with a cooler there is simply a seal in place to route the oil back into the engine. On either model this seal is prone to leak and costly to replace because of the location. At some point this will fail and need to be replaced. The vacuum pumps are known to fail internally and leak oil through the pump unit. (Fig 3) The only issue with this is the oil leak will not be visible in most cases. Most people do not even realize there is a problem until the brake pedal becomes hard to press. When the pump fails internally the oil that leaks out is directed to the brake booster where it proceeds to fill the unit with oil until the unit no longer is able to function resulting in a hard brake pedal. Other common oil leaks include oil pressure sending unit, upper timing chain covers and vanos solenoids.
Valve stem seals– The Achilles heal of this engine seems to be the valve stem seals and guides. The seals are known to leak causing excessive oil consumption, smoke from the exhaust at start up and when idling. In some severe cases I have seen valve damage as a result of not addressing the issue and continuing to drive the vehicle. The seals (like the alternator bracket gasket) are fairly inexpensive but be prepared for a bill in the neighborhood of $3500.00. It is for this reason most people will either ignore the issue or sell the vehicle.
Secondary Air injection (limited to models with N62B44 4.4L engine) – Another common issue with this particular engine is the secondary air injection system. The job of the secondary air injection system is to lower emissions on cold start ups by injecting fresh air. The N62’s main issue with this is that the ports are fairly small and become clogged with carbon which doesn’t allow the air to be introduced. Once the Oxygen sensors pick this up it instantly triggers a pesky <a https://europeanedgeoftallahassee.com="" auto-diagnostics="" "="">check engine light. Some company’s have made kits to clean the passages removing only a minimal amount of components and using a chemical but the only way to truly resolve this issue is by removing the exhaust manifold and drilling out the passages to remove the clog.
Coolant Transfer Pipe– The coolant transfer pipe resides in the lower area of the intake valley. This pipe runs from the front of the engine to the rear and is sealed by 2 large o-rings. Seems fairly simple right? The only problem is that when the o-ring fails the pipe has to be removed and in order to do that the engine has to be removed. Luckily a company designed a replacement pipe that can be installed with the engine in the vehicle. To remove the old one you simply cut the pipe in half and remove the 2 pieces. The new pipe is telescopic and is threaded in the center. You simply screw the pipe apart until it is fully seated and voila! I have installed many of the replacement units and have yet to see one of them fail.
Crankcase Vent Valves- These units help regulate crankcase pressure/vacuum. The diaphragms deteriorate over time due to exposure to oil and heat. Once the diaphragm breaks it allows the intake to pull the oil out of the engine and burn it. Along with the oil burning this also creates non-metered air entering the system which will cause a check engine light and depending on the condition a rough idle. These components are fairly inexpensive and easy to change.
With the exception of these flaws this engine is still a relatively stable platform when maintained. Thanks to the collective effort of BMW believers many of these issues now have fixes and upgrades to correct them. I owned a 5 series with this engine and it was an incredibly fun vehicle to drive and very responsive. Even with these issues I would own another BMW with this engine.