Cleaning intake ports, piston crowns and combustion chamber with walnut granules (N74) (M760i xDrive 2017-2022)
Special tools required:
- 2 445 269
- 2 411 771
- 2 208 033
- 2 208 034
- 0 494 179
- 2 420 689
- 2 445 268
- 2 411 770
- 2 413 682
Follow the instructions below exactly. Nonobservance can lead to serious damage to the engine as well as personal injury!
Preparatory measures:
The engine and the engine compartment should be as free of dirt, sand and dust as possible. If necessary, clean and dry the engine or engine compartment beforehand with a hot water high pressure cleaner. The engine should be cooled down (< 40°C). If need be, allow the engine to cool down.
Note on the beam probes for cleaning the combustion chamber:
Do not oil or grease the threads of the beam probes or the moving parts. Granules and granulate residue can adhere to oily or greasy surfaces and make handling difficult or hinder. If necessary (e.g. in case of stiff movement) clean the beam probes with brake cleaner and compressed air; if necessary, clean the thread with a wire brush.
Preliminary work needed:
- Close the vehicle windows and doors. During cleaning, a lot of dust can be released.
- Disconnect the battery.
- Remove INTAKE PLENUM .
- Remove BOTH INTAKE MANIFOLDS
.
Attention! Protect or seal the dismantled collector and all other exposed openings and connections against access by foreign bodies or contamination!
- Carefully pack both charge air coolers.
- Remove IGNITION COILS .
- Remove SPARK PLUGS
.
Then replace the ignition coils to protect against foreign bodies. Do not plug in ignition coils.
Attention! If oil has entered the spark plug shaft, it must be completely removed. Granules and granulate residue adhere to an oily surface and impede/hinder further work processes and increase the risk of damage to the engine.
- Remove FAN COWL .
Protective equipment is required for the work listed below.
Prepare blasting device (81 29 2 208 034) with walnut shell granulate.
Clean intake valves/port:
Attention!
Crank engine at central bolt in direction of engine rotation.
When cranking backwards, the timing chain can skip.
Firing order: 1-7-5-11-3-9-6-12-2-8-4-10.
Turn the crankshaft in the direction of rotation on the central bolt (1) and place the piston of the 1st cylinder just before the intake BDC.
Observe intake valves on cylinder 1; turn slowly and stop rotation as soon as the valves close.
Attention!
Do not crank the crankshaft in reverse direction.
When cranking backwards, the timing chain can skip.
Check whether the intake valves are closed (see arrow).
Special tool 2 411 771 and 2 208 033 mounted as shown.
Cleaning of the intake port/intake valves:
- Connect vacuum cleaner to the jet vacuum adapter 2 411 771 .
- Position the suction adapter 2 411 771
(see image
) on the intake port of cylinder 1 (support person).
- Open the main valve on the blasting tool and switch the vacuum cleaner on.
- Insert beam probe 2 208 033 into the adapter 2 411 771
(see image
).
- Slide locking lever (1) to the front in arrow direction.
- Operate compressed-air valve (2) at stage one; compressed air can now flow in.
- Fully operate valve (3) at stage two; walnut shell granulate is now injected.
- Clean both intake valves and the intake port with swiveling and vertical movements of the beam probe.
- Cleaning time: about 15 - 20 seconds.
- After cleaning, continue at step one for at least 10 seconds with swiveling and vertical movements of the beam probe to stir up and suck off remaining granules.
- Close the shutoff tap on the special tool 2 208 034 and switch off the vacuum cleaner .
- Remove the suction adapter and evaluate the result (recommendation: endoscope or similar). If necessary, repeat procedure.
Cleaning the combustion chamber:
Turn the crankshaft in the direction of rotation on the central bolt (1) and place the piston of the 1st cylinder just before the intake BDC.
Observe intake valves on cylinder 1; turn slowly and stop rotation as soon as the valves opens by 3-4 mm.
Attention!
Do not crank the crankshaft in reverse direction.
When cranking backwards, the timing chain can skip.
Check whether the intake valves are opened by 3 to 4 mm.
Close the extraction adapter 2 411 771 using special tool 0 494 179 .
Connect a commercially available vacuum cleaner.
Screw the special tool for the combustion chamber roof 2 420 689 A into the spark plug bore flush as far as it will go and hand-tighten it.
Attention!
The beam exit of probe 2 420 689 A is directed upwards. Make sure that the tool is completely screwed in for the defined end stop and to protect the thread of the spark plug bore from contamination.
Prepare the beam device 2 208 034 using special tool 2 445 268 .
Ensure the correct position for cleaning the combustion chamber (probe A) or pistons (see arrow).
Connect vacuum cleaner to suction adapter 2 411 770 . Position the extraction adapter 2 411 770 at the intake port at the associated cylinder. The support person secures the suction adapter.
Turn on the vacuum cleaner.
Open the shutoff tap on the special tool 2 208 034 , see arrow.
Cleaning combustion chamber roof:
Screw in special tool 2 413 682 A for cleaning the combustion chamber.
Fasten special tool 2 420 689 A on special tool 2 445 268 .
Cleaning the combustion chamber roof - procedure:
Put the actuation to step two "clean" and immediately move the beam probe axially quickly from stop to stop. About three seconds for one in/out movement.
- Long arrow = fast movement
- Short arrow = short movement
Attention! Risk of damage at the piston crown. Prevent excessive contact with the piston.
