BMW N54 Twin Turbo - Diagnosis and Repair - 0030FF Low Boost Pressure Error Code

I got a check engine light this August while on a family road trip. 205,000 km (145,000 miles) and I replaced both turbos 2 years / 15,000 km ago. The fact that it probably wasn't the turbos was comforting, but it still bothered me. I had a few other issues to sort out with the car - an oil pan leak and the replacement of both rear drive axles (leaking grease), so I figured I would get the car up on the Quickjacks and sort all this out at one. 

Low boost pressure can be caused by 3 main reasons:

1. Bad turbos (worn wastegate bushing, wastegate rattle issue). Turbo is unable to generate boost because the wastegate valve can't close completely, preventing the exhaust turbine from receiving energy, or more sinister failure such as worn or seized bearings; 

2. Vacuum control issues - turbo wastegate actuators not getting enough vacuum when demanded by the ECU - due to bad Pressure Controllers, bad Actuators, or vacuum leaks / blocked or collapsed vacuum lines.

3. Charge air duct leaks / burst charge air ducts, air duct connections have popped open, or Pop-off valves are disconnected from the charge air pipes. If boost is leaking, the pressure sensor won't detect boost. There's also a chance the charge air pressure sensor is faulty. 

A wise person once said, don't rule things out because you think they're fine, someone else said they're fine, or that you think they can't be the problem. They might actually be the problem, so make a diagnosis plan from most likely to least likely and be systematic.

Step 1 - Turbos

I had the advantage of having the exhaust system off the car (in order to remove the left rear drive axle), and the front right drive axle and bearing support removed (in order to repair the oil pan leak). So access to the downpipes, and rear turbo actuator was pretty good.

The first item to check were the wastegate bushings - I could access the rear linkage - everything was tight, nothing was loose. As expected for an almost new turbo. I expect that the front will be the same. 

Step 2 - Vacuum Control Issues

I disconnected the vacuum lines from the two wastegate actuators, where they combine and connect to the pressure controllers. I picked up a Mityvac handheld vacuum pump to help with the diagnosis. I then tried actuating the wastegate actuators - the front turbo actuator worked fine - I could develop 20 inhg of vacuum no problem, I could hear the linkage moving, and when vacuum is released, I could hear the linkage releasing. No problem with the front actuator. 

Testing the front turbo actuator in car, using the hose to the pressure controller. Holding vacuum.

The rear actuator was a different story. Apply vacuum to the line - and nothing. Vacuum would not build in the line, and the actuator would not actuate. I replaced these vacuum lines two years ago with the vacuum line supplied with the Turner Motorsports N54 turbo kit, the vacuum lines should be fine. So I decided to remove the actuator since it was accessible above the downpipe and test the actuator out of the car. 

Some gymnasitcs to remove the rear turbo actuator, but not impossible. 

When I tested the rear turbo actuator directly, it worked fine, no problem at all. It turns out the vacuum line I installed 2 years ago wasn't suited to the heat, and had essentially crumbled and collapsed. 

Rear turbo actuator out of the car

Note the breaks in the vacuum line. First issue found. 

So - I ordered 3 metres of 3.5mm silicone vacuum tubing, which should withstand the heat better. I wasn't finished with diagnosis on the vacuum system, I also tested the pressure controllers. 

Testing the pressure controllers was pretty simple, you can do this in the car. To test the pressure controllers, disconnect the two hoses and the electrical connection, apply vacuum to the inlet port (from the vacuum reservoirs) - and the pressure controller should be closed, and allow vacuum to build without releasing it. Both my controllers failed this test - they were leaking vacuum to the outlet port (to the wastegate actuators). I could tell because I could only build vacuum with the pump holding my finger over the outlet port. Second test would be to build vacuum, then slowly let it off by applying quick pulses of 12v to the controller electrical contacts (you can use battery power and test leads) - the pressure controller should allow you to slowly and evenly drop vacuum over several pulses. A bad pressure controller may let off all vacuum with a single pulse of 12v. Third - the pressure controller should be able to hold vacuum even during vibration (you can apply vacuum then tap the end of the controller with a small wrench or screwdriver). My controllers would lose their vacuum with minor tapping - when holding my finger over the outlet.

So - new pressure controllers ordered as well. That covers the vacuum control system diagnosis.

