The Most Common BMW N62 540i, 545i, 550i, 650i, 740i, and 750i Engine Problems
BMW's N62 V8 engine was produced from 2001-2010 and is available in four sizes including 3.6L, 4.0L, 4.4L, and 4.8L variants. The 3.6L N62 engine generates 268hp while the largest 4.8L option makes a staggering 362hp. Though these horsepower numbers may not seem overly impressive now days, this was quite an achievement for a naturally aspirated motor in the early-mid 2000's. However, the remarkable performance does not come without cost as the BMW N62 has its fair share of common problems and reliability issues that may lead to costly repairs.
Common N62 Engine Problems
- Valve Stem Seals
- Alternator Bracket/Gasket Oil Leak
- Coolant Transfer Pipe Leak
- Valve Cover & Valve Cover Gasket Oil Leaks
Of course, this is far from an exhaust list of the problems that may occur on the BMW N62 engine. Additionally, simply because it is a common problem does not mean it will indefinitely happen on every N62. The above list of common problems doesn't seem too bad, right? It's only 5 things after all. Unfortunately for the BMW N62, a few of these problems can cost several thousand dollars to fix. Let's dive in and take an in-depth look at each of the common problems.
1) BMW N62 Valve Stem Seals
Right off the bat, we are jumping into a repair that comes with significant costs: N62 valve steam seals. These seals are responsible for preventing oil in the cylinder head from dripping into the combustion chamber. Additionally, valve stem seals control lubrication of the intake and exhaust valves. N62 valve stem seals are made from poor material (we believe Nitrile) which degrades over time and becomes brittle. Eventually the valve stem seals develop cracks, thereby allowing oil to enter the combustion chamber. As the N62 is DOHC V8 there are 32 valve stem seals - quite the possibility for at least one faulty seal. Worn valve stem seals on the N62 may cause the following symptoms:
BMW N62 Valve Stem Seal Symptoms
- Smoking on cold-start
- Smoking on acceleration (after idling)
- Excessive white-blue'ish smoke
- Increased oil consumption
Smoke on a cold start is caused by the residual oil that sits on the heads. Upon starting the engine, the standing oil is pulled into the cylinder causing smoke as they engine burns off the oil. Additionally, as you sit at a red light or let the engine idle for extensive periods of time, the oil similarly pools up around the valve stem seals. Once throttle is applied, the oil drips through the faulty seals causing the exhaust to smoke as the oil burns away. Faulty valve stem seals typically produce excessive amounts of blue'ish-white smoke, which may become worse with time as the seals continue to wear. Of course, as the engine is burning away the oil entering the combustion chambers, the N62 will experience an increase in oil consumption.
N62 Valve Stem Seal Replacement
Valve stem seals are enough of a common problem on the BMW N62 that a company, AGA, developed a specialty tool collection for the job. Their tool set allows you to replace valve stem seals without needing to remove the intake or exhaust camshafts. Prior to the AGA tools, replacing the valve stem seals could run $5,000-$10,000 to have the work done at a shop. Fortunately, since then, the prices at an independent repair shop with the AGA tools have dropped down to the ballpark of $1,800-$3,000.
DIY'ers may see an opportunity to save some big money on their N62, but not so fast! A new AGA tool set for the job runs a cool $1,000. You may consider checking your local area - maybe someone will rent you the tool for a weekend. Of course, you could avoid using the tools and finish the job the lengthier way by removing the camshafts.
While you (or your mechanic) is working on replacing the stem seals there are a few other items that need replacing or should be replaced. These items include:
- Timing Cover Gasket
- Valve Cover Gasket
- Intake Manifold Gasket
- Actuator Seal Set
This is not an exhaustive list and depending on the age/mileage of your BMW N62 there may be some additional parts that you should consider replacing. Save yourself the time and/or labor costs down the road and knock out what you can. Especially when it comes down to things such as gaskets and bolts.
N62 Valve Stem Seals Replacement Cost:
DIY with AGA Tools: ~$300 in parts (valve stem seals, gaskets, and actuator seal set)
DIY without AGA: ~$1300 if you opt to purchase the tool. You may be able to rent one locally for a couple hundred bucks.
Indy Shop: $1,800-$3,000+
Without AGA: Expert
With AGA: Advanced
2) BMW N62 Alternator Bracket/Gasket Oil Leak
Similar to the valve stem seals, the alternator bracket gasket oil leak is a dreaded common problem on the N62. This oil leak can be attributed to a design flaw and the use of a cheap gasket that degrades over time. Over time, the high engine heat causes the gasket to become brittle leading to cracks and oil leaks. Likely the only symptom of an alternator bracket gasket oil leak is physically noticing an oil leak from that area.
N62 Alternator Bracket Gasket Replacement
A quick search will yield nothing but complaints about how much of a pain this replacement is. Although, the good news is, the gasket costs less than $10. This repair on the N62 requires removal of the alternator, unbolting the power steering pump, lifting the engine, and removing the driver side motor mount. All in all, you're looking at 7-10 hours of labor. Due to the extensive labor to get to the gasket, this job can easily come in over $1,000.
