[click to enlarge]
One of the more common oil leaks
on BMW engines is the large, long valve cover gasket. In general,
it's pretty easy to remove and replace this gasket. This article
goes over in detail the procedure to replace the valve cover gasket.
Begin by prepping the car. The only thing that you really need to do
is to make sure that the car is cold. If you try to remove or
install spark plugs in a hot car, then you may encounter problems with the
spark plugs gumming up or damaging the relatively delicate threads in the
aluminum cylinder head. Just make sure that the car is cold, or at
the bare minimum, only slightly warm to the touch.
Let's talk about the six
cylinder cars first. The first step is to remove the top plastic
covers from the engine. These serve no mechanical purpose - they are
there only for decoration and to prevent dust and debris from getting into
the recesses of the engine. On the six cylinder cars, there are two
covers, a long thin one on the top of the car, and a wider one towards the
left. Speaking of left, for the purpose of this particular tech
article, I will refer to the left side of the engine as being on the left
as you are standing in front of the car looking at the engine. The
right side would, of course, be opposite to that. For reference, the
windshield washer bottle would then be on the left, and the air filter
would be on the right.
On the two plastic covers, there
will be two small, snap-in plugs on the top. Carefully remove these
plugs (don't drop them into the engine) with a small screwdriver, prying
them up as you grab them (Figure
1). Underneath you will find a nut that holds the cover onto the
top of the engine (Figure
2). Remove the four nuts on these two covers, and they should
both simply slide up out of the way.
Figure 3 shows the engine with the center cover removed.
Underneath the left cover, you
will see the six spark plug coils that sit on top of each of the plugs (Figure
4). You need to remove each of these carefully, in order to gain
access to the plugs. Using a screwdriver, release each connector
from each coil. There is a metal retaining ring on the rear of each
one that fastens it to the coil (Figure
5). Once you lift up on the retaining clip, then the connector
should simply slide out of the coil. Carefully remove all of the
connectors from each coil (Figure
6), taking care not to bend the wire harness too much. These
wires are stiff, and generally don't take well to being bent in multiple
directions. Just be gentle with them.
To assist with your maneuvering of the wires, detach the center clip that
holds the wires that come from the center channel. This clip is
Figure 7. Gently place the wires off to the side and out of the
way, without bending them terribly.
With the wires detached and placed slightly out of the way, you can now
remove each of the six coils. Each coil is fastened to the valve
cover using two screws. On two of the coils, there are two small
ground straps that connect the coil to the stud on the cylinder head.
Take note of these ground straps - they must be installed properly when
you are finished, otherwise your car may encounter problems. These
two ground straps are shown marked by the greens arrow in
Figure 8 and
(coil already removed in this photo).
Remove each of the two nuts that
hold each coil to the valve cover. At this point, the coil should be
able to be easily pulled right off of the engine (Figure
10). The coil has a small coil pack on one end, and a
spring-loaded spark plug connector on the opposite end. Simply
remove the coil/plug assembly and place it off to the side. All of
the coils are the same, so it doesn't matter which cylinder bank it came
off of - unless you are specifically trying to troubleshoot a bad coil
fault code that was displayed by the main computer.
With the coils removed, you can now remove the top plastic cover on the
wire harness box that straddles the intake manifold and the valve cover (Figure
11). The lid on this box simply snaps off. With it
removed, you can then reach in so that you can carefully pull the wire
harnesses out of the way (Figure
12). At this point, you can start removing the nuts that hold
on the valve cover. Take careful note of which ones have ground
straps attached (Figure
13), and make sure that you record where they are located so that you
can put them back into their proper place when you're reassembling the
Some of the nuts may be difficult to reach, in particular the one located
all the way at the rear of the engine compartment underneath the
windshield wipers (Figure
14). A small ratchet comes in handy here. When you have
removed all of the nuts (there should be 15 of them), take a rubber
mallet and tap the side of the valve cover to loosen it off of its gasket
You should then be able to remove the valve cover.
Inspect the valve cover when it comes off. In particular, be careful
with the baffle and seal on the inside (Figure
16). This seal does not appear to be available as a separate
part (it comes with the valve cover). The good news is that it
doesn't really do much - it just seals an air baffle to the valve cover.
Also, when you remove the valve cover, make sure that you don't loose any
of the rubber grommets (Figure
17), or flat washers that hold them in.
If you take your valve cover into your machine shop to be sand blasted,
make sure that you assemble all of the bits and pieces back together in
their proper order. Especially important are the rubber studs that
hold on the top plastic covers (Figure 18), as well as the baffle on the
inside of the cover (Figure
Prep both the surface of the cylinder head and the valve cover for the new
seal by carefully cleaning all remnants of the old seal off of all of the
mating surfaces. Be careful not to scratch any surfaces, and also be
careful not to drop bits of pieces of the gasket into your engine.
The BMW factory manuals recommend adding some sealant to some leak-prone
sections of the cylinder head. I chose to use Permatex High-Temp
RTV, and it worked very well for sealing these areas. Specifically,
the factory recommends adding sealant at the interface where the VANOS
unit or front mounting timing chain cover meet (Figure
Figure 20). They also recommend a small bit of sealant at the
rear of the cover (Figure
With the sealant
attached, simply place the new gasket on the cylinder head (Figure
22). Place the two inner gaskets on the spark plugs holes in
center of the head (Figure
23). These are the gaskets that leak oil into the spark plug
holes (see the
Pelican Parts Technical Article on Replacing Your Spark Plugs).
Finally, bolt down the cover, and reattach all off the nuts on the cover,
making sure that you replace the rubber washers/bumpers under each one.
Using a torque wrench, tighten the nuts down to 89 in-lb (10 Nm).
shows the finished product.
If you haven't
replaced your spark plugs, now is a good time to do it. See the
spark plug replacement article for more details. Reinstall the
coils, reattach the wire harness, and replace the top plastic covers.
Well, there you have it - it's
really not too difficult at all. If you would like to see
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