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 Tailgate Hydraulic Lift Cylinder Replacement - 5 Series Touring

About 2 years ago, I refilled my tailgate lift pump hydraulic reservoir, it had gotten low, and the tailgate no longer opened fully. I wrote a post at the time about replacing the ball joints and refilling the hydraulic pump. This re-occurred recently, except this time the fluid was escaping from the hydraulic cylinder, and not the pump. The seals on the lift cylinder are not replaceable, the cylinder is not rebuildable. The end caps are crimped to the cylinder. 

BMW E61 Tailgate Lift Cylinder - Note the weeping seal, and the crimps in the cylinder wall.

So - what to do? I managed to find a decent looking cylinder complete with hydraulic lines and pump on eBay, from a European vehicle. Canadian winters and cold weather are hard on components like these, hopefully the part I purchased has had an easier life and will serve me for the rest of the life of the car...

Note the oil crud buildup in the well under the cylinder - the cylinder was losing lots of fluid.

So - with the replacement part in hand, it was time to get at the repair. First step is to get access to all the hydraulic lines. You'll need to do the following preparation:

• Remove the left rear D pillar trim which encloses the cargo cover mechanism
• Lower the headliner 
• Remove the left side cargo trim - both the access door and the wheelwell cover

Starting with the D pillar trim, it is fairly straightforward. Start by removing the tailgate weatherstrip. With that removed, there are two screws which hold the cargo cover mechanism to the inside of the D pillar trim - at top and bottom. At the bottom, the screw is exposed and easy to find. At the top, there is a rubber bumper which limits the top of travel for the cargo cover, under this bumper is the second screw. 

Removing the D Pillar trim, note the body clips (top and bottom) and cargo cover mechanism

Top screw retaining the cargo cover mechanism (inside of D pillar trim)

Note the rubber bumper - remove this to access the top screw

Bottom fastener exposed next to cargo cover mechanism

With the D pillar removed, you can now drop the headliner. To do this, you'll need to remove the two rear roof speakers, and also remove the clip for the cargo screen / roof attachment. You shouldn't have to remove the C pillar trim, nor the D pillar on the other side. 

There is a screw inside the cover which allows you to remove this clip

Removing the left side cargo wheel well cover is a bit tricky - you need to remove the left side passenger seat bolster, lower the seat, and then remove the plastic cover underneath the quarter window, just behind the C pillar. There doesn't seem to be an elegant way to do this - I just ended up forcing it with a trim tool and it eventually popped out with one of the plastic tabs broken. With this part removed, you have access to all the fasteners along the top of the wheel well cover. Everything else is fairly straightforward. 

Removing trim cover behind C pillar

With the side panel removed, you'll need to access the hydraulic pump and it's connections. You may need to remove a radio module to gain access - be very gentle with the purple fibre optic connections - if you break one of these, you may be looking at a trip to the dealer and a lot more hassle. 

Remove the hydraulic lines to the pump. Just remove the two wire clips, and the hydraulic lines will pull straight up. Take care when removing and inserting these connections, to my knowledge, the seals inside the connectors are not replaceable. 

Connections to the hydraulic pump are foolproof - Red to Red, Blue to Blue. 

This is a good opportunity to inspect the pump and see if it is leaking fluid from the accumulator. You may notice a puddle of fluid underneath the pump, if it's bad, it will run down underneath the cargo floor towards the spare tire well. This is a good time to remove the pump and replace the accumulator piston seal - check out my post on resealing your hydraulic pump here. 

With the hydraulic lines disconnected from the pump, you'll need to disconnect the limit switch electrical connector which is directly above the left rear speaker. This will avoid damage to the harness when you're removing the cylinder and lines. 

Lift cylinder limit switch electricla connector above left rear speaker

The hydraulic lines curve around 180 degrees clipped to the roof, just left of the left rear corner of the sunroof. With the headliner dropped, you'll need to access the clips and detach the hydraulic lines. Take a few photos and note the routing of the hydraulic lines with respect to the electrical harnesses and sunroof drain.

Disconnect hydraulic lines from two clamps holding lines to steel roof

This is an excellent time to verify your sunroof drains are not blocked, just pull the drain off the sunroof frame, and blow through some air to ensure it's clear. 

Sunroof drain hose, and connection at back of sunroof frame

With the two hydraulic lines disconnected, the electrical limit switch connector disconnected, and the clips removed holding the hydraulic lines to the roof, you can now pull everything through and remove from the car, from the exterior. 

Removing the cylinder and hydraulic lines. 