Alternator Bracket Gasket Replacement Cost
Indy Shop: $1,000-$1,500+
Intermediate to Advanced
3) BMW N62 Coolant Transfer (Crossover) Pipe Leak
Moving onto, well...yet another highly dreaded common problem on the BMW N62 engine. The coolant transfer pipe leak is almost impossible to believe because it is such as odd issue. This leak is typically caused by front seal on the coolant transfer pipe, which is located under the intake valley pan. The coolant leaks out of the weep hole. Due to its location in the engine it requires removal of the timing cover, timing chain, intake manifold, and cylinder heads. A coolant transfer pipe could take over 40 hours of labor leading to massive costs, however, there are some aftermarket options that significantly reduce the labor and repair costs.
BMW N62 Coolant Transfer Pipe Symptoms
- Coolant leak from weep hole
- Rapid coolant loss
- Low coolant light
N62 Coolant Transfer Pipe Replacement
As stated previously, there are quite a few aftermarket repair options. One option is the BimmerFix Stent, which only requires removal of the N62 water pump. Another option is the AGA collapsible coolant transfer pipe. The collapsible AGA pipe can be expanded into place avoiding the need to remove the cylinder heads or timing chain. This drastically reduces labor and can typically be accomplished, by an experienced mechanic, in roughly 10 hours. In addition to AGA, there are several other brands that offer a similar option to replace the OEM coolant transfer pipe. Depending on the option that is right for you, there are a few items to consider replacing at the same time:
If you opt for the BimmerFix Stent, consider replacing the water pump as preventative maintenance. The water pump must be removed anyways, so there should not be any significant increase in labor costs. For N62's with recently replaced water pumps this can likely be avoided. However, if your water pump has higher mileage, especially 60,000+, it may be worth the cost of the part to knock it out and save on labor. Regardless, you should always replace the water pump gasket.
AGA or Similar Collapsible Coolant Transfer Pipe
While this job is significantly less intensive than the OEM replacement, it is still lengthier and more expensive than the BimmerFix Stent. Though, it may be a better long-term solution. If you opt to go this route, you should also replace or consider replacing:
- Intake manifold gaskets (N62)
- Profile Gaskets (N62TU)
- Water pump gasket
- Water pump
- Engine block rear O-ring
- Water pipe - pump to heater return pipe O-ring
- Water pipe - pump to valley cover cap
- Valley pan cover cap w/ gasket
- Eccentric shaft actuator O-ring - actuator to spacer
- Water pipe for water cooled alternator housing
This list may look slightly intimidating, however, it is worth replacing these parts while you are in there. Many of the parts are inexpensive, and it's best to knock them out and save on labor costs down the road. Similar to above, the water pump can be avoided. However, it cannot hurt to replace, especially if your water pump is 60,000+ miles.
BMW N62 Coolant Transfer Pipe Replacement Cost
BimmerFix Stent: ~$1,000
AGA or Similar: $1,500-$2,500
Coolant Transfer Pipe DIY Difficulty
4) BMW N62 Valve Cover Gasket Oil Leaks
Finally, a problem that is a common on many BMW engines and not confined to mostly the N62. Valve cover gaskets are notorious for developing leaks on BMW engines. Over time, the engines high heat wears down the valve cover gaskets causing cracks and oil leaks. This may not seem a common problem on the N62 since valve covers should be replaced along with the valve stem seal replacement. However, the valve cover gaskets may begin leaking again regardless, and is likely more common for the lucky folks who have avoided the valve stem seal issues.
N62 Valve Cover Gasket Oil Leak Symptoms
- Visible oil leak from valve cover area
- Burning oil smell
- Smoke from valve cover area
N62 Valve Cover Gasket Replacement
We won't go too far into this as valve cover gasket oil leaks are pretty simple and straightforward compared to the previous N62 problems. However, the valve cover gaskets can still be a complicated repair for inexperienced DIY'ers. Consider leaving this one up to an indy shop unless you are knowledgeable and experienced.
Valve Cover Gasket Replacement Cost
Indy Shop: $700-$1,000
Intermediate to Advanced
BMW N62 Overall Reliability
Though the BMW N62 is plagued by some rather frustrating and expensive repairs, they are generally not terribly unreliable engines. The above common problems are certainly not an exhaustive list of anything that can or will go wrong with the N62. However, the engine should not leave you stranded every week. BMW's N62 engine is definitely best suited for those with basic engine knowledge and the willingness to research. Common problems such as the valve stem seals and coolant transfer pipe could cost $5,000+ for each repair. With basic knowledge of the AGA tools and aftermarket options you should be able to avoid being ripped off by the dealership or indy shops.
The N62 is an impressive performance engine with great power and torque for its age. Although, it may not come at a cheap cost. If you're willing to take some cheaper aftermarket routes and spend time researching you will likely find the BMW N62 as a rewarding engine.
What are your thoughts on the BMW N62?