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How to remove sludge (de-sludge) the engine cylinder head

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  • OVERALL DIFFICULTY INDEX: 6/10
  • IF YOU HAVE NO TOOLS, YOU PAY $35 TO GET THEM FOR THIS JOB
  • IF YOU HAVE NO EXPERIENCE YOU SPEND 8 HOURS TO CARRY OUT THIS JOB
  • SAFETY: USED OIL ALLERGY RISK, BURNS.

BEFORE YOU START
  • The below method is valid for engines with a relative low mileage and should not be used for old engines or after hundreds of thousands of kilometers.
  • It requires high experience and a lot of caution as it is performed without the removal of the engine head. 
  • Make sure to keep rubber or disposabe gloves at hand and keep changing them to avoid oil contact with skin.  
DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.

Context

​Modern downsized engines require specific oils and high quality fuels. If you missed the chance to use the adequate synthetic oil or if the fuel in your country is not that good, there is a good chance your engine cover fills with soft carbon deposits and thickened oil (sludge). The engine internal ventilation will get clogged and thermal transfer will be impacted resulting in higher operating temperatures. It's time to intervene...
The below works concerned a Peugeot 5008 equipped with a turbo-charged PSA BMW EP6 engine.
Same or similar engine and turbos can be found on Peugeot 207, 208, 308, 508, 3008, 5008 and Citroen C4, C4 Sedan, DS3, DS4, DS5 also the Mini Cooper S.

Cylinder head manual de-sludging pictorial

1- Start by removing all air hoses, oil vapor hoses, etc. that connect to the cover.
2- Carefully remove clips and harnesses, pull them aside.   
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3- Remove the ignition coils.

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4- Unscrew the many bolts that hold the cover and remove the cover.​
5- The head is black...
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6- ...a close-up shows the accumulated sludge.
7- The cover is almost clogged. 

   
8- Make a first test with your hand to make sure the thickened and carbonized oil can be easily removed.
9- Make a second test with a cotton cloth. It should absorb the oil and become wet.
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10- Start the difficult task of having the cloth passing between the cams and the head's body.
11- Because cloth towels are discarded when saturated, prepare all cotton workshop towels and/or old underwear you have.
12- Use a brush as a support to wrap the towel and clean. Never use the brush alone as this will send the dirt to the crankcase.
13- A screwdriver wrapped with the cloth will be used for tiny spaces.
14- You should be done after a couple f hours. Time now for the cleanliness test.
15- Make a first pass with a top clean towel.
16- And a second one.
17- The head is now metal brilliant. Remaining thin deposits in corners will be dealt with in the last step.
18- You may now use diesel to clean the cover. if you think this is too difficult or time consuming, you can chose to replace it with a new one.  
19- Carburetor/sensor cleaner will be used to dissolve gum on the sensors and the breather.
20- Remove the obstruction diaphragm of the breather valve and spray inside the channels.
21- When done, flip the cover right and left to make sure the oil breather valve moves freely.
22- Prepare a set of new cover gaskets.
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23- Refit all elements.
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24- Change your oil filter. This is mandatory prior to flushing the engine.

Final step of desludging: flushing the engine

25- Flush the engine, then change oil and filter (again). Use synthetic oil to the viscosity that matches your engine recommendations. Check both vehicle and oil manufacturer's data to confirm the choice and note well the newest recommendation. Double the frequency of your air filter change.

If you wish to replace the whole cylinder-head or at least the rocker gear cover, you may buy your parts from our partners:

See also our complete EP6 engine repair manual:

And more DIY tips for all types of cars: