The 8 Most Common BMW N54 135i, 335i, 535i Engine Problems
The BMW N54 engine might be the best tuner engine of all time…at least we think so. Before we even get started, I’m going to drop a plug for a soon-to-come post on why the N54 engine is better and more tuner friendly than a 2JZ. Hopefully I can get some Toyota fans to read it so we can stir up some drama.
Anyways, back to the point. The N54 engine is one of BMW’s best engines, no doubt. But…that isn’t to say that it doesn’t have any problems of its own. In fact, the N55 engine was slightly dialed back in an attempt to tame some of the common engine problems of the N54. Be sure to read our guide on the N54 vs. N55 if you aren’t sure what the differences are (outside of single turbo vs. twin turbo).
This post is going to cover the most common N54 engine problems, along with the symptoms and error codes to be able to identify them. On top of that, I will cover general maintenance tips to reduce the possibility of these engine problems, as well as repair and replacement options in the case that you fall victim.
Common BMW N54 Engine Problems
These are the most common N54 engine problems:
- High-Pressure Fuel Pump (HPFP) Failure
- Turbocharger Failure / Wastegate Rattle
- Leaky Fuel Injectors
- Leaking Boost / Chargepipe Failure
- Valve Cover Oil Leak
- Carbon Build-up
- Vanos Solenoids (2A87 and 2A88)
- Water Pump Failure
We will touch on all of these in-depth, focusing on the symptoms of each problem, the performance impact, and the repair options.
Woah, that’s a lot of problems…how common are these problems?
If you are in the market for an N54 powered BMW and just read that list, you are probably reconsidering your choice. “Well, maybe an N55 is better”, is likely running through your mind. It definitely did when I was looking for my 135i…but the substantial difference in tune-ability between the N54 and N55 is what brought me back.
My 135i is a 2008 (10 years old already!) with only 32.5k miles on it, meaning it is probably running on 95% straight-from-the-factory parts that are 10 years old too. And my warranty is up. But the truth of the matter is, while some of these problems are inevitable, the majority of them are preventable.
If you drive 125mph for 30-minutes like you are on the Autobahn, yes you will probably bust your N54’s water pump. If you are running 20psi on factory turbochargers, yes you will definitely bust your chargepipe, and probably blow the turbo’s. Read on and we will cover each N54 problem.
1. High Pressure Fuel Pump Failure (HPFP)
You guessed it, the N54 high pressure fuel pump is responsible for injecting fuel into the engine. The HPFP feeds fuel through the injectors, which directly supplies the engine with gasoline necessary for combustion. If your HPFP fails, your engine will not get the fuel it needs to run. Sounds like a big problem? It is.
Unfortunately this is probably the single most common engine problem on N54’s. Fortunately, BMW realized that, and warrantied it for 10 years or 120,000 miles. If you own a higher mileage N54, it is likely that you have had your HPFP replaced at one point in time.
BMW N54 HPFP Failure Symptoms:
- Long crank time (slow engine start)
- Check engine light illuminated
- Car enters limp mode, and runs poorly with decreased power
N54 HPFP Failure CEL Codes:
These are common codes, certain ones might not indicate a failed HPFP (such as a cylinder misfire code)
- P142E: low pressure in HPFP system – injection disables to protect catalytic converters
- 2FBF: Fuel pressure at injection release
- 2FBE: Fuel pressure after motor stop
- 29DC: Cylinder injection switch off
- 29E2: Fuel injection rail
- P030(1-6): cylinder misfire (last digit of code is the cylinder responsible)
Why Does the N54 HPFP Fail?
This is a fantastic question. We asked BMW the same thing – but there doesn’t seem to be a specific reason outside of poor mechanical engineering. BMW did have dealers recall HPFP’s with certain manufacturing codes, which suggests that it might be related to bad manufacturing batches.
Running a tune, such as the JB4 or Cobb, will not increase the chances of your HPFP failing. Nor will any other performance part for that matter. Stock and tuned N54’s have both experienced these issues. Also, there doesn’t seem to be any correlation to a failed pump and how hard you drive the vehicle or whether you have a standard or automatic transmission.
