| ||This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.|
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BMW engines are known for weak cooling systems. It’s not uncommon to have a water pump fail or a thermostat get stuck, which can result in engine overheating. The car typically runs fine for a few hundred miles after overheating, but it eventually begins to leak coolant and ultimately requires a complex head gasket replacement.
This project incorporates steps and procedures from many other projects. Here are the tasks that you need to perform prior to the specific steps outlined below:
Jack up the car: Raise the front of the car to gain access to the coolant drain plug on the engine block, as well as the engine oil drain plug.
Empty engine oil: Drain out the oil that has been contaminated with engine coolant.
Remove coolant: Empty the coolant from the system prior to removing the cylinder head.
Remove radiator and fan: Remove the fan to gain access to the front of the engine. Also, remove and flush the radiator, and replace the hoses.
Remove drive belts: You will need to remove the belts in order to gain access to the water pump.
Remove water pump: You should remove the water pump in order to clean it out or replace it with an upgraded unit.
Spark plugs: Remove the ignition coils from the head, and remove the spark plugs.
Valve cover gasket: Remove the valve cover to access the head bolts.
Camshaft removal: It’s possible to replace the head gasket without removing the camshafts. However, you should have the head resurfaced by a machine shop, and this process requires that you remove the camshafts.
Intake manifold removal: The intake manifold covers a lot of items in the engine compartment and is attached to the cylinder head, so it needs to be removed.
VANOS installation/cam timing: To remove the cylinder head, you must first remove the VANOS unit. To reinstall the head, you need to retime the camshafts and properly adjust the VANOS unit.
Cam sensor replacement: Remove this sensor from the cylinder head and have a new one handy.
Crankshaft sensor replacement: This sensor is only accessible with the intake manifold off, so it might be a good time to replace it.
Tensioner update: Remove the lower chain tensioner to loosen the chain on the camshafts and upgrade to the new style if applicable.
VANOS oil line replacement: Disconnect the VANOS oil line prior to removal of the head.
Machine shop 101: Send your cylinder head out to a machine shop that will resurface it and check for cracks.
The remainder of this project is presented step–by–step in the accompanying photos and captions.
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|If you see this kind of mess with your car, you know you’re in trouble. This is a perfect example of oil mixed with coolant due to a head gasket leak. The light-colored milky texture of contaminated oil is a sure sign of head gasket problems. For a quick analysis, remove the oil filler cap and compare it to the photo (upper left). Also take note if steam comes out of your tailpipe. Some condensation is normal upon startup, but if it continues well after the car is warmed up, you have a problem. Of course, the first clue is that your low coolant warning lamp will turn on, even after filling the reservoir multiple times.|
|More carnage can be seen under the valve covers. The underside of the valve cover is coated with a mixture of coolant and oil. At this point, we’ve emptied the oil and coolant, and removed the fan, radiator, drive belts, water pump, spark plugs, and valve cover.|
|Before you remove the cylinder head, lock the engine at top dead center (TDC) for cylinder number 1 to accurately time the camshafts when you reassemble the engine. There is a special tool that needs to be inserted into a hole in the engine block, which then mates with a corresponding hole in the flywheel. The intake manifold has been removed in this photo (see our intake manifold removal article), and the yellow arrow indicates the general area where the tool needs to be inserted (see also Photo 4). You can rotate the engine’s crankshaft by placing a 22-millimeter deep socket on the front pulley and rotating clockwise (photo inset). Install the camshaft alignment tool (see our article on Camshaft Timing and Vanos Unit Installation). If your camshaft alignment tool doesn’t seem to fit, your car may have had the camshaft timing tweaked as part of a BMW service campaign to correct an uneven idle (affected engines built up to August 1992). Loosen the tool to allow it to fit in this situation.|
|Here’s a close-up of the spot in the engine case where you insert the flywheel locking tool. Your car should have a small blue plug that covers the hole (inset photo). The flywheel locking tool itself is a long, thin rod with a smaller insert tip on its end (inset, lower right). Insert this tool into the engine block and rotate the crankshaft pulley until the pin fits into the matching hole on the back side of the flywheel.|
|At TDC for cylinder number 1, the exhaust camshaft sprocket should have a small arrow that points upward, perpendicular to the plane of the head gasket. Double- check this if you’re trying to find TDC when you’re turning the engine over by hand.|
|Also check the front crankshaft pulley itself. The line by the yellow arrow will match up with the boss in the engine block (blue arrow) when the engine is at TDC for cylinder number 1 and cylinder number 6. Check the arrow on the exhaust camshaft sprocket shown in Photo 5—it should only pointing upward, not downward, when the engine is at TDC for cylinder number 1.|
|Shown here is the front of the VANOS unit prior to removal. The VANOS unit advances the camshaft timing at higher rpm, which translates into better engine performance while driving. Undo the nuts that attach the unit to the cylinder head. The cable for the crankshaft sensor (see also Project 15) is integrated with a small plastic cable guide that ties into the studs that also hold the thermostat housing and the VANOS housing (yellow arrows). Remove the thermostat in order to remove the VANOS unit.|
|With everything disconnected, you can now remove the front VANOS unit. Disconnect the VANOS oil line (blue arrow), and disconnect the electrical connection to the VANOS solenoid, as indicated by the green arrow (see our article on VANOS Oil Line & Solenoid Replacement). Remove the unit from the front of the cylinder head and place it aside on your workbench. Push the upper VANOS chain tensioner down and lock it in place with small pins (red arrow). You can use a small Allen key as shown, or even large paper clips will do.|
|Remove the sprocket assemblies from the front of each camshaft (see our article on Camshaft Timing and Vanos Unit Installation). Use a zip tie or some wire to secure the timing chain (blue arrow)—you don’t want this to fall into the recesses of the engine when you remove the cylinder head.|
|Remove the cylinder head bolts with a special BMW Torx deep socket tool (11-2-250). The bolts will be tight and difficult to remove, but if your tool is in good condition, you should have no problems removing all of them (14 total for six-cylinder engines). The bolts are hidden underneath the camshafts, so you will have to maneuver your tool past the camshafts to reach them.|
|Remove the camshaft position sensor (see photos in Project 14) and disconnect the last remaining connections to the cylinder head. The small electrical connections pull out after releasing the small spring wire retainer. Don’t forget the hose attached to the rear of the cylinder head that supplies the heater core (inset). Also disconnect and loosen the exhaust manifold (see our Exhaust Manifold Replacement article).|
|With everything disconnected, the cylinder head should be loose on the engine block. Tap it with a rubber mallet and it should start to lift off of the block. If it doesn’t budge, then chances are that you forgot to disconnect something that is holding it down. It’s not uncommon to forget to remove a cylinder head bolt. Count the cylinder head bolts and make sure that you have 14 of them prior to your removal attempt (six-cylinder engines). As the head begins to lift off of the engine block, tilt it slightly toward the exhaust manifold and grab the timing chain. Tie off the timing chain with some wire or a zip tie so it will not fall into the recesses of the engine block.|
|Shown here is the head is coming off of the engine. Untie the timing chain from the top of the head, and secure it at the top of the engine block (blue arrow). Triple-check that everything attached to the head is now disconnected. The cylinder head is very heavy, and the angle for lifting while you’re standing in front of it is very challenging. I do not recommend lifting the head off the car by yourself—get someone to help you lift the rearmost part of the head. If you attempt to lift the head off of the engine and something catches on your way up, it will be difficult to put it back down again without crushing or potentially damaging something.|
|Since you are removing the cylinder head from the engine, I recommend that you take it to a machine shop for evaluation and reconditioning (see Photo 17). Prior to taking it to the shop, you can remove the camshafts. Most machine shops won’t have the specific knowledge or the BMW factory tool to remove the camshafts safely. You can remove them yourself without the tool by following Project 11. Be careful, though—if you don’t proceed cautiously, you can bend and break the camshafts. In this photo, the long, thin BMW E36 six-cylinder camshaft has been removed from the cylinder head.|