After each in/out movement, turn the beam probe by about 10° to 15° so that the cleaning jet has reached every area of the combustion chamber roof after one revolution of the beam probe.
Total cleaning time: about 70 - 100 seconds.
The tommy bar on the connection of the beam probe points in the direction in which the beam exits.
See illustrations 1 and 4.
Unscrew probe 2 420 689 A and check the cleaning result with the endoscope.
If there are still deposits on the combustion chamber roof, repeat the procedure in these areas until the combustion chamber roof is clean.
Image 1
Image 2
Image 3
Image 4
Ensure the correct position for cleaning the combustion chamber (probe B) or pistons (see arrow).
Cleaning piston crown:
Screw in special tool 2 413 682 B for cleaning the piston crown.
Fasten special tool 2 445 268 B on special tool 2 413 682.
Cleaning piston crown - procedure:
Attention! Risk of damage at the piston crown. Prevent excessive contact with the piston.
Turn the beam probe in the direction of the exhaust. Put the actuation to step one "compressed air" for about five seconds in order to stir up the granules from the previous procedure and suck it out of the combustion chamber.
Put the actuation on step two "clean" and immediately pull the beam probe axially away from the piston crown by about 50 mm and push it back to the piston crown. About three seconds for one in/out movement.
- Long arrow = fast movement
- Short arrow = short movement
After each in/out movement, turn the beam probe by about 10° to 15° so that the cleaning jet has reached every area of the piston crown after one revolution of the beam probe.
See illustrations 5 to 7.
Check the cleaning result and, if necessary, improve it.
Total cleaning time: about 70 - 100 seconds.
Unscrew probe 2 420 689 B and check the cleaning result with the endoscope. If there are still deposits on the piston crown, repeat the procedure in these areas until the piston crown roof is clean.
The impurities that are in the middle of the piston crown cannot be geometrically blasted and can be ignored.
Image 5
Image 6
Image 7
After completion of the cleaning procedures, vacuum off all granules.
Thoroughly remove all granulate residue from the following areas:
- Combustion chamber
- Intake port
- Valves
- Spark plug shaft
- Threaded hole and sealing surface of the spark plug at the cylinder head
To do this, place the vacuum cleaner hose on the spark plug shaft and blow it with compressed air into the intake port/onto the valves and vice versa.
Attention!
Remove granules completely! If granules remains on the piston crown or in the intake port and the crankshaft is turned, the engine is damaged. Check for cleanliness with the endoscope; repeat cleaning if necessary.
Then clean the intake port and intake valves with BMW Brake Cleaner 3.3 and dry thoroughly with compressed air.
Explosion hazard/risk of fire: Do not operate vacuum cleaners with flammable liquids.
As soon as it is ensured that all granules have been removed from the above-mentioned areas of the cleaned cylinder, close the intake port on the cylinder just cleaned and install the SPARK PLUG and IGNITION COIL .
Continue to turn the crankshaft at the central bolt according to the firing order of cylinder bank 1 (1-5-3-6-2-4) until the piston on cylinder 5 is just before the intake BDC. Then continue cleaning the intake valves, intake port, combustion chamber roof and piston crown according to the instructions above.
Cylinder bank 2 is cleaned in the same way as cylinder bank 1 and starts at cylinder 7.
Firing order, cylinder bank 2: (7-11-9-12-8-10).
When cleaning is complete on all cylinders, remove all seal plugs, check pipes, openings, sealing and functional surfaces for any foreign bodies or contamination; clean if necessary.
Reassemble the vehicle.
After conclusion of the cleaning and installation work:
- Commissioning service function after walnut blasting
Here is the recommendation for engine start after cleaning the combustion chamber:
- Start the engine and press on the accelerator pedal several times quickly and deeply immediately after the engine has started.
- If the engine runs smoothly on all cylinders, the mixture adaptations are deleted. Carry out quick test; make sure that no entries are stored about misfiring.
- Engine running is OK: Process successfully completed.
- Engine is not running smoothly: Turn off ignition and wait 5 - 10 minutes so that the engine oil pressure is completely reduced before the next engine start.
- Start the engine and press on the accelerator pedal again several times quickly and deeply immediately after the engine has started.
- Engine running is OK: Delete mixture adaptation. Carry out quick test; make sure that no entries are stored about misfiring. If everything is OK, the process has been successfully completed.
- Engine is not running smoothly: Allow the engine to warm up to operating temperature when idling (15 - 20 minutes) - even if not all cylinders are running (fuel injection is switched off to the affected cylinders).
Once the engine has reached operating temperature, turn off the ignition and wait at least 15 minutes - no more than 60 minutes. (Now that operating temperature has been reached, meaning that the oil has low viscosity, the hydraulic valve clearance compensating elements gradually move back to their previous positions and the valves close correctly again.
- Start the engine and press on the accelerator pedal several times quickly and deeply immediately after the engine has started. Now all cylinders should run. Clear fault memory, delete mixture adaptation.
If the engine is still not running smoothly, turn off the ignition and wait at least 15 minutes until the next engine start. If after this the engine is still not running smoothly (the malfunction indicator lamp is lit), perform a cylinder compression test. Should the cylinder compression test be abnormal with leaking valves as the cause, it is very likely that not all granules were removed from the respective combustion chamber or the intake port and the valves on the affected cylinder are damaged. Repair engine.
Only after prolonged engine operation under all customer-relevant conditions (e.g. higher RPMs, greater loads, longer overrun phases) and a subsequent cold start can it be ensured that the engine is absolutely trouble-free.