High Pressure Fuel Pump Repair Options & Warranty
I know a mentioned earlier that most of these common issues are preventable. Well, unfortunately this one really isn’t. But I promise most of the others are. HPFP failure seems to be related to the specific pump in your car, and is random in nature.
BMW has warrantied this part for 10 years and 120,000 miles. Hopefully you fall into this warranty. If not you will need to buy the part and have it installed by a mechanic, if you aren’t capable of DIY’ing it.
Replacement HPFP: ~$450 (plus install, don’t go to a dealership)
DIY Difficulty: Advanced
2. Turbocharger Failure & Wastegate Rattle
While the high pressure fuel pump failure might sound like a disaster, Wastegate rattle is by far the worst most common N54 engine problem. Typically, Wastegate rattle requires two brand new turbochargers, which is very expensive if you aren’t still under warranty. Read on to learn the symptoms of Wastegate rattle and learn how to mitigate the chances of it happening to your N54.
What is an N54 Wastegate and Why is it Important?
The Wastegate controls the outflow of exhaust gases away from the turbochargers. This regulates the speed at which the turbo’s spool and generate boost pressure. In simpler terms, the Wastegate controls the maximum boost pressure created by the turbo’s, which protects both the engine and the turbochargers.
The “rattle” that you hear when you experience this common engine problem is the Wastegate actuator arm/rod improperly functioning from general engine wear and tear.
N54 Wastegate Rattles Symptoms
- Rattling noise coming from the engine
- Low boost engine codes
- Significant loss of power
- Smoke coming from exhaust (oil leaking from turbo seals)
Why Does the Wastegate Fail?
The N54 Wastegates fail from simple wear and tear of the engine. Over time the actuator and rods of the turbocharger wear down, resulting in rattle and boost control issues. In this case, running higher levels of boost (psi) on your turbochargers will likely increase your chances of Wastegate failure. Yes, this means running a JB4, Cobb, or PROcede tuner will increase the likelihood you blow your turbo’s. This is because the extra boost pressure created from these tunes puts more strain on the turbochargers, creating accelerated wear and tear.
How to Decrease the Chances of Wastegate Rattle
We aren’t saying don’t tune your N54 (obviously). Zach and I both rune JB4’s, as do thousands of other N54 owners. If you are running a JB4 on Map 5, you likely won’t run into this issue until you are nearing 100k miles or more. Zach blew his turbo’s twice (around the 80k mark), you can read about it here.
When you run the risk of blowing your turbo’s is when you start experimenting with serious psi/boost pressure. If you are trying to run 22psi, yes this is more likely to happen. Stick to appropriate boost levels and you will be fine. Additionally, make sure you always let your engine warm up to AT LEAST 160 degrees (Fahrenheit) before you get on the gas and seriously spool the turbo’s.
How to Fix N54 Wastegate Rattle: Repair Options
The turbochargers are warrantied for up to 10 years or 82,000 miles. When you take your N54 to the dealership, they will first try to update and adjust the ECU. They do this by readjusting the slack in the actuator arms, which will typically work for a little while, but your car will be a ticking time bomb at this point.
BMW’s hope is that the ECU update will last long enough for you to no longer be on warranty. Make sure you get them to replace the turbo’s when this happens!
Replacing the turbochargers is extremely expensive. New turbo’s will cost you upwards of $1,000, and it takes nearly 6-hours of labor time just to get the turbo’s uninstalled. Then you have the cost of install, etc. This is replacement is usually 15+ hours of labor.
A lot of people will elect to upgrade their turbo’s if they experience Wastegate rattle and are no longer on warranty. The cost of labor won’t change (for the most part), so the only difference in cost is the cost of the upgraded turbo’s. You can get your turbo’s rebuilt, but since you are already paying all the labor costs, why not get a little extra power out of it :D.
You can read our upgraded turbo’s blog post here (when its fully written). For the sake of length, I won’t go into it further on this post.