|BMW calls this the camshaft bearing ledge; it keeps the hydraulic lifters in place and also supports and provides lubrication to the camshafts as they are running. The inset photo shows the hydraulic lifters in place. When you lift the bearing ledge out of the head, the lifters will fall out of their respective bores. Pay close attention to each lifter’s location—you’ll need to replace each lifter into its original bore to reduce wear on the bearing ledge and camshafts.|
|Here’s a close-up of the bearing ledge with the hydraulic lifters. When removing the bearing ledge, I quickly put the hydraulic lifters back into their bores so there’s no chance of misplacing or inserting any into the wrong bore. Also, keep the intake and exhaust bearing ledges separate. Although they look similar, they are very different and cannot be interchanged. With the lifters removed, clean out any sludge in the recesses of the bearing ledge. Flip the bearing ledges upside down and drop in each of the lifters. Don’t accidentally turn the bearing ledge around so the lifter that should go in one end actually goes in the other end. Take the entire assembly, with the lifters, and store it in a safe place, covered in plastic.|
|After the head is off the car, take it to your machine shop. Have the shop remove all the valves and clean it up in the bead blaster and parts washer. When the head is clean, problems like the one shown in this photo are easier to see. This particular head has a rather nasty crack in it (red arrows). Left undiscovered, this problem would have caused the replacement head gasket to fail shortly after it was installed, as coolant would have leaked around this crack. The moral of the story is that if you are doing all the work to get your cylinder head off the engine, take it to a machine shop to be inspected and freshened up.|
|The repair process is not too difficult for an experienced machinist. The area around the crack is machined out so no traces of the crack remain. After the head is preheated in an oven to several hundred degrees, the aluminum is welded and the area is filled with replacement aluminum material. Finally, the area is reground and the mating surface machined flat. In this photo, it’s difficult to see any remaining traces of the machine work, other than a few grinding scratches on the inside of the combustion chamber.|
|This is what the freshened head has returned from the machine shop. All the valves have been measured, ground, and lapped to the valve seat. The crack has been repaired, and the entire mating surface has been machined flat. Don’t forget to reinstall the oil pressure check valve on the bottom of the cylinder head. If you forget this piece, you will have engine oil pressure problems. Nothing is worse than buttoning up your entire engine—only to look over at your workbench and see this tiny check valve still sitting there.|
|A typical cylinder head gasket set. Depending on the make or model of your car, you might have one or two small sealing rings or O-rings left over. Don’t be alarmed, as this is somewhat normal. A: Front VANOS seal (metal). B: Valve cover gasket. C: Cylinder head gasket. D: Oil filter housing O-ring (small O-ring for oil filter too). E: Camshaft position sensor O-ring. F: Fuel injector O-rings: G: Valve seals and protective boots. H: Assorted copper and aluminum sealing rings. I: Rear heater core hose fitting seal. J: Intake manifold to throttle body seal. K: Thermostat housing seal. L: Exhaust manifold gaskets. M: Lower exhaust gaskets. N: Intake manifold to cylinder head seals. O: Spark plug hole seals. Additional sealing rings and O-rings: oil filter set (one tiny black O-ring, one big black O-ring, three small crush gaskets) VANOS oil line sealing rings (four), and VANOS solenoid O-ring.|
|Before mounting the cylinder head back onto the engine, clean up the engine block and pistons a bit. Using a plastic cleaning wheel attached to an electric drill, carefully brush off the dirt and debris from the cylinder head mating surface on the engine block. Do not drop any gasket material or debris into the oil or cooling ducts on the surface. First, remove the larger chunks of gasket material with a razor blade, but be sure not to scratch the mating surface. Try to get it as clean as possible. Do not spill any oil or debris into the threaded holes in the engine block where the cylinder head bolts attach. These must be kept perfectly clean, or you will not achieve the proper torque settings for the head bolts. If oil or dirt does get into these holes, clean them out with brake cleaner and lint-free cloths. To clean the tops of the pistons, remove the flywheel lock and rotate the engine until each piston is at the top of the engine block surface (inset, upper right). Then clean each one with the drill and brush. When you’re done, go over each surface with alcohol and a lint-free cloth to ensure the surface is as clean as possible, and to help prevent dirt from contaminating your head gasket.|
