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6-Cylinder Crankcase Breather Hoses and Covers Replacement
 
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Pelican Technical Article:

6-Cylinder Crankcase Breather Hoses and Covers Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$300

Talent:

*****

Tools:

T25, T30 Torx, E10 Inverted Torx, flathead screwdriver

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Crankcase breather hoses, silicone

Hot Tip:

Work with a cool engine

Performance Gain:

Remedy oil leaks and drivability issues

Complementary Modification:

Replace spark plugs and wires

Every internal combustion engine produces "blow-by" as compression leaks slip past the piston's sealing rings. High mileage engines may produce more of these crankcase gases. These gases have harmful emissions and cannot be allowed to pass into the atmosphere. These gases are recirculated by being drawn into the intake of the engine through a PCV system. Crankcase gases are sent to an oil separator, which allows liquid oil to drain back to the oil pan and allows only the crankcase gases to continue through the valve into the intake system.

When a crankcase breather hoses fail, engine drivability suffers. You may have a rough idle, hard start or a check engine light that is ON with fuel trim faults. If you have a check engine light related to the mass air flow sensor or fuel trim, inspect the crankcase breather hoses and covers first. If a leak is present, the DME may flag fault codes in systems related to air measurement. In this tech article I will show you how to replace the crankcase breather hoses and the crankcase breather covers that sit on top of the valve covers.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Crankcase breather cover leaks are sometimes mistaken for valve cover gasket leaks.
Figure 1

Crankcase breather cover leaks are sometimes mistaken for valve cover gasket leaks. Inspect the top area of the valve cover and around the breather cover (red arrow) for signs of oil leaking. This photo shows the ignition coils removed. You can see the oil gathering under and around the breather cover, indicating the seal has failed.

Working at the engine cover (red arrow), pull off the two front sir duct hoses (green arrows).
Figure 2

Working at the engine cover (red arrow), pull off the two front sir duct hoses (green arrows).

To detach the ducts, pull them straight off the engine cover / air filter housing.
Figure 3

To detach the ducts, pull them straight off the engine cover / air filter housing. Then pull the front of the duct out of the radiator support and remove it from the engine. Repeat this step for each duct.

Lift up and remove the front engine cover.
Figure 4

Lift up and remove the front engine cover.

Then, pull the engine cover / air filter housing straight up to remove it.
Figure 5

Then, pull the engine cover / air filter housing straight up to remove it. Four metal clips that grab onto rubber mounts hold on the cover, the front two are shown (red arrows). The rear of the cover has two as well. Once detached, remove the engine cover / air filter housing from the engine.

With the cover removed, you now have access to the breather hoses.
Figure 6

With the cover removed, you now have access to the breather hoses. There is one hose that runs from each breather cover to the intake manifold (red arrows) and one that runs from the breather cover to the intake air duct (green arrow).

Working at the rear of the intake manifold, pull the breather hose (red arrows) straight off the duct to remove it.
Figure 7

Working at the rear of the intake manifold, pull the breather hose (red arrows) straight off the duct to remove it.

Working at the right side valve cover, pull the breather hose straight off the breather cover to remove it.
Figure 8

Working at the right side valve cover, pull the breather hose straight off the breather cover to remove it.

Working at the rear of the intake manifold, pull the breather hose junction out of the intake manifold.
Figure 9

Working at the rear of the intake manifold, pull the breather hose junction out of the intake manifold. Pull it straight up to remove it. Once up, pull the hard line (red arrow) out of the breather hose and lay it aside.

Working at the left side valve cover, pull the breather hose (green arrow) out of the mounts running under the wiring harness holder.
Figure 10

Working at the left side valve cover, pull the breather hose (green arrow) out of the mounts running under the wiring harness holder.

Working at the left side valve cover, pull the breather hose (red arrow) straight off the breather cover to remove it.
Figure 11

Working at the left side valve cover, pull the breather hose (red arrow) straight off the breather cover to remove it.

This photo shows the breather hose assembly removed from the engine.
Figure 12

This photo shows the breather hose assembly removed from the engine. Once removed, clean the connections at the intake manifold and breather covers.

Now it's time to remove the second half of the breather hose you detached from the intake air duct (green arrow) earlier.
Figure 13

Now it's time to remove the second half of the breather hose you detached from the intake air duct (green arrow) earlier. With the smaller hose out of the way, you can sneak this one out. Pull the breather hose (red arrow) straight off the breather cover to remove it.

Then feed the breather hose out from under the wiring harness and fuel rail to remove it.
Figure 14

Then feed the breather hose out from under the wiring harness and fuel rail to remove it. If you are only replacing the hoses, you can reverse the steps to install new ones. Or continue to replace the seals on the breather covers.

With the breather hoses removed, you can now replace the seals on the breather covers.
Figure 15

With the breather hoses removed, you can now replace the seals on the breather covers. Start by removing the ignition coils. See our tech article on spark plug and ignition coil replacing. Then clean any dirt and oil residue from the valve cover.

Next, remove the two E10 breather cover fasteners (red arrows).
Figure 16

Next, remove the two E10 breather cover fasteners (red arrows). Then remove the two T25 Torx breather cover fasteners (green arrows).

With the fasteners removed, use a flathead screwdriver and lever the cover up to remove it.
Figure 17

With the fasteners removed, use a flathead screwdriver and lever the cover up to remove it. If the cover is stuck, lightly tap it with a rubber mallet to break the seal.

Once free, remove the breather cover from the valve cover.
Figure 18

Once free, remove the breather cover from the valve cover.

With the cover removed, use a plastic gasket scraper to remove the sealant from the groove in the breather cover.
Figure 19

With the cover removed, use a plastic gasket scraper to remove the sealant from the groove in the breather cover. Then remove the leftover sealant from the valve cover. Be sure both sealing surfaces are clean and free from oil and old sealant.

Fill the breather cover channel with a small bead of silicone sealant.
Figure 20

Fill the breather cover channel with a small bead of silicone sealant. Then smooth out the sealant, removing the excess and filling in any gaps. Install the breather cover to the valve cover. Then install the two T25 Torx breather cover fasteners. Once tight, install the two E10 fasteners. Reassemble the remaining items. Once the engine is reassembled, top up the engine oil. Then run the engine to be sure the leaks have been repaired.

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