Replacement Cost: $6,000 from the dealer, $3,500 from a local shop
DIY Difficulty: Dealership mechanics hate to repair these
Good youtube video: https://www.youtube.com/watch?v=VQD6tITYH7k
3. N54 Leaky or Clogged Fuel Injectors
The N54 fuel injectors run hand in hand with the high-pressure fuel pump we discussed earlier in this guide, so I guess it is no wonder that these are a common N54 engine problem as well. The fuel injectors are responsible for spraying the spark plugs and ignition coils with gasoline, so that they ignite on start-up and every revolution thereafter.
Fortunately, there are some useful preventative measures that can be taken to reduce the likelihood of leaky fuel injectors. Read on to learn why these injectors leak, what the symptoms are, and how to avoid this problem all together.
Why do N54 Fuel Injectors get clogged?
As mentioned above, the injectors spray the spark plugs with gasoline. Carbon naturally builds up inside the engine, but this carbon is typically burned off when the engine is ran hard and heated up to high temperatures. When the engine cools down, the carbon can get stuck inside the engine and inside the injectors, causing clogging. Clogged injectors can also cause a bad fuel spray patter.
A bad spray pattern can result in the plugs either getting too soaked, or not soaked enough in gasoline, which can create misfires, and cold-start problems.
What are Leaky Fuel Injectors?
Due to the way the N54 fuel injectors are positioned, if they leak, drips of gas will land on the spark plugs. When the injectors leak a considerable amount, this will make the spark plugs very wet, which will in turn make it harder for the engine to ignite the spark plug and start the engine. This will result in difficulty starting the car, and possible misfires upon start and while driving.
N54 Fuel Injectors Failure Symptoms
- Hard time cold starting the engine
- Misfires (especially upon a cold start)
- Excess oil and gas on the spark plugs
- Rough engine idle
These symptoms could either be the result of a leaky fuel injector, or a clogged fuel injector. The fortunate scenario is it’s just a clogged fuel injector. If it is a clogged injector, you can follow the maintenance steps below to help solve the problem. When it is a leaky injector causing these symptoms, then you will likely need to replace the injectors (which is expensive).
Maintenance to Avoid Fuel Injectors getting clogged
Alright, there are 3 main things you can do that will be astronomically beneficial for your N54: these will help reduce the chance of your injectors getting clogged. While they will be beneficial overall, they may not reduce the chance of your injectors leaking.
- Use an add-on Mishimoto Oil Catch Can: aftermarket oil catch cans are the best addition to your engine when it comes to reducing carbon buildup. They are well worth the price if the long run
- Run E85 Ethanol Cleaner through your fuel system occasionally.
- The bottles cost $13, buy 5 bottles and do this once per month. The fuel cleaner will help release the carbon build-up in your engine and fuel injectors, and create smoother running conditions
- Get your N54 Walnut Blasted: read our post on N54 walnut blasting. Walnut blasting, for lack of better words, blasts all the carbon gunk built up in your engine away. This should be done on N54’s every 30k miles or so, especially if it is tuned.
- Put your engine to work: warm up the engine at low speeds, and then take the car onto the highway and run it for 20 minutes at 4500rpms. After doing this 3-4 times, you will likely clean out enough carbon buildup to reduce clogged injectors
N54 Fuel Injectors Repair Options
Another BMW warrantied part. The nice thing with these common BMW engine problems is that BMW actually acknowledges it is a problem, and gives you a better warranty for it. The N54 fuel injectors are warrantied for 10 year or 120,000 miles.
If you are under warranty, BMW will try to only replace the fuel injector that is leaking. MAKE THEM REPLACE ALL! If you have one injector leaking, it is likely more will follow soon after. Give the dealership a little push and shove and they will replace all of them.
If you don’t have warranty
As previously mentioned, try the above maintenance techniques to see if the problem is only a clogged fuel injector. If you get your engine walnut blasted and you are still experiencing this issue, then it is probably a leaky injector.
The injectors are expensive (about $120/ea), and I do strongly recommend replacing all 6 at the same time to save on labor for when others start to leak.
Replacement Costs: ~$1,400 for injectors, $100 for BMW to code them, plus install at a shop if you don’t DIY
DIY Difficulty: Intermediate
4. N54 Chargepipe Failure / Leaking Boost
Stock N54’s owners are lucky on this one…because you likely won’t run into this issue. N54 chargepipe failure and leaking boost (caused by chargepipe failure) are both primarily the result of tuned engines running above stock boost/psi.