|If your car displayed fuel injection trouble codes prior to the head gasket problem, now would be a good time to revisit them (see Project 28 and Project 29 for instructions on reading the fault codes). There are a few sensors that are best accessed and replaced when the intake manifold has been removed, including the cam position sensor (see our cam sensor replacement article), the crankshaft position sensor (see Project 15), and the two knock sensors. This photo shows the knock sensor for cylinders 1 through 3. If you have had problems with your car knocking, or the computer has shown you a fault code for one of the two knock sensors, replace them now. They are impossible to replace with the intake manifold in place.|
|Clean each lifter carefully with a lint-free cloth. I recommend using Kimwipes, which I discovered while working in clean rooms, building satellites. You can find them at PelicanParts.com. They are perfect for cleaning intricate engine parts where you don’t want paper fibers or debris contaminating tiny oil passages. When each lifter is clean, dip it in fresh motor oil. Use whatever motor oil you plan to use when you refill the car. Press down on the inside of the lifter while it’s submerged so that you can clean out the internal passages as well as possible. (This car had its entire oil system contaminated with coolant, so it was especially important to clean everything.) Failure to do this carefully may result in what is known as a noisy lifter—one that doesn’t completely engage. This can lead to degradation in engine performance.|
|Carefully clean the inside of each lifter bore with lint-free Kimwipes Use isopropyl alcohol or brake cleaner if there is any gunk or grime you can’t remove with elbow grease alone. Soak each lifter in oil prior to putting it back into the bearing ledge. Be liberal with the engine oil, as the oil supply to the engine will be sparse when you first start it up.|
|With the bearing ledge and lifters liberally coated in engine oil, tip the cylinder head on its side and insert the lifters into the head. Make sure none of the lifters fall out of the ledge as you reinstall it onto the cylinder head. Carefully balance the head on its side while holding the bearing ledge with one hand (you should be able to do this alone). Install the intake ledge on the intake side, and the exhaust ledge on the exhaust side. When the first ledge is placed onto the head, keep it in place by installing two camshaft bearing caps on either end. When you go to install the second bearing ledge, the first one won’t fall out.|
|This photo shows the head with the camshafts installed. This installation process is tricky and can easily break the camshafts. See Project 11 for more information on removing and installing the camshafts.|
|Install the head sensors back into their respective ports with new sealing rings. If these were to leak after you start the engine, it would be necessary to remove the intake manifold again. Insert a new O-ring into the cam sensor hole. Double-check that you have properly installed the oil pressure check valve that seats into the bottom of the cylinder head (see Photo 19). If you forget to install it, you will have to tear down and remove the head all over again or you will forever have oil pressure problems with your engine.|
|Install the flange for the heater core hose onto the rear of the cylinder head. Don’t forget to reattach this hose when you reinstall the head on the engine block. Use a new gasket for this flange.|
|Clean the surface of the head and the engine block with brake cleaner and lint-free Kimwipes. If you didn’t have the cylinder head resurfaced at a machine shop (recommended), make sure that any residue from the old head gasket has been removed. The head needs to be perfectly clean in order to maintain a proper seal. Don’t skimp on the cleaning process—it is of paramount importance.|
|When the engine block is clean enough to eat off of, lay the new head gasket on the block. For machined cylinder heads, there is a 0.3-millimeter-thicker gasket available to compensate for the reduced material thickness on the head. If you don’t use this gasket, the head will be slightly closer to the pistons, and the engine will have a slightly higher compression ratio. In most cases, using the standard thickness gasket is fine (you have to buy the thicker gasket separately, as it is more expensive than the standard thickness gasket and is not included in gasket sets). Before you install the cylinder head, remove the flywheel lock and rotate the engine about 30 degrees all the pistons off the top of the engine block. Doing this prevents the valves from touching the tops of the pistons when you install the cylinder head and time the cams. This step is very important, so don’t forget or skip it.|
|Each cylinder head bolt has a special washer that goes underneath it. Use only the special washers—don’t substitute them with others. Lining the washer up with the hole can be tricky. I use a long screwdriver to help with this. Place the washer on the screwdriver. Then place the screwdriver in the hole, while holding the washer. Then let go of the washer, and it should fall down right over the hole.|
|Placing the head back on the engine block is a two-person job. As one person lowers the head, the other must thread the timing chain up through the front of the cylinder head. Do not let it drop into the recesses of the engine, as it can be difficult to fish out and align with the lower crankshaft sprocket. Once the chain is through the front of the head, tie it up with a zip tie or some wire. In this photo, the head carefully rests on top of the engine block as we manipulate the chain. After the chain is secured, move the head and locate it onto the top of the head gasket.|
|Tighten the head bolts with a calibrated torque wrench. The cylinder head bolts are a stretch-bolt design, which means they deform when tightened to their desired torque setting and should only be tightened once. If you find that you’ve forgotten to install something or made some other mistake and need to remove the cylinder head again, you must use new cylinder head bolts, since the ones that have already been tightened are no longer any good. After you tighten the cylinder head bolts, install and tighten the two small Torx bolts that attach the head to the front timing chain cover (holes shown by blue arrows on the right).|
|Shown here is the tightening order for the cylinder head. Start with the first one and work your way out to number 14. The cylinder head bolts are tightened using a special process. The bolts are tightened to a specific value, and then they are turned a number of additional degrees (typically 90 degrees). This ensures a more accurate value for tightening the bolts. For the cylinder head, torque each of the bolts up to 80 percent of the jointing torque value, following the order in this photo. Then go back in the same order and torque them up to the final jointing torque. After that, turn the torque wrench through the specified torque angle. You can find the specifications for each of the E36 engines at www.101Projects.com.|
|With the cylinder head attached to the engine block, you can now time the camshafts. First, align the camshafts at TDC and install the camshaft alignment tool (BMW tool 11-3-240). The two dots on the camshafts should face upward. Only after the camshafts have been properly aligned at TDC, move the crankshaft back to TDC and reinstall the flywheel lock pin. You are now ready to set the camshaft timing (see our article on Camshaft Timing and Vanos Unit Installation).|
|Don’t forget to attach the heater core hose to the rear of the cylinder head. If you don’t attach this hose, the coolant will spill all over the ground, and you will sit there wondering what you forgot to connect.|
|With the camshafts properly timed and the camshaft tool removed, add the engine oil. I prefer to add the oil at this point because I can pour it all over the camshafts and lifters to ensure that they are properly lubricated when I start the engine. When you’ve completed the installation and are ready to start it up, pull out the fuel injection computer (DME) relay and let the engine turn over a few times to build up oil pressure. On this particular car, I encountered a sticky lifter problem, which resulted in a “clack-clack-clack” noise when the car started up. This is normal in the first few minutes after the head gasket replacement. If the sticky lifter problem doesn’t go away, then I recommend changing your oil to a thinner viscosity. On this car, the sticky lifter refused to go away until I emptied the oil and replaced it with Mobil-1 synthetic. If the engine was highly contaminated with coolant, try changing the oil three times within the first 50 miles to flush any remnants of the coolant out of the system.|
| Looking for more photos? Click to see bonus pictures for this project.|