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 | BMW 3-Series E30 |
Difficulty Level: 4 |
| This article is the one in a series that will be released in conjunction with Wayne's upcoming book, 101 Projects for Your BMW 3-Series. The book will be 256 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 350+ full-color glossy photos accompanying extensive step-by-step procedures, this book should be a staple in any 3-Series owner's collection. See The Official Book Website for more details. The book is due out in October 2005. | |
[click to enlarge] | In this article we will discuss adjusting the valves for the E30 BMW. In this case we will be using my 325is. It also applies to the 325i, iX and iC (cabriolet) as well as the earlier 325, e, and es models. This article will also apply to BMW 5 Series models with the M20 2.7 and 2.5 engines. Keep in mind that this article does not apply to the E30 318i or the M3, (articles coming soon). 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. An example can be seen here. The Bentley manual says the valve clearances can be adjusted with the engine cold or hot. Personally I prefer to do the adjustment with the engine cold, with the metal cold, the valves have not expanded due to heat and this, I believe will yield a truer clearance reading. However, that’s just my two cents. All the Porsches need to have their valves adjusted when the engine is stone cold. 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. | |
| The next step in adjusting your valves is to open the hood, and look on the passenger side of the engine (Figure 1). You will notice the spark plug wires and the valve cover. It’s recommended that you remove the spark plugs in order to make rotating the engine easier. Start by disconnecting the spark plug leads from the spark plugs. You will want to grab the leads by the protective boots, then slowly twist them and pull, they should come right off (Figure 2). Now remove the spark plugs. You will probably need a U-joint ratchet extension to reach the plug furthest to the rear due to clearance between the block and the firewall. It’s also a good idea to stick rags or paper in the empty holes to prevent dirt or debris from entering the cylinders. The reason you will want to remove the plugs is that in order to adjust the valve clearances, you will need to rotate each cylinder of the engine to Top Dead Center (TDC). Having the piston at TDC ensures that both the intake and exhaust valves are both closed, and there will be no tension on the valves from the valve springs. With the spark plugs in the engine, the compression of the engine will make rotating the engine very difficult. With the spark plugs removed, you have no compression inside the cylinders, and the engine will rotate much easier. Once the plugs are removed, the next step is to remove the valve cover. The first step is to remove the vacuum hose that runs from the intake to the valve cover. Loosen the hose clamp, and carefully remove the hose from its fitting on the valve cover. This hose is part of the vehicle’s emission system, and it allows vapor from the crankcase to circulate back into the intake manifold. Next, remove the bracket that secures the valve cover to the intake manifold. Four 10mm bolts hold it on. Two of the bolts hold the bracket to the valve cover; the other two secure the bracket to the intake manifold. This is shown in Figure 3 and Figure 4. | |
| Once the valve cover nuts have been removed, pull the valve cover off. You may find that the valve cover seems stuck or is not moving. In this case, carefully place a flat-head screwdriver along the seam where the valve cover mounts to the head and very lightly tap it with a hammer until you have broken the seal around the valve cover. The valve cover now should simply pull off. Also remove the old valve cover gasket (Figure 6). Once the valve cover is removed, you will now see the valvetrain (Figure 7). In the center is the camshaft, and you can easily see the lobes of the cam. It is these lobes we are looking for. Look at the cam lobes at the very front of the engine, and then look at the rockers that run along these lobes. When the cam lobe hits a rocker, it pushes the rocker down, opening a valve. When the lobe rotates down, it closes the valve. You will need to have these lobes completely flat before you can adjust the valves. The way I do it is put the car in 5th gear, take off the parking brake and push the car forward. You will see the rocker arms move back and forth very slowly. Another trick is to jack up one side of the car, leaving at least one of the rear wheels on the ground, and one up in the air. With one wheel on the ground, and the car in fifth gear, you can rotate the engine by simply turning one of the wheels. This works on all cars without a limited slip differential (LSD). The idea is to look at where the rockers contact the cam lobes. When the rocker arms have stopped moving, and the cam lobes reach the lowest point on each rocker, you are at TDC. This is where you want to be (Figure 8). Now you can adjust the valve clearances on this cylinder. | |
| Look at the rocker arm; at the very end you will see where it contacts the valve. You might also notice a small space in between these two parts. This space is what we are adjusting (Figure 9). The Bentley Manual lists the correct valve clearance at 0.30mm (0.012in) with the engine hot, or 0.25mm (0.010in) with the engine cold. In this case, the engine is cold, so I adjust using a 0.25mm feeler gauge. Now, to adjust the valve clearance, you will want to find a small piece of stiff wire, such as a coat hanger or a 3mm Allen wrench. Place the stiff wire or Allen wrench in the small hole on top of the valve eccentric. In this case, I used a small screwdriver. Next, loosen the 10mm locknut on the side of the valve eccentric. This will free up the valve eccentric. Place the feeler gauge in between the valve eccentric and the valve. Now, using the stiff wire or wrench, rotate the valve eccentric til it makes contact with the feeler gauge. You want the feeler gauge to have a slight drag on it when you move it in between the eccentric and the valve. When you feel such a drag on the feeler gauge, STOP rotating the eccentric and hold it exactly where it is, and tighten the 10mm locknut on the side. Once the nut is tight, re-check the feeler gauge, does it still have a slight drag on it? If not, loosen the locknut, and re-adjust it til it is correct (Figure 10). Once you have adjusted both the exhaust and intake sides of the cylinder, you will want to take the parking brake off, and push the car in 5th gear until the cam lobes are in the proper position to adjust the second cylinder. Then repeat the process listed above for the remaining cylinders. Be sure that on every cylinder, the rocker arms are in the correct position. | |
 Figure 11 | Once the valves have all been re-adjusted, you will need to re-install the valve cover. It’s a good idea to clean the mating surfaces of both the cover and the cylinder head. This will ensure a good seal and prevent both oil and vacuum leaks. It’s a good idea to use a new valve cover gasket. To install, just place it over the studs on the cylinder head (Figure 11). Next, re-install and tighten the 10mm nuts that hold the cover to the head. Tighten them down snug, but not super tight, you could strip the nuts or threads. Next, re-install the bracket that secures the intake manifold to the valve cover and tighten the four 10mm bolts that hold it in place. Now re-install the spark plugs. It’s a good idea to put a small swipe of anti-seize compound on one side of the threads prior to installation. This will prevent stripping out the spark plugs the next time you have to remove them. Once all the plugs have been reinstalled, tighten them down, but use caution to avoid stripping threads. Next, re-install the spark plug wires, It’s a good idea to put a small dab of conductive grease on the insides of the boots, to ease installation and provide a good seal between the spark plug and the boot. The last step is to re-connect the battery. Once everything is re-installed, start the vehicle. You should now hear a smooth running engine. And that’s it, you’re done! As always, if anyone has any questions, feel free to email me at jared@pelicanparts.com Cheers, Jared This technical article is made possible solely through the support of Pelican Parts. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. | |
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