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Replacing A Leaking Valve Cover Gasket On Your BMW.

November 20, 2009

Leaking valve cover gaskets are fairly common on BMWs. These leaks can be more than just a messy inconvenience: a leaking valve cover gasket can cause a vacuum leak, which creates problems with the engine management system. Additionally, oil commonly leaks into the spark plug wells causing deterioration of the spark plug connector boots and arcing of the ignition spark, which creates ignition miss-fires.  (A common cause for a fault code of “random miss-fires” is oil in the spark plug wells.) Replacement of BMW valve cover gaskets can be relatively quick and easy on most models through the ‘80s and into the early ‘90s. On the 6- and 8-cylinder models from the early ‘90s on, it may require a bit more work but is still not terribly difficult.

The obvious clues to a leaking valve cover gasket are signs of external oil leakage or, in the case of the later 6- and 8-cylinder engines, oil in the spark plug wells, which you may find while performing a spark plug change (see Summer 2007 Fast Times). On the early 4- and 6-cylinder engines (those with distributor caps and regular spark plug ignition wires), you simply remove the nuts securing the valve cover and lift it off. (You may have to first remove the intake air filter or a bracket or two.) The later “coil-on-plug” applications (6- and 8-cylinder models from early ‘90s on) require that the coils be removed prior to the valve cover removal. In this article we’re replacing the valve cover gaskets on a V8  (2000 740i) . (Replacement on the 6-cylinder models is similar, but you have only one valve cover.)

1. If there is a positive jumper terminal on one of the valve covers, disconnect the negative battery cable at the battery.
2. Remove the center engine trim cover. Push down on each of the four button heads and pull up on the cover at each corner (figure 1).

BMW valve cover
3. Remove the left and right trim covers by prying out the two plugs covering the securing nuts on each cover, and then removing the nuts. Pull off the covers (figure 2).

BMW valve Cover

4. Remove the positive jumper terminal on the driver side valve cover (if installed) and set aside (figure 3).

figure3
5. Release the securing clips and pull the harness plugs from the ignition coils (figure 4).

figure4
6. Remove the two nuts on each coil and pull the coils out. Either mark the coils or lay them out in the installed order (for reassembly). Note the oil on the connector boots of this engine (figure 5).

figure5 They should be completely dry. This is why we are replacing the valve cover gaskets.
7. Release the securing clips and remove the cover from the coil and injector wiring box (figure 6).

figure6
8. Gently pull the various harnesses (with the rubber grommets) out of the cutouts in the wiring box and let them lie in place. (You will need to do this for access to the injector harness plug clips in the next step.) You do not need to pull out the coil plug harnesses.

9. The wiring box sits on top of the fuel injector electrical plugs; the injector harness plugs are assembled as part of the box. In order to remove the box, we must unclip the injector harness plugs and pull the complete box up and off of the injectors. Locate the wire clips on each of the injector harness plugs, under the wiring box. Use a pick or small screwdriver to pull out (dislocate) one side of the wire clip on each plug housing (figures 7 & 8).

figure7figure8 Once all of the clips are dislodged, we can pull the box up and off of the injectors. Lay the box and wiring over the intake manifold.

10. Remove the nuts/bolts securing the valve cover (here 8 nuts and 3 bolts). Pull the valve cover up and off. It may be necessary to remove the two bolts holding the power steering reservoir and push it aside. You may also have to gently insert a pry tool at the gasket, between the valve cover and the cylinder head, to release the cover (figure 9).

figure9
11. Remove old gaskets from the valve cover. Thoroughly clean the cylinder head mating surfaces and valve cover gasket surfaces. (This may require scraping, especially on the valve cover.) Using a clean rag, finish cleaning with a non-petroleum based cleaner (e.g. Wurth brake parts cleaner).
12. Apply the new gaskets to the valve cover. ONLY use sealant on the cam cutout fillers on the gasket, as shown (figure 10).

figure10 We use Permatex Ultra Rubber Gasket Sealant and Dressing. (The manuals call for 3-Bond 1209 or equivalent.) While the sealant is curing, remove the spark plugs and either replace them (if needed) or clean the oil from them (figure 11).

figure11 Insert a clean rag into the spark plug wells (in the cylinder head) and clean out the accumulated oil. Install the spark plugs.

13. Install the valve cover being careful to properly seat the cam cutout fillers on the cylinder head cutouts. Once you have the cover seated, feel around the back of the cover and head to verify that the cutout fillers are seated properly. Install the new rubber seals, bolts and nuts. Torque the fasteners in a spiral or criss-cross pattern, to the value specified in the applicable manual.

14. Finish the installation of all remaining parts. Note that the wire clips on the injector plugs need to be in the dislodged position in order to fully seat the plugs and the box. Once the plugs and the box are seated, you can use your pick to re-seat the clips.

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