Step 3 - Charge Air Ducts / Air Leaks

This is fairly straightforward - just inspect the pressure side of all the air ducting around the engine. The only difficulty is that accessibility is poor, it's difficult to see everything. I was fortunate that I had the engine out of the car 2 years ago - I have a pretty good idea of where all the ducting runs and could feel around and use an inspection mirror to make sure everything is connected properly. Removing the underbody panels is necessary under the engine - so you can see the intercooler duct connections and make sure they're solid. In my case - I found a transmission oil cooler hose leaking onto the left intercooler connection, but all the intercooler hoses were fine. Check out my O-Ring repair for the transmission oil cooler quick connect fittings here. 

Left intercooler charge air connection. Solid, but covered in transmission fluid from a leaky quick connector. 

From above, you can inspect the charge air ducts arriving under the air filter. Both of my Pop-off valves were connected properly, but I decided to remove them temporarily to test them. If the valves are not actuating properly, they can cause a intake manifold pressure when you let off the accelerator. Using the handheld vacuum pump, connected to the Pop-off valve, you should see the valve open when vacuum is applied. In my case, only the front valve was working properly, the rear valve wouldn't open under vacuum. Another part to replace. 

Testing the Pop-off valve. You should see the valve open through the connection to the charge pipe.

Repairs

Replacing all the vacuum lines was pretty simple - just go piece by piece through the system and make sure you get the inlet / outlets on the pressure controllers in the right order. The RealOem vacuum line routing image helps here. 

Replacing the pressure controllers - also simple. I went with the Piersburg OE parts from Pelican for this. Good value. I tested the new pressure controllers with the handheld vacuum pump before installing them - they held vacuum perfectly out of the box - much better than the original ones. 

New Pressure Controllers installed

Replacing the Pop-off valve - also simple, 10 minute job. The connectors are a bit tricky working underneath the air filter housing, but patience gets the connection done. Don't forget to reconnect the vacuum lines. 

Road Test

With all the repairs completed, (and once the axles were back on the car, and the exhaust replaced), I got the car out on the road and tested it out. It certainly felt awesome - the car accelerated as good as when I first got it at 78,000 km, if not a little better. 

Boost pressure data from Carly

I logged boost pressure using the Carly app - and managed to hit one peak slightly over 2 bar on the first run - better than any peak this year. Car was sustaining about 1.7 or 1.8 bar in long, sustained acceleration (0 to 60 mph). 

So - successful repair - car is running amazing again. If you have any questions - feel free to use the comments below. 

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BMW E61 Turbo Replacement Project - Cleaning Intercooler, Radiator, Power Steering and Transmission Coolers

I made the decision to pull the engine and transmission out of the front of the car when doing the turbo replacement project. I was using quickjacks which give me about 24" of lift - and don't have a 2 or 4 post lift to be able to drop the engine and transmission out of the bottom of the car. One thing that really impressed me about this car was there are 7 heat exchangers / coolers around the front of the car: radiator, AC evaporator, power steering cooler, engine oil cooler, charge air intercooler, transmission fluid cooler and coolant / transmission fluid heat exchanger.

Charge air intercooler - lots of grit came out of the fins.

 It was pretty impressive the quantity of road grit that came out of virtually all the heat exhangers, particularly the intercooler, power steering cooler, and transmission fluid cooler. The AC evaporator, engine oil cooler and radiator protect themselves somewhat because they are stacked behind the transmission fluid cooler. The AC evaporator is quite exposed to grit and debris coming through the kidney grille at speed, blasting the paint and flattenning the fin material.

Halo of grit from flushing the intercooler. 

This car is winter driven daily - and exposed to road salt and grit all winter. The intercooler was about 30% blocked with grit, the power steering cooler about 50% blocked with grit, and the transmission cooler was the worst off - almost 100% blocked with grit.

Transmission cooler - almost completely blocked with road grit.

 Through trial and error - I found that the best method to clean all these aluminum parts was to initally flush with soap and water, and try to get as much grit removed using a high flow / low pressure water hose to avoid damaging the fin material. Once that was done, I used aluminum wheel cleaner - sprayed to soak into the fins as much as possible, and then flushed with water within the prescribed time (a few minutes of application only). This remove a good amount of grit. Then the third stage was to clean out grit using a dental pick set - I needed to do this with the worst heat exhangers only - and since these parts cost between $300 and $700 each - it was worth the time doing a few evenings of dental picking to rehabilitate these parts.

Front end during disassembly - note the sandblasting of the AC evaporator - leaving the kidney grille shape with two lines from a cross brace. 

The transmission cooler is the lowest cooler on the car - and the most packed with grit.

Transmission cooler - almost completely blocked with grit.

During the dental picking, I also straightened and lifted any folded fin material - it's time consuming, but for me it was worth it.

Radiator after cleaning with aluminum wheel cleaner. 

AC evaporator after cleaning with aluminum wheel cleaner. 

Intercooler during cleaning - all the metal and fins were in good condition without any pitting at the hose mating surfaces.

One final thing to note - I replaced all the o-rings / sealing rings at all the hose interfaces to help ensure I wouldn't have any leaks at startup. Now that the car is on the road, running, and AC system charged - I can state that it was worth the effort - no leaks at all from any of the systems - cooling, power steering, transmission cooling, engine oil cooling. All good.

Front end with all the coolers replaced. Shop dog hanging out the garage. Not easy keeping the dog clean....

I'll post some additional articles with lessons learned from this project, hopefully it can help others out when doing similar work.

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. If you're interested, you can help support this site by using the following links to Amazon.com in the United States. Turbo parts were supplied by Turner Motorsports. Other parts were supplied by Pelican, BMW Park Avenue in Brossard, and eEuroparts.

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BMW E61 Turbo Replacement - Engine Subframe Powdercoating, Steering Rack Rebuild

In order to pull the engine out of the front of the car with the transmission, the subframe needs to be dropped in order to allow the oil pan to pass over the steering rack. With the subframe on the floor, it was pretty easy to clean it up and check the condition of the subframe and steering rack.

Here's the subframe. Carbon steel construction, with one engine mount, 2 heat shields and steering rack attached.

The engine subframe on the BMW E61 is fabricated from carbon steel, painted or powdercoated black in the factory. My car is 9 years from the date of manufacture, and has been operated in Toronto and Montreal its entire life, subject to Canadian winters and road salt. What's interesting is that there is virtually no rust anywhere on the steel and aluminum body components. Most of the underbody structural and suspension components are made from aluminum - like the rear suspension frame, and the front suspension arms. There are a few components which sufferred from corrosion - the subframe, some of the aluminum heat shields, particularly at attachment points to the body, and one driveshaft tunnel brace also made of steel which I decided to replace.

The subframe was the one component of the car showing the most significant rust damage

Once I had a look of the extent of the paint bubbling and corrosion on the subframe, I decided that I didn't want to invest the time to try to clean it up and treat the corrosion myself - I had lots of other things requiring attention, like getting the new turbos, head gasket, oil pan gasket, etc on the engine and get the engine / transmission ready to replace in the car. So I decided to strip the subframe, remove the steering rack, and take the subframe to a local powdercoating shop to have it sandblasted and coated.

In preparation for sending out the steering rack - I measured the tie rod locations precisely for setup on reinstallation.

I found a local powdercoating shop that normally does industrial work, and the owner was a bit of a car guy and accepted to do my subframe for $150 - which was a great deal in terms of how much time it saved me from cleaning this up myself.

Subframe back from Powdercoat - beautiful.

He did a great job of sandblasting out all the rust, you can see in the powdercoat finish some of the pitting in the steel which was now overcoated, this should help keep the car on the road for another 10 years. He also protected all the studs and weldnuts from powdercoat - I didn't have any threading or tapping to do - which also saved time.

You can see some of the rust pitting in this photo - right hand motor mount area.

And some of the pitting here.

For the steering rack and axle half shafts / CV joints - I took them all to Axle Automotive (Capital Dominion Radiator) on Gladstone Avenue in Ottawa for rebuild. The rear axle half shafts were both spraying grease, and the fronts were fine but I had them repacked with new boots as a preventative measure anyway. They stripped down the steering gear, cleaned it, replaced the rod seals and boots, and the steering gear seals. I had the option of having the rack painted black - I opted to keep it natural aluminum. It turned out really nice - and now with the car on the road I can report that the steering feel is excellent - rack is performing like new. The price for the rebuild was very good - better than I could find at any shop in the Montreal area.

Front axle half shafts and steering rack - back from rebuild with all new boots. 

The aluminum body of the steering gear shows some oxidation - purely cosmetic and something I can live with. 

One thing to note is that all the bolts holding the subframe to the car front frame are torque to yield type fasteners that need to be replaced when loosened or removed. I did purchase new fasteners for the subframe.

Subframe prepped with heat shields, steering rack, left hand motor mount and power steering lines ready for the motor.

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. If you're interested, you can help support this site by using the following links to Amazon.com in the United States. Turbo parts were supplied by Turner Motorsports. Other parts were supplied by Pelican, BMW Park Avenue in Brossard, and eEuroparts. Capital Radiator in Ottawa did the steering rack rebuild.

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BMW E61 Turbo Replacement - New Head Gasket, Oil Pan Gasket and Oil Level Sensor Gasket

So this is the point where your spouse really begins to think that you're crazy, and wonders when you're going to get out and get a real job....