Installation of the replacement cylinder and hydraulic lines is essentially the same process in reverse. 

To assist with pulling the hydraulic lines through the roof to the opening left of the sunroof, I used a piece of stiff cable as a pull cable (old piece of TV coax cable). And - to assist with pulling through the electrical cable to the left rear speaker opening, I used a piece of twine. 

Prep for reinstallation - cable for pulling hydraulic lines, twine to pull electrical cable

Hydraulic lines pulled into the car, just need to pull through the electrical cable

To finalize the installation:

• Reroute the hydraulic lines, and clip them to the roof. 
• Do not forget to reconnect the sunroof drain
• Reconnect the limit switch connector under the left rear speaker
• Reinstall the cylinder to the ball joints - ensure they are properly lubricated for long life.
• If you've removed your pump and replaced the seals - reinstall the pump. 
• Reconnect the hydraulic lines to the pump - red to red, blue to blue.

There will be a lot of air in the hydraulic lines now - the best thing to do is to bleed the system following the procedures mentioned in my post on rebuilding the hydraulic pump here. 

If you haven't already done so, you may wish to replace the right side pressurized gas strut, this will help with lifting the tailgate and reduce the work done by the hydraulic system. 

Prior to reinstalling all the trim, this would be a good time to test and sure everything is functioning normally. 

Then replace the trim and the headliner.

Let me know if you have any questions or comments below. 

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BMW E61 Hydraulic Liftgate Pump Rebuild

The liftgate hydraulic pump in my 2010 BMW 535xi Touring lost hydraulic fluid level about 2 years following a quick fluid level top off. This time, there were two issues: i) bad seals on the liftgate cylinder; and ii) failure of the seal in the hydraulic pump accumulator piston, leading to leakage below the pump. 

I'll do a writeup on replacement of the lift cylinder separately. This post describes the replacement of seals and o-rings in the pump assembly.

BMW Hydraulic Liftgate Accumulator bore, piston and spring following dissasembly

When your liftgate starts struggling to reach the full open position, troubleshooting is fairly straightforward. The pump is located in the rear compartment, directly below the liftgate cylinder on the left hand side of the car, attached the left rear fender. To access, remove the left hand rear storage compartment door, then remove any audio components hindering access. Be very careful disconnecting the fibre optic connections on the audio components.

BMW Hydraulic Pump - low fluid level, fluid weeping from the accumulator (left side of pump)

Once you can see the pump, you'll note the "+" sign on the side of the plastic fluid reservoir. The oil level should be in the center of the "+" sign. In my case, the fluid reservoir was nearly empty, with traces of hydraulic fluid dripping from the accumulator housing (to the left of the fluid reservoir). 

Unfix the pump, lift to show bottom of accumulator and fluid weeping from vent hole

There are some gymnastics required to unfix the pump. Some can remove the pump without removing the left rear cargo area trim panel. If you're removing the pump for a rebuild, it may be easier to take the time to remove the trim panel. 

Once you have the pump removed from the car, and the hydraulic lines to the cylinder disconnected, you're ready to work on the replacement of seals. In the photo below, working clockwise from 12 o-clock, you have the motor top right. You have the mechanical pump mid right - between the motor and reservoir. The reservoir is bottom right. To the left of the reservoir is a hydraulic accumulator (a piston and spring designed to maintain hydraulic pressure, which holds the liftgate in the open position without the motor / pump running.) Just above the accumulator is a valve body, where the hydraulic lines connect and where the pressure sensor (top left) connects. 

Right side: Motor, pump and reservoir. Left side: Accumulator, valve body, and pressure sensor.

Removing the pressure sensor is straightforward. Remove the two hex head cap screws, and pull the pressure sensor straight up. The pressure sensor is sealed with a single o-ring - 9mm x 2mm. (All o-rings mentioned in this post are described by inside diameter (ID) then thickness. For outside diameter (OD) - double thickness and add to the ID.)

Pressure sensor with cap screws, and o-ring seal at base

I removed the motor, it is sealed to the pump with a single o-ring (41.6 x 2.4mm). I made no attempts to remove any pump components, I removed the pump, tried not to change the indexing of the drive spring, replaced the o-ring and replaced the motor. 

Motor removed. The o-ring stayed in the pump recess, it removed with a pick. 

In order to remove the accumulator piston, you need to split the two halves of the pump assembly. There are two long hex head countersunk screws which hold the two halves together. When you split the two halves, you'll note 5 oil passages which are sealed with small o-rings (4 x 1.5mm). Replacing these o-rings is very simple, just pop out of their recesses and clean any debris with a clean, lint free rag. 