If you read our “How-to Build a 500HP N54” guide, you will notice that we highly recommend upgrading your chargepipe when you tune your engine. Note, this is only necessary if you are running a flash tune, such as the JB4, Cobb AP, or PROcede. Other performance parts won’t (in most circumstances) burst your chargepipe.
The N54 Chargepipe holds boost pressure until release by the blow off valve
Turbocharged engines build up boost pressure (psi) inside the engine, which is causes the increased power and speed associated with them. The chargepipe is a component of the turbo system, and holds boost until it is released out of the system by the blow off valve.
BMW built their N54 chargepipes out of plastic, which is why this failure gets to make it on our most common list. It happens a lot!
Why does the Chargepipe leak or crack?
Under high boost applications, such as running a JB4 or other flash tuner that increases the turbo’s psi, the plastic chargepipe simply cannot handle the pressure. The high pressure can either cause the chargepipe to leak boost pressure (which will cause a loss of horsepower), or completely crack or pop.
Benefits of Upgrading your N54 Chargepipe
If your chargepipe is working properly and not leaking, then it doesn’t matter if it is made out of plastic or stainless steel. Meaning, there are no performance/horsepower benefits to upgrading your chargepipe. With that being said, an upgraded chargepipe is not necessary for stock N54’s, or N54’s running stock boost levels. The chargepipe still can fail under stock boost pressures, but it is a lot less likely.
If you are planning on running meth or ethanol, an upgraded chargepipe isn’t even a question.
For tuned N54’s, upgrading the chargepipe is a must! The question is if, it’s when. Do a search on the forums and you will read countless stories of drivers’ chargepipes bursting and popping off while driving.
Upgrading your chargepipe is a good preventative modification. If you are going to run high boost levels, it’s a must. That’s all that needs to be said. It is an easy DIY and a cheap part.
Upgraded Chargepipe Cost: $250
DIY Difficulty: Easy
5. Valve Cover Oil Leak
Another common area prone to problems is the N54 valve cover, and the valve cover gasket. The gaskets on these cars are very prone to withering away and degrading over time, which results in oil leaks, and a buildup of oil in your engine.
A second common issue is the valve cover cracking, which also results in oil leaks. Valve cover cracks are caused by heat cycling, or the transfer of heat from the block to the cover. The covers are plastic, and therefore are affected more by the increased heat created by turbocharged engines. A crack requires both the cover and gasket to be replaced.
N54 Valve Cover Oil Leak Symptoms
Common N54 valve cover oil leak symptoms are:
- Oil on the threads of the spark plugs, but not on the electrodes
- Ignition coils covered in oil
- Crevices of the head/valves are filled with oil
- Burning oil smell, possible smoke coming from valve cover
- Low engine oil light
This issue won’t throw any codes, which makes it hard to recognize sometimes. In severe leaking cases, you might get a low oil light on the dash once enough oil has leaked out. If your engine isn’t smoking or giving off a burning smell, the easiest way to diagnose this issue is to pop the valve cover off and inspect for oil. If there is a leak, you will usually see a buildup of oil underneath. Pop the coils out and inspect them to see if they are coated in oil. If you still are unsure, pull the plugs and look for oil on the spark plug threads, but not on the electrode (the tip).
Tuned and modified engines will not cause valve cover problems!
N54 Valve Cover Oil Leak Replacement
There are one of two scenarios here: you could have a simple leak from a worn down gasket, or you could have a cracked valve cover that it causing the leaking. If you just have a leak, you will only need to replace the gasket. If you head cover is cracked, you will need to replace the cover and the gasket. You can guess which is more expensive! Regardless, this is a problem that shouldn’t go unfixed for too long. And unfortunately, replacement is the only option. Always replace the gasket when you replace the cover.
Replacement Cost: $32 for the gasket. $308 for the cover (if you’re cover cracked) + labor. Do not go to the dealer for this, they will try to milk you for $1,000 just for labor! The DIY isn’t overly hard, but also isn’t a beginner’s task.
