Does your BMW have a burning smell when you’re sitting in traffic? Have you noticed oil spots in your garage or driveway? You may have a leaking valve cover gasket.
The valve cover is a part that goes over the top of the cylinder head, keeping oil in and dirt out. In some engines it covers the timing chain too. Between the cover and the cylinder head there’s a gasket that seals the joint.
On many European engines, especially some four and six cylinder BMW units, these gaskets start leaking after a few years. If yours is doing this it’s not something to panic about. However, neither is it a job to put off for long. Before you rush in to your favorite BMW repair specialist here’s more about the problem and how we solve it.
Purpose of the Valve Cover Gasket
In a complex assembly like an engine you can’t just screw parts together and expect oil not to seep through the joint. This is because temperature changes make everything expand and contract, including the screws holding the parts together.
To handle this the manufacturer puts a gasket between the two surfaces. This is made from a compressible, slightly springy material that ensures the joint is kept completely sealed whatever the temperature.
In a valve cover gasket like those used by BMW this material is an oil-resistant elastomer. It starts out soft but over time becomes harder and less flexible and eventually begins to leak.
Symptoms of a Valve Cover Leak
What usually prompts the owner to seek some advice is a burning smell. Typically it will be strongest when the engine’s hot and the car isn’t moving.
This smell is caused by oil dripping onto the exhaust manifold. If you do nothing about it the oil will spread further and make a big mess. It’s particularly problematic when it gets onto hoses because it can attack the hose material. Ignore the problem too long and you will eventually find oil on your garage floor or driveway.
The BMW Valve Cover Repair Process
Although the valve cover is at the top of the engine there are other parts in the way. These need to be disconnected and/or removed first. Depending on the model, they will include strut tower bracing, various hoses, ignition coils and the air intake tube.
With the cover revealed, you remove the fasteners holding it to the cylinder head and then pry it away. The gasket itself will probably fall out of the cover, most likely in pieces if it’s become brittle.
Next, both surfaces – valve cover and cylinder head – need thorough cleaning to remove any traces of dirt that might cause a poor seal. Then the new gasket is installed into the cover and the cover fitted back on the cylinder head.
Note that in some engines there are spark plug tube seals and sensor seals to replace along with the gasket.
It’s very important that valve cover screws are tightened to the correct torque. Too tight and the cover may distort and leak. (Most covers are made from plastic.) Not tight enough and yes, it will leak.
Then reinstall everything that came off the engine, top off the fluids, and start it up. At EurAuto we give every valve cover repair job a short test drive to get everything up to temperature before re-checking for leaks.
Let Us Handle Your Plano, TX BMW Repair
Replacing a valve cover gasket is a straightforward BMW repair, but because of the number of parts that have to come off and go back on, it’s not a quick job.
To schedule an appointment, call us at (214) 552-4194 or use our online scheduling form.