BMW M42 318i – Timing Case Profile Gasket


The BMW E30 and E36 3-series models (318i and 318iS of model years 1990,1991,1992, 1993, 1994) with the M42 4-cylinder engine were prone to an issue where a rubber gasket between the upper and lower timing case at the front of the engine would leak coolant, necessitating the removal of the cylinder head for replacement.


I wrote this article in 1999 when I was 16 years old and the timing case profile gasket failed on my 1991 BMW 318iS at 103,000 miles. At that time, information about it was sparse and I was a lousy writer. After a few years my site went down (I kept the HTML code) – but I was amazed at how many people e-mailed me rather consistently begging for the return of my timing case profile gasket article. So here it is!


You may have noticed that the E30 Bentley manual does not cover the M42 engine—the E36 manual does, but I was still feeling uneasy about it when faced with the prospect of taking the engine apart. That’s what this guide is for.

Here we go… first drain the coolant

Drain the coolant into a bucket that can hold at least three gallons. I used the black plastic tub in the picture. To do this, let your car cool down (overnight is best) and remove the big plastic fan cover by popping out the corner pins, sliding it up and wedging it past the fan. Then take off the radiator cap and then loosen the blue plastic screw on the driver’s side bottom of the radiator. Whether you do this from above or below the car is up to you. The coolant will start to flow out a small drain tube/hole thing close to the blue drain screw. I squeezed the tubes to get more coolant out. it is now time to take off the radiator hoses. There are only two, and undo them both. They are held on by hose clamps. I would suggest replacing these if they are the original ones. KEEP THE BUCKET under each hose when you disconnect it…I had a half gallon of coolant gush out of the lower hose opening on to the garage floor because I thought the radiator was totally drained. Next, remove the radiator by undoing the two screws on the black plastic thing at the top of the radiator. You really can’t miss them. Pull off the black plastic thing, and (quite simply) lift the radiator out of the engine bay. Don’t move it around much or you’ll get coolant all over the place. When you can access the bucket, dump the remaining coolant out of the radiator into the bucket. Have the radiator flushed out and cleaned. It is my motto that when I take something off my engine, I clean it (and the nuts and bolts too) before I reinstall it. Do the same and your engine will look brand new when you’re done.


Next remove the spark plugs…

Open the BMW tool kit in your trunk and pull out the spark plug removal tool and get a screwdriver. There are two big flat flush-mount screws in the black plastic center piece that says “B M W” on the valve cover. Twist these screws 90 degrees and they will unhook. Take the cover off and set it aside. It will be a long time until you ever put it back on. now you should see the spark plug wires. There is a little blue one-inch-long plastic grabber thing in there that you slip over the head of each spark plug wire and pop it off the spark plug. Pull them spark plug wires off carefully with your fingers. Do not pull by the wire itself. Pull on the head. Each should come out without a problem. On the passenger side, on the side of the valve cover are two nuts that hold on the small “holder” which guides the sp. wires. Undo these. Pop all four wires off the top of the (obvious) black plastic electronic ignition “box”. Your wires are now ready to be stored or replaced if need be. Put them away in a safe place. Hey remember that spark plug tool that you put together? Go get it. Stick it way down in the holes in the middle of the valve cover (as shown in photo above) and push it on ’til it “holds” on to the spark plug. Remove them. The sp tool will hold on to them for you until you take them out. Note which spark plug goes in which cylinder (I forgot to do this – it’s also a good time to replace them). Set aside the sp’s and keep going….


Radiator shroud removed (above)
Remove the air intake boot, the one that is held on by a hose clamp at each end. It is the black rubber ribbed thing about 8 inches long by 3 inches wide that goes from the end of the airbox to the throttle body. There is a tiny hose on the bottom of this, it’s probably cracked and broken and will fall right off. (I actually removed the boot before the compression test.) Anyhow, if the boot is getting old or has any tears in it, replace it (~$45). Duct tape also works if you’re a bit under budget, but it is a temporary fix for sure.

