BMW's N52 engine is one of its most successful, and most produced inline-6 engines. The N52 was predominately found in the E90 325i, 328i and 330i, and the E60 525i and 528i models, as well as various others such as the 128i, X1, and Z4 to name a few. The N52 was produced from 2004 up until 2015 when it was replaced by the turbocharged N20 engine. It is the successor to the M54 which was used in various E36, E39 and E46 models.
Given the long production history, BMW was able to perfect many aspects of the engine over the production lifetime. The engine even won top 10 best engines in both 2006 and 2007. However, the N52 still has its fair share of common reliability problems. We're going to address the 7 most frequent engine issues the N52 experiences.
Due to the engine design, the N52 has proved more reliable than it's bigger brother, the N54. Because the N52 doesn't have an HPFP or direct injection, these are two common N54 issues that drivers of the N52 won't have to worry about. We also wrote an N54 engine problems guide you can read to compare the two!
BMW N52 (328i, 528i) Engine Problems
- VANOS failure
- Hydraulic valve adjusters (lifters)
- Water pump and failure
- Thermostat failure
- Valve cover leak
- Oil filter housing gasket/leak
- Rough idling and slow start-up
These are the most common engine problems, outside of these problems the car is very reliable and problem free. However, I will mention one other common, non-engine related issue is the window regulators. This results in the affected window not being to roll up or down. Replacement cost is approx. $500 at a shop for the part plus labor.
1. VANOS Failure
The N52 engine uses BMW's VANOS system, which is a variable valve timing system. The VANOS solenoids are responsible for controlling how much oil flows to the cam gears, which in turn controls the opening and closing of the valves. Understanding VANOS is rather complicated, although you can read our full guide about it here.
Failing VANOS solenoids will result in a loss of power, poor idling, bad fuel economy, trouble starting, and the occasional limp mode.
These solenoids commonly fail every 70,000 miles or so. We recommend replacing them at this interval as they are likely having a negative affect on performance, although you may not know it yet.
Engine Codes for VANOS Failure
- P1520: Camshaft position actuator, exhaust
- P1523: Camshaft position actuator is jammed, exhaust
- P1397: Camshaft position sensor B
- 2A82: Vanos intake solenoid
- 2A87: Vanos exhaust solenoid
The 2A82 and 2A87 codes are for the intake and exhaust solenoids. The solenoids are exactly the same, so you just need to purchase 2 of part #11-36-7-585-425 to replace these.
If you purchase the solenoids from the links above you can use the code "BMWTUNING" to get 5% off.
VANOS Repair Costs: $178 for the solenoids, about $200 in labor if not DIY'ed
DIY Difficulty: Intermediate
2. Hydraulic Valve Adjusters (Lifters) Ticking Issues
Commonly on higher mileage cars (usually 50,000+), drivers will experience an annoying ticking or rattling noise coming from the engine. It is most prevalent during cold weather or on short trips. The ticking noise is caused by the hydraulic valve adjusters, also known as lifters, not getting enough oil to function properly.The lifter ticking noise isn't detrimental to performance or harmful to the engine, but rather it is extremely annoying and more of a nuisance.
The lifters don't get enough oil due to poor design in the lifters and the cylinder head. This is only prevalent in 2008 and earlier models. The designs of the lifters and cylinder head was changed in December of 2008 which fixed this issue.
How to Fix Lifter Ticking Noises
The first route, and free route, to take is to "bleed" the lifters. To do this, drive only the highway for 30-minutes at high RPM's (>4500rpms). Most of the time bleeding the lifters is a temporary fix that may work a few times in a row until a more permanent solution is needed.
The permanent solution is to replace the lifters and the cylinder head with the newly designed post-2008 parts. Unfortunately, I don't think any pre-2009 N52's have any warranty left, so you will be footed with a $2-3k bill to get this issue replaced if it hasn't already been taken care of.
I suppose the third option is to just drive with the ticking noise and put up with it.
Repair Cost: $3k+ at a shop
DIY Difficulty: Very difficult
3. N52 Water Pump Failure
BMW's are infamous for water pump failure, and it is certainly very prevalent on the N52. It's also a frequent problem on the N54...I blew mine at 42k miles, our E60 blew one at 60k miles, and our E90 had a failed one at some point as well.
BMW's use a electric water pump, rather than a traditional water pump. The electric water pumps are made out of plastic, which over time normally begins cracking and corroding. The bearings and impellers are also common parts that fail within the water pump. Water pumps usually fail around the 80k mile mark. We recommend getting a new water pump that has a metal impeller, since we see the impeller being a common cause of failure.
Symptoms of N52 Water Pump Failure
- Engine overheating (even when just idling)
- Leaking coolant
- Steam coming from the radiator
Water Pump Replacement Cost: ~$400 for the pump, $800 with labor included
DIY Difficulty: Intermediate to Difficult
4. Thermostat Failure
Thermostat failure can sometimes be mistaken as water pump failure and vice versa. This is because the water pump and thermostat work in tandem to control engine temperatures.