Left and right halves separated - note 5 sealing o-rings.

Once you have the two halves separated, you can disassemble the accumulator. There are four hex head countersunk screws which hold the bottom plate to the accumulator body. Remove them slowly, and remove them equally (a few turns on each screw in rotation) because the bottom plate of the accumulator is under spring pressure. By separating the two halves of the pump, you ensure that the piston is at the top of the bore by removing any hydrostatic pressure remaining under spring tension. 

Accumulator piston removed from bore, note bits of piston seal disintegrating, dirty fluid

The piston will only come out of the bore with the two halves separated. Try to remove the piston square to the bore - to avoid the metal edges of the piston from scoring the aluminum bore. Same when replacing the piston, avoid rocking the piston in the bore, and insert squarely. The piston is a urethane U-cup seal, 35mm ID, 45mm OD, 7mm tall. 

Accumulator disassembled - piston, seal, spring, base and screws

Old accumulator piston seal on the left, new urethane U-cup seal on the right

New seal on the piston, old seal on the right

The final seals which are replaceable are the reservoir to pump seal which is a 39.4 x 3.1mm o-ring, and the reservoir drain/fill port, which is a 6.1 x 1.6mm o-ring. Reassemble in the reverse order of disassembly. Ensure that the accumulator is reassembled before assembling the two pump halves. 

After having rebuilt the pump, and disconnected / reconnected the cylinder hoses, you will need to bleed air out of the system. Reinstall the pump in it's normal location behind the left rear wheel well, but keep the reservoir off the pump. I used some 1/4" vinyl tubing to draw oil from my replacement oil can, and to reject oil and froth from the return line to an empty aluminum can. 

Bleeding the pump using vinyl hose. Note froth returning to the aluminum can. 

I used AeroShell 41 Hydraulic Fluid for this repair

Once the froth turns to a consistent air free oil flow, you can stop bleeding, remove the vinyl hoses, and partially replace the reservoir cup. I then refilled the reservoir using a syringe and vinyl hose to get the fluid level back to the "+" sign on the side of the reservoir. I used a regular stainless steel band clamp to hold the reservoir on the pump. 

Refilling the reservoir with the pump mounted in the car

Reservoir replaced, topped up to the correct level. 

I purchased extra seals when I completed this project, I'll put some seal kits up for sale on eBay for anyone interested in doing this repair.

I've made some repair kits available at this link. 

I've made some hydraulic fluid and refill kits available at this link.

Let me know if you have any questions in the comment section below. 

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BMW N54 E60 E61 x-Drive Oil Pan Leak Repair

If you have an X-Drive AWD BMW, the front differential is mounted to the side of the oil pan, and the right front drive axle runs through a sealed pipe through the oil pan. There are two aluminum covers which retain oil in the oil pan. I originally made a repair to one of these covers 2 years ago when I removed the engine to replace the turbos and do the oil pan and head gaskets. This repair failed almost immediately, and this post will explain why my original repair failed, and what I've done to make sure it doesn't happen again.

Right side of the N54 oil pan, with the right side drive axle and bearing support removed. 

Following my initial repair, the plate started leaking immediately. The engine had been reinstalled in the car, and the bearing support and drive axle already replaced, and the suspension bolted up and torqued. I didn't have the time or appetite to tackle the leak then, so I waited almost 2 years until I had a few other projects to work on to tackle this again. To start with, I removed the right side drive axle (half shaft) and the bearing support. Then, I removed the cover and discovered how little sealant remained between the sealing surfaces. The sealant remaining was brittle and was removed quite easily. I followed the sealant manufacturer's directions (wait 1 hour before applying full torque) but this delay is much too short to avoid squeezing out most of the sealant. This was my critical error.

Previous repair squeezed almost all sealant out of the gap between the sealing surfaces

 Clean up the mating surfaces. I use a plastic bristle brush, a plastic scraper, and scotchbrite pads soaked in brake cleaner to get the surfaces perfectly clean.

Plate cleaned up, old sealant removed, ready for re-sealing

I removed the bearing support and right drive axle without draining the differential fluid. I lost a very small amount of fluid through the axle tunnel, maybe 50ml or so (2 oz). I should top up the diff fluid when I complete the repair. Mating surfaces are clean.

Oil pan mating surface cleaned up, ready for resealing

 The last repair, I used a tube of sealant which I had on hand and was already opened. This time, I planned ahead, and made sure I had a fresh tube of new sealant for this repair.

