How to adjust the valves on a M20 engine
In this article we will discuss adjusting the valves for the E30 6 cylinder BMW. In this case we will be using my 325i. This method applies to all M20 engine variants including 5 series BMW's. Keep in mind that this article does not apply to the E30 318i or the M3.
Why adjust the valves? You want to keep your valves adjusted as a regular part of your vehicle’s maintenance. Often times, a poorly running engine can purr like new simply by adjusting the valves. When valves do go out of adjustment, they can cause a variety of problems, such as poor fuel economy, loss of power, and even overheating. Many times, failure to adjust valves can result in the valve actually breaking off and causing major damage to the engine.
I would always adjust the valves when the engine is stone cold. If you've run the engine recently, allow at least 6 hours for it to cool before attempting adjustment.
You’ll want to begin by disconnecting the battery. This is just common sense, as you will be working around fuel lines and electrical components, and you can cause serious damage to both you and your car by failing to do this. The battery is located in the rear trunk, on the passenger side under a small access cover on the coupe's or under the bonnet on all other models.
- 1. Begin by undoing the 8 rocker cover bolts and the 4 bolts for the bracket which attaches to the inlet manifold. Also slacken the jubilee clip for the breather hose and separate the hose from the rocker cover as shown in the picture below.
- 2. Next remove the plug leads and plugs. If your leads are not already labelled then label them up, cylinders 1 to 6. The cylinder nearest the front of the car is cylinder 1.