Automotive thermostats start in a "closed" position, which helps the car reach normal running temperatures faster. The thermostat then gradually "opens" as temperatures rise. When it opens, it forces the hot engine coolant into the radiator to be cooled off, and the water pump pushes the colder coolant from the radiator to the engine.
Thermostats can fail in either of two positions: opened or closed. Failing closed means the car is not cycling cold coolant into the engine, resulting in extremely quick overheating, and potential serious engine damage from running at such high temps. Continuing to run a car with a closed thermostat can result in head gasket failure, radiator cracking, and cracking/failure of other cooling components.
N52 thermostats are built to fail in the open position. Failing in the open position is the most desirable option, as it is the least harmful to the engine. With that being said, it still isn't good for the car.
N52 Thermostat Failure Symptoms
- Engine is overheating quickly, gauge reads in the red quickly (stuck in closed position)
- Engine takes a really long time (20 mins or so) to reach normal running temps (stuck in open position)
- Erratic temperature changes
- Coolant leaking near the thermostat
The thermostat commonly fails along with the water pump. With the thermostat being relative cheap, we recommend replacing it while replacing the water pump as it will save some costs on labor compared to replacing them separately.
Thermostat Replacement Costs: about $70 for the part, and $150-200 in labor
DIY Difficulty: Intermediate
5. Valve Cover Gasket Leak
Like the N54, the N52 engine is plagued by the same common valve cover leakage. The oil leak can be caused by two things: either the valve cover gasket degrading or from the valve cover itself cracking. Since the valve cover is made of plastic, it warps over time from the engine heat and can crack. The result in both is oil leaking into your engine bay and also a build up of oil in the engine.
If your valve cover cracks you will need to replace the cover and the gasket. The best case scenario is only needing to replace the gasket, which is a lot cheaper.
Symptoms of N52 Valve Cover Leak
- Spark plugs covered in oil (usually on the threads of the plug)
- Ignition coils covered in oil
- Low engine oil light coming on
- Oil in the crevices of the engine block, or signs of oil on the head
- Smell of burning oil from the engine, possible engine smoking if its leaking a lot
Unfortunately, leaking valve covers and gaskets are slightly harder to detect compared to other issues since it will not result in any engine codes. You could get a low oil service light, but this likely won't happen unless you have a severe leak. The easiest way to diagnose this problem is to remove the valve cover and see if you see a build up of oil underneath. Also, remove your spark plugs and ignition coils and see if they are coated with oil and if there is standing oil at the bottom of the valves.
N52 Valve Cover Replacement: approx. $40 for the gasket, about $450 for the cover and gasket. This is probably 6-8 hours of labor from a mechanic, so it can get pricey.
BMW N52 Valve Cover - Includes valve cover, gasket, and bolts
BMW N52 Valve Cover Gasket - Gaskets only
DIY Difficulty: Intermediate to difficult
6. Oil Filter Housing Leak
Similar to the valve cover gasket deteriorating over time, this also frequently happens on the oil filter housing gasket. The gasket seals the oil filter housing to the engine block/cylinder head, and is the most common oil leak found in N52 and all N5x engines, along with the one listed above.
All oil leaks are serious, but the oil filter housing leak is the most serious as it can destroy your whole engine if ignored. If your leak becomes big enough, oil will seep all the way down to the serpentine belt, and cover the serpentine belt with oil. Once this happens, it is only inevitable for the belt to slip off. When it slips off, it goes backwards and gets caught by the timing cover, which chews it up, resulting in pieces of the serpentine belt going through the front crank seal and into the engine. This can kill your engine, or best case result in a few thousand dollars of repairs.
N52 Oil Filter Houston Leak Symptoms:
- Conditions similar to the valve cover gasket leak
- Oil dripping underneath the vehicle
- Smell of burnt oil in the engine bay
- Leaking oil on or around the intake manifold
- Oil spots around the front side of the engine
Oil Filter Housing Replacement: about $30 for the gasket, $419 for the housing and gasket, and 1-2 hours of labor, probably $150-200 all in
BMW N52 Oil Filter Housing - Includes housing, gaskets, cap, and filter
BMW N52 Oil Filter Housing Gasket - Gasket only
DIY Difficulty: Intermediate
7. N52 Rough Idling or Misfires
We've heard a lot of people on the forums complaining of rough idling and occasional misfires from the engine. Other common symptoms will be loss of power, slow starts, and bad gas mileage.
While these symptoms are all similar to VANOS solenoid failure, they will not throw an engine code, and the VANOS solenoid will. If you aren't getting an engine code you likely need to replace your spark plugs and ignition coils. On N52 engines, these typically need to be replaced every 30,000-60,000 miles.
Bad Spark Plugs and Ignition Coils Symptoms
- Poor idling, rough idling
- Bad gas mileage
- Slow starting, or issue starting in cold weather
- Loss of power or sluggish performance
DIY Difficulty: Easy