Permatex Ultra Grey Gasket Maker

 Following manufacturers directions, I applied a 1/4" bead to one surface (the cover), and then assembled the cover with the fasteners, but not applying any torque. Just closing the gap to approximately 1mm, as evenly as possible on all sides.

Apply sealant to one sealing surface (not both)

1/4" 5mm bead of silicone, Circling the fastener holes (recommended in sealant instructions)

I waited 48 hours before applying torque to these cover fasteners - 2 N-m only. This seemed to compress the silicone nicely. I'll fill the oil pan with oil and check for leaks before replacing the drive shaft and bearing carrier - just in case I still have a problem.

Maintain a 1mm gap between sealing surfaces, wait 48 hours before torquing fasteners

The engine oil was refilled, and after another 48 hours, absolutely no sign of oil leaking from the plate. Looks like it will hold. 

Mate surfaces, but do not torque the fasteners. Tighten just until some sealant comes out of the gap

I've also found that I have a minor leak just above this repair - at the bed plate to block interface. A few drops of oil are seeping out around two of the bolt heads. To make this repair - the engine has to be removed from the car, and the bedplate removed (which provides access to the crank and crank bearings). This engine is at 205,000km now (approximately 130,000 miles) and this is a repair that I'd like to put off indefinitely. At least the oil pan to block gasket has held up nicely, no leaks so far. Same for the head gasket and valve cover gasket. 

If you have any questions, don't hesitate to ask in the comments below. 

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Rebuilding BMW Transmission Oil Cooler Hose Quick Connect Fittings

I pulled the BMW E61 into the garage last week to sort out a few issues - rear axle CV boots leaking, oil leak, and low boost pressure. On inspection, I found a leaking transmission oil cooler quick connect fitting, which was spraying oil on the charge air duct from the intercooler to the intake manifold.

The upper (pressure side) tranmission oil cooler quick connect fitting is leaking

I did some research on the internet, could not find any articles about people rebuilding these fittings. This hose costs $170 - expensive to replace for a simple leak. I figured since it was leaking anyway, I would try to take it apart and see if there were replaceable seals. The part numbers of the hoses affected are: 17227570973, 17227571978 and 17227571985.

Once the connection is separated, I took a pick and very easily removed two regular o-rings from the female side of the fitting.

It was easy to remove two standard o-rings from the fitting using a pick. I was careful not to scratch the inside of the connector shell. Once I had the o-rings removed, I noted there were two spacers made from plastic - one green spacer deep in the fitting, and one gray spacer just above the green spacer.

O-rings removed from the fitting, see the green spacer and gray spacer just above. 

The old o-rings were squared off, and not very pliable. They held their out of round shape upon removal. I measured the old o-rings and then estimated what the original uncompressed size would be. They appeared to be standard metric o-rings, and a quick trip to the local o-ring supplier yielded some potential replacements. 

Old o-rings above, new o-rings below. Two per fitting. 

Next step was to stuff the new o-rings into the fitting.  To start with, I used a pick to push the green spacer to the bottom of the fitting, and lift the gray spacer to the top of the fitting. This leaves a groove the width of two o-rings to fit the first replacement o-ring. I stuffed the o-ring into the fitting using some needlenose pliers. 

Start by pushing the green spacer to the bottom of the fitting.

Then - insert the replacement o-ring using needlenose pliers. 

I used the needenose pliers to insert the o-ring into the fitting just above the green spacer, and then to hold one side of the o-ring in the correct position while I used a screwdriver to massage the o-ring into position. With the first o-ring in place between the green and gray spacers, use your pick to push down the gray spacer (and the first o-ring) against the green spacer. 

First o-ring inserted above the green spacer. 

Next step, insert the second o-ring just above the gray ring just as before. With both o-rings inserted, I closed the fittings, cleaned them carefully to remove all traces of oil, so that any new leaks would be apparent. Following a run-up - the two fittings I repaired were both well sealed. I created this simple schematic showing how the o-rings stack in the fitting. 

I've purchased spare O-Rings - if you would like to purchase O-Rings to repair your own fittings, click this link.

If you're careful with the plastic ring and don't break it when disassembling the connection, you may be able to repair it. One other tip - if possible, before disassembling, wash the hoses with soap and water, and get into the release clip side of the fitting with a toothbrush to get as much grit and sand out of the fitting. Blow water out of the release clips using compressed air, and this will make the disconnection a bit easier. Comment below if you have any questions. 

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