Since we're this far into it, by this time I had made the decision to switch out any suspicious seals, gaskets, o-rings, and try to do a proper job of this. I separated the head from the engine. You need to remove the timing chain from the VANOS camshaft gears. In order to remove the camshaft gears, you need to lock the camshaft into position using the camshaft lock tool - part of the camshaft timing tool set for the N54. Procedure is as follows - move the engine to top dead center cylinder one - and you can make sure you're in top dead center by looking for the laser engraved part number on the camshafts - just behing where you insert the camshaft locking tool. If you can't see the part number - you're 180 degrees away from top dead center and won't be able to remove all the head bolts. 

With camshaft in TDC position - grooves in the camshaft allow access to the head bolts underneath

Unbolting and torquing the heads - you're going to need a set of long hex sockets to access the fasteners. I kept the camshaft lock on the head the whole time the head was off during cleaning. 

Head split from engine. Note the camshaft lock tool (black).

With the head off - it's time to get everything cleaned up. I used brake cleaner and very mild abrasive scouring pads to gently remove the oil and carbon deposits. It worked well.

N54 engine block with head removed. No major difference in carbon buildup on the pistons. Note the zip tie holding the timing chain to the timing chain guide - this prevents the timing chain from falling off the bottom sprocket.

 The head gasket has factory applied silicone sealing rings applied. With the old head removed, I could see some places where oil had started weeping past the head gasket.

Front of the block - oil weeping past head gasket - timing chain cavity

 When I got down to cleaning the engine block - I cut fingers from vinyl gloves to block the coolant passages and help prevent debris from getting down into the coolant and oil passages. Very important - make sure you remove all this before you reassemble the engine for obvious reasons.

Vinyl glove pieces used to seal oil and coolant passages from debris during cleaning.

With the block mating surface clean - now is the time to check that the block is flat using a machinist straightedge.

Engine block cleaned, ready for head gasket and head.

 On to cleaning the head. This took quite a bit of effort to get the mating surface clean. When you factor in the time required to clean the oil from the intake passages (walnut blast) - in retrospect - I would have had the block taken into a machine shop for disassembly, cleaning, and a cleanup cut off the head surface. For the money I would have spent - it would have saved 40 hours of work in my garage... live and learn. I'll do a post on the intake valve cleaning and the problems I ran into there.

Head cleaned, ready for inspection and verification of flatness. 

 I had three places in the head where there was very minor erosion of the aluminum surface. Best option would have been to take the head into a machine shop to have a cleanup milling cut done. I cleaned the erosion the best I could, then applied a very thin coat of copper gasket maker to the eroded surfaces in the hope it will improve sealing of the head gasket. Time will tell how well this works.

Copper gasket sealant on a few eroded surfaces of the head. There was no erosion anywhere on the block.

 The assembly of the head to the engine was straightforward. Make sure you use new fasteners - they are all torque to yield fasteners and can only be used once. Torquing those fasteners is a bit tricky - you apply an initial torque with a torque wrench, then a defined turn in degrees. Make sure you follow the manual for your car for your torquing instructions.

Plastic valve cover, aluminum oil pan. Cleaning up for reassembly.

 Initially I thought I could get away without replacing the seals on the oil level sensor, so I left it in the pan and set about to cleaning the mating surfaces. Same procedure as for the heads - brake cleaner and scouring pads.

Mating surfaces cleaned on the oil pan - ready for reassembly with new gasket. 

 The aluminum oil pan gasket fasteners are aluminum torque to yield type. They take a very small initial preload - I used my 1/4" torque wrench from my bicycle repair kit to do the initial preload.

1/4" torque wrench on aluminum oil pan bolts. 

 To apply the 60 degree turn following the intiial preload, I did a wrap of vinyl tape around the torx socket - and made two marks 60 degrees apart. Makes measurement of the final angle torque application very easy.

 I followed up with a new magnetic drain plug.

Magnetic drain plug and sealing washers. 

Oil level sensor port - very dirty. Ended up having to purchase a new O-ring and clean this up properly.

Oil level sensor port cleaned up - fair bit of minor pitting, but the o-ring sealing surface wasn't too bad. 

I cleaned up the sensor instead of replacing it. Much gunk inside, came out nicely with electrical contact cleaner (safe for plastics). Looking at this - this is another good reason not to try to push oil change intervals on a turbocharged aluminum VANOS engine - you can see the effect that running high mileage oil has on internal components.

I used electrical contact cleaner to flush out the inside of the oil level sensor - worked well to get all the old oil out. 

