# Carbon Build Up (CBU) on E70 35d w/ 72k + Fault Code 46B7



## rippjd (Apr 30, 2006)

I searched for a CBU (Carbon Build Up) thread to add the photos of my recent intake manifold remove, clean and install, but didn't find a good one specific to the E70 X5 35d. If you have one I can ask this to be moved...

Premise:
2010 X5 35d at 72k miles
Unfavorable driving profile for the last 1.5 years (mostly short trips < 10 miles)
Fault Code 46B7 DDE: Swirl-flap actuator
General concern about CBU

Action:
Install clip onto pivot shaft of swirl flap motor per SIB 131510 "M57Y DDE Fault Code 46B7 Swirl Flap Actuator"
Clean intake manifold per ISTA/D (Rheingold) repair instructions 11 12 800 (see attached PDF)
Inspect cylinder head intake ports and valves to determine CBU status

Observations:
Interior of plastic intake manifold had a fairly even level of moist (oily) carbon build up. 
Absolute manifold pressure sensor was not plugged, but did have some CBU on the end of the sensor which could be easily wiped away. 
Metal swirl flap "doors" had 1 - 3 mm of CBU on the back side, front side was much cleaner, but still no shiny metal visible
Some swirl port gaskets on bottom of intake manifold were rigid and difficult to remove
Swirl flap rod is held in place by 2 plastic tabs which are part of the intake manifold (i.e. if you brake them you need a new intake manifold!)
Soaking the manifold openings in Purple Power cleaner / degreaser, plus a little scrubbing with a nylon brush was sufficient to clean those areas
CBU on engine intake opening only went about 1.5" deep, see photo, also moist (oily)
There was no CBU on tangential swirl ports
My boroscope has a limited bend radius, but the intake valves all looked clean, so no need to walnut blast as far as I could tell!
IPCAPITAL did some good work experimenting with different solutions for filtering the oil droplets out of the crankcase ventilation system. I may pursue one of these:
http://www.bimmerfest.com/forums/showthread.php?t=774371
http://www.bimmerfest.com/forums/showthread.php?t=780433

Tips
- ODJOB brand 7 gallon bin (Lowes) was just about the right size for cleaning
- 2 gallons of Purple Power cleaner (Autozone) was insufficient to submerge the intake manifold up to the tops of the swirl flags, had to tilt the bin at an angle, so I would buy 3 gallons next time
- I looked at other cleaning solutions, but most did not recommend use with plastic, or did not say they were plastic "safe"
- The "BMW Universal cleaner" is 83-19-0-413-478 for a 20 Liter container, but may not be available in the USA
- Instructions say to ad "Slip lube" to the gasket on the inside of the charge air hose, I use silicon o-ring grease
- 6 bolts + 7 nuts on intake manifold are all torqued to 8 Nm
- Disconnecting the sensor on the back of the engine is difficult as the release tab faces the engine, but makes access to the last intake manifold nut easier, recommend a mirror to see its orientation
- ISTA/D says the 4 HEX bolts for the EGR valve to Intake Manifold are torqued to 8 Nm, but the 3 HEX bolts for the Throttle Valve to EGR are 19 Nm. SIB 110613 on the support bracket says 8 Nm for the 3 HEX bolts, so I'm assuming ISTA/D has an error and all 7 HEX bolts are torqued to 8 Nm.
- Transverse reinforcement bolts torqued at 10 Nm, then turn 90 degrees
- Tension struts are 19 Nm, then turn 90 degrees
- Camshaft Pulse sensor (opening to inspect TDC) is 2.3 Nm

Repair Instruction comments
- indicate to remove the front cooling fan, but I'm not sure why other than you would gain more clearance to move the charge air hose out of the way?
- indicate to disconnect the harness from the pressure sensor on the charge air hose, but I see no value
- indicate to remove the left strut brace, but I see no value unless this is how you slide the rear acoustic cover off? the tabs coming off the aluminum strut mount just above the engine make it almost impossible to remove without tearing the acoustic foam. I cut my right tab off with a hack saw (cut-off wheels would produce too much aluminum dust for my liking) and now have clearance
- indicate NOT to remove the swirl flap actuator, but an older version told you to remove it in order to have the intake manifold sent out for cleaning. I removed mine and have not seen any consequence

I probably removed < 5% of the CBU from the intake manifold, but my goal was to make sure the openings were clear and the swirl flap "doors" didn't bind... if I wanted most of the CBU gone I would find a radiator shop for ultra-sonic cleaning after I removed the swirl port assemblies along with all the metal or rubber hardware.


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## finnbmw (Jul 6, 2008)

Great write-up, thank you! My 2010 X5d with the same miles (71,000) is throwing the 46B7 and 46A7 codes intermittently. Check light comes on, stays for a while and then goes out. It happens under no specific condition. I could be at idle or cruising along the highway. I am assuming one (or more) of the swirl flaps sticking due to CBU build up. My miles are mostly highway.

How does your X5 drive now? Any difference?


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## rippjd (Apr 30, 2006)

finnbmw said:


> How does your X5 drive now? Any difference?


I thought the idle was a little quieter, but that could just be in my head. I'm not the primary driver.

In case you have ISTA/D, there is a job to run the range of motion for the swirl flap motor. Mine came back at 95% if I recall correctly. I haven't re-run it since the cleaning and clip installation.


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