On to the throttle body. As you can see in the pic, I have removed it and am holding it in my hand. Note the car has throttle body heaters (post-recall) below the thottle body and between it and the upper intake manifold. It was simple enough to unscrew the four small bolts that hold the throttle body on. Don’t disconnect any of the throttle wires and such, you don’t need to! You have to develop an interesting skill, the removal of the throttle body from the manifold and the lower heater block at the same time. It is not something you can learn from me, you must try it yourself. It took me 15 minutes, but I got it off. There are 5 million little hoses to disconnect from the throttle body and its heater, and naturally BMW voted to place all of these hoses on the underside of it, making the job really awful. Good luck on this one. See all the little hoses underneath this area? REMEMBER where these things go, or else you’ll have a less-than-marvelous time during re-assembly. There are fuel lines under there, so trace all hoses before you disconnect them. Fuel lines, traced north, will end in the fuel rail. You don’t want to pull off the fuel lines yet.
Note how the heater block is hanging there – well, I left it there for the photo so you can see what it is. See the thin rim of metal behind it? that is one of two gaskets. There is one on each side of the heater block (I already had removed the first one.) Replace these metal gaskets, they are about two dollars a piece.


The head is going to come off. This is where we find out if the headgasket has blown because the head is warped, or if its simply an R&R of the timing case profile gasket (referred to as TCPG from here on) Now that the valve cover has been removed, inspect the cams. Mine were fine, so I moved on. The removal of the upper timing case cover is next. Remove the fan and fan clutch….yes, the big black fan unit with 6 to 8 blades. It is threaded backwards, which will be a handy fact to recall when you reinstall it. You remove it by spinning in the direction which you normally turn things to tighten them (clockwise). It is heavier than it appears so don’t drop it, that’s an easy way to snap a blade. Removing the exhaust headers was a pain on my car, good luck with it. It was awful trying to get each and every one of those 12 nuts off (above pic), but I finally did it. Notice that before I started this whole job I stuck the wrench on there to show you….see, the valve cover isn’t even off. All 12 studs pulled out of the head, but that’s ok. I numbered them so I could put them back in the exact hole they came out of. You don’t have to do this, but I did. If the studs pull out of the head, DON’T try to get the nuts off. Leave it all alone!

Remove the timing reference sensor with an allen wrench…it’s just one bolt, it’s the thing on the passgr side of the upper timing case cover which has a wire coming out of it. The round hole in the timing case cover in the pic below is where the timing reference sensor goes, and the even smaller hole next to it is where the bolt that holds it on screws into the timing case cover.


The timing ref. sensor has a magnetic tip, so when you pull it out, it will probably stick to the engine or something. Trace the lines back to the black box underneath the area where the intake manifold used to be, and pull out the plugs. To get them free, you must pull out a metal clip from the plug assembly. Hold on to it when you pry it off, or it will go flying and you’ll never see it again. Now that the wires are disconnected, just move the whole thing out of the way for now.


I’m assuming you have already removed the radiator hoses from the T-bar shaped thermostat housing ….remove the three or four bolts that hold the thermostat housing to the head, and pull it off.

You will be replacing the thermostat, so don’t be afraid to destroy it when trying to remove it. It pops right out, but it is really stuck there, most likely. I stuck a screwdriver through it and yanked about 6 times before it flew out. You should now be able to remove the upper timing case cover, unless i’ve forgotten something. You undo the numerous bolts (maybe 10 of them, see above pic to find locations of bolts) that hold the cover to the head, and then just move it around to get it off. This should expose the tensioner rail and piston. Turn the engine to TDC (top dead center). The next step I did with a friend, we marked the loactions of where things lined up, with a chisel. The cam chains, can gears, tensioner rail, etc etc. This is to ensure that the engine is all in line when reassembled. This is a very very very important part. Ensure that you do this with the utmost caution. When you are sure you can put it all back together, its time to move on.

Remove the tensioner rail piston to relieve tension on the cam chains. (You can see the dark-colored rail and its piston in the above pic, if you look between the two top fan blades. The rail looks sort of like a wide snow ski.) On the directly opposite side of the engine is an object that resembles the tenstioner rail, but it is not. It is held on by one bolt, which needs to be removed. You can see the bolt in the above pic, it is at the level of the bottom teeth on the cam gear….see it? It’s that same gold color as everything else in there. When you take it off, make note that it has an odd-looking washer-type thing on it that apparently holds the rail to the head. (I guess). It’s hard to describe. Wrap some thin wire through one of the holes at the top of each cam gear. We wrapped it around the timing chains tightly. This was to ensure that the timing of the cam gears stayed correct, as the teeth never left their original place on the chain. There are four bolts that hold each cam gear to its respective cam. Loosen these and take them out. It should be obvious from the pic to see where these bolts are. Make note of the position of them in their holes! In a star-pattern, loosen the nuts that hold down the “cam retainers” until they are out. Remove the cams and cam towers, and put them in a safe place.