A little copper silicone gasket sealer on the o-ring surface to help ensure a good seal of the level sensor despite the pitting.

I'll try to get a few more posts done - lots of lessons learned with this project that I want to share.

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. If you're interested, you can help support this site by using the following links to Amazon.com in the United States. Turbo parts were supplied by Turner Motorsports. Other parts were supplied by Pelican, BMW Park Avenue in Brossard, and eEuroparts.

 

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BMW E61 Turbo Replacement - Pulling the N54, and Stripping the Engine

Once all the electrical and plumbing was out of the way, and the exhaust, heat shields, driveshafts and drive axles removed, it was time to pull the engine. I initially planned to leave the transmission in the car, but a leaking rear transaxle seal made me decide to pull it out with the motor. We hooked up the engine hoist to a load balancing beam so that we could easily change the lift point with respect to the center of gravity. This ended up working very well, and was essential when pulling the transmission with the engine. 

Starting the lift - this is as far as you can go without lowering the steering gear and engine support crossmember

One we started lifting, we quickly realized that the X-Drive front differential would not clear the steering box of the steering gear with the lower crossmember in the car. As soon as we dropped the crossmember - the engine and transmission popped forward without much effort.

Engine and transmission out of the car - complete with front differential and transaxle. Heavy combination.

Next step was to separate the engine from the transmission. We were having difficulty with this - and thought that we had left a bolt in - which ended up being the case. We actually snapped one of the aluminum bolts clean in the engine - the head was hidden behind a gusset on the side of the transmission - we didn't see it with the transmission resting close to the floor. This ended up not being an issue - as all these bolts need to be replaced anyway, and the broken bolt backed easily out of the hole - no problem extracting.

Transmission on a dolly with castors, steering rack and crossmember on the ground.

Beer time.

First order of business before putting the engine on the engine stand was to remove the rear crankshaft oil seal. I thought this had been leaking, but it turns out it was still sealing well at 185,000 km. I bought the new seal and will replace the seal anyway. You can see oil coming down from the top right of the head through the gap between the engine and the bellhousing - this oil was coming from the area of the rear turbo.  

This seal pops out easily with the assistance of a couple of screws drilled into the seal. 

Claw hammer to remove the seal using the screws

Old oil seal - oil grooves are still in reasonable condition. Will replace anyway.

Since all the fasteners on the block are going into aluminum, and my torque wrenches are about 25 years old - I decided to check and calibrate the torque wrenches before I took down my engine crane. I just clamped a small vice to the arm of the crane, and held the socket of the torque wrench in the vise. I then loaded the torque wrench using a 5 gallon bucket of water and steel weight - adding water until the torque wrench would click. I would then measure the weight of the bucket, and apply the factor of length to come up with the actual torque. My 1/2 torque wrench recalibrated nicely with a small adjustment, and I'm within about 2% of torque. My small 3/8 torque wrench seems to have lost it's linearity across the internal spring - I could not get it to 5% across the measurement range and discarded the wrench. Quick order to Amazon to get the Tekton 3/8 clicker torque wrench to get me through the job. 

 This morning I got onto removing the turbos from the block. This went pretty quickly without much hassle. One thing that I've noted with this whole process however - is that it's really handy to have a few different sets of torx and e-torx bits - because sometimes you need a long bit, sometimes you need a small short bit, just to fit into the limited spaces where you're working.

Short 1/4" drive torx bits to get into tight spaces. 

Long torx to get at the manifold bolts. 

 It took about 2 hours to strip everything off the right hand side of the engine, including the bearing support for the front right drive axle, and the differential from the other side.

 Two of the exhaust manifold studs stuck in the block with the E-Torx head broken off - needed to jam 2 nuts together to get these last two out.

Jamming 2 nuts together to remove last two exhaust studs.

 Oil stain on the front differential was coming from the top vent. I'll be replacing the vent along with the seals - already have the vent on order.

 Removing the pan was fairly quick - had to remove the power steering pump first.

Turbos, oil and cooling lines, differential and oil pan removed. 

 New problem encountered - looks like my head gasket is leaking oil from the front right corner of the motor. The area below the head gasket is wet, and I don't think it's come from anywhere else. With everything off the engine, especially the turbos, now is the time to do this.

More to follow. I'll start with replacing the front and rear main oil seals, the oil pan gasket, and do the intake valve walnut blast. I'm researching what's involved in doing the head gasket now.....

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions. If you're interested, you can help support this site by using the following links to Amazon.com in the United States. Turbo parts were supplied by Turner Motorsports. Other parts were supplied by Pelican, BMW Park Avenue in Brossard, and eEuroparts.

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