DIY Difficulty: Intermediate
6. N54 Carbon Build-up
If you read our fuel injectors section above, we touched on natural carbon buildup inside the N54 engines and how it can lead to problems with the injectors. Aside from clogging fuel injectors, carbon buildup in the N54 can result in sluggish performance, and misfires.
Carbon buildup is a result of Direct Injection fuel systems, which as the name suggests, injects gasoline at high pressures directly into the combustion chamber of the engine. Direct Injection systems allow for a lot more precise fuel measurements (think air to fuel ratios, etc.) than traditional injection systems.
Direct injection shoots gasoline into the cylinder, instead of the back of the valve. Therefore the valve and the ports do not get cleaned by the gasoline and other detergents as they normally would. This leads to a buildup of carbon deposits inside the valves and ports.
ALL direct injection engines suffer from carbon buildup, not just BMW’s, and not just N54’s. Audi’s and VW’s also have the same issues we are going to describe here.
N54 Carbon Build-up Symptoms
- Sluggish performance, noticeable loss of power
- Misfires, likely without any engine codes
- Hard starts
- Poor fuel economy
How to Reduce N54 Carbon Build-up
- Use an oil catch can
- Get your engine walnut blasted
- Use ethanol fuel injector cleaner
- Only use the highest possible octane (93+ preferably)
- Change your oil and oil filter every 7,500 miles at a minimum
- Switch off using different brands of gas
- Drive your car on the highway for 20-30mins at 4500rpms (once per month)
Your best bet, if you have never done anything to minimize carbon buildup, is to get a walnut blasting. This is the best place to start, and then use these tips above to prevent the carbon from building back up.
Walnut Blasting your N54 to Remove Carbon Build-up
Once your N54 hits roughly 45,000 miles, it likely has a good amount of carbon built up inside of the valves. The easiest, most effective, and most efficient way to remove this carbon buildup is through walnut blasting! This technique uses walnut shells, and blast theme at high pressure into your valves to completely wipe out all of the gunk.
While there might not be a huge improvement in “go-fast” performance, some people have seen HP improvement of up to 20HP, after walnut blasting their N54. In this case, you aren’t getting more horsepower per se, you are just unlocking power that had been lost from the carbon deposits. The most common benefits are increased throttle response, smoother idling, and overall smoother and improved performance.
Helpful forum post on walnut blasting: http://www.e90post.com/forums/showthread.php?t=682116
Helpful Products to Reduce N54 Carbon Build-up
7. Vanos Solenoid Failure
Read our guide all about VANOS: Diagnosing a Failing BMW Vanos System – When to Repair Your Vanos
8.Water Pump Failure
The water pumps on the N54 engine are another fragile piece of equipment. The water pump is responsible for pumping water into the radiator, in order to cool engine temperatures. Along with your engine fan, the water pump and radiator are important parts of your cooling system. The N54 water pumps typically fail around 70k-80k miles. Zach is upwards of 100k on his 335i, and still running on his stock pump, although we blew one on our 535i way before 70k too. But we can probably attribute that to Zach driving 125mph for a solid 15 minutes.
A lot of times these pumps will fail with almost NO warning signs! If you are lucky enough to get a warning sign or two, you will experience something like the below.
N54 Water Pump Failure Symptoms
- Engine overheating, above normal running temperatures
- Water pump and fan running noise is very loud
- Engine coolant draining abnormally fast
- CEL Code 2E84
N54 Failed Water Pump CEL Codes
- 2E84: replace water pump and thermostat (main code)
- FC 377A: Coolant pump switcher off due to blockage
- Check fuses F07, F09, 80, and 33
- Please comment to help me get more codes!
Water Pump Replacement Options
There are no quick fixes here, no easy fixes, and no cheap parts. Your only options is to replace the water pump and suck up the cost. The OEM part costs $400, and install will run you a few hundred more. This DIY will likely take you a good 8+ hours of work, if you are experienced enough to handle it.
Don’t replace your water pump with anything other than the OEM water pump. If you chose to, just know you have been warned.
DIY Difficulty: Experienced DIY’ers