You will need a TORX socket and a breaker bar for this next part…Removal of the ten headbolts. Before you do this, set aside a good clean spot where you can set the head down for inspections and repairs. Back to the headbolts: In a star-pattern, loosen each somewhat. Make a couple rounds of this, and they’ll all be out. Then pull on the head in a way as to not damage you or the head. You may have to really pull on it and break your back, but it will come off. Coolant and oil and mess will drip out everywhere, but hey, you just completed the final removal of stuff. Nothing else to really take off here, unless you want to replace the cam gears or chains….I didn’t do it because they were fine. You’ll have to learn that somewhere else.


The headgasket was great! That means I didn’t need to have the head remanufactured, because it was not warped. In fact, the TCPG (timing case profile gasket) had been blown open as far as it could be blown open, on the side facing the block. It had blown a LONG time ago….but why hadn’t it been noticed? When TCPG’s rupture, it is usually on the OTHER side of the TCPG coolant passage, facing the front of the engine. This allows coolant and oil to mix inside the timing case and it becomes a noticeable problem quickly. My TCPG blew on the side facing the block, so coolant had been spewing into the small unused chamber between the block and the lower timing case cover. as the pressure built inside this area, nothing really happened, for a while. Finally the coolant squeezed its way through to the outside between the TCPG and the headgasket, which became very noticable only a day or so before the car was officially diagnosed with a ruptured TCPG.


You will spend the next half-century getting carbon, corrosion and messy junk off the head, block, and basically anything else. I’m not kidding. Corrosion had to be scraped off the head and the TCPG area on the lower timing cover, and it was discovered that these areas had been badly pitted from the corrosion. I painstakingly picked corrosion from the head and filled in the pits with two-part heavy duty epoxy and smoothed it out with sandpaper. VOILA! the pits are gone! Did the same thing with the lower timing case cover… it’s all smoothed out. I now know why this car’s TCPG had blown….corrosion from the coolant had eaten away at it, and if this was the car’s second TCPG, the previous people didn’t even bother to scrape away the corrosion, leaving the second gasket as a ticking time-bomb.

I used air tools to clean up the surface of the head and the block, and to blow out coolant and oil passages of any guck that might be residing in them.
You will have yourself for installation…

Because no matter how much you want me to, I can’t really help you with the installation process. Installation is the reverse of removal, so keep track of what you took off. There are only a few small things left for you to do before reassembly:

Clean up surfaces where gaskets meet, IE: the front timing case cover is going to have chunks of old gasket, oil/etc depending on where you have placed it after removal. I took a chisel (shhhh, don’t tell my dad I took his prized chisel) and easily scraped this stuff off. BE CAREFUL. If you nick something, the game is over. Clean the area, and use a little sealant to hold the gaskets on.

For instance, on the front upper timing case cover, there are three gaskets (look the picture above!) One on the left “wall”, one on the right “wall” and a out-of-round one in the center. In short, get all this stuff ready.

Remove the coolant drain bolt on the engine block, right below cyl#4 header tube. Put your coolant bucket under it, a lot of coolant is going to come out. Clean up the mess (there will be a mess) and replace the drain bolt and its washer.

That should be it for pre-installation stuff. The Installation Process:

Take the head and put the camshaft towers in place. Oil the lower camshaft bearings with motor oil and lower the cam into place. Put the upper bearings in place (also lubricated with motor oil) and tighten them down according to the specs in the Bentley book. Do this with the other cam also. Assuming you have scraped all the corrosion away from the TCPG area, lay contact adhesive down in the area where the TCPG rests lowest…IE: the little valley in there. Stick the TCPG on there and remove it for 30 sec and then place it back down. Get it in there correctly, as this is the crucial step (kind of like everything else). Place the headgasket in place. Put the head on the block and slip the headbolt washers into their recesses. Insert headbolts. Torque the head to correct specs (three stages). attach cam gears to the camgear flanges and tighten cam bolts according to book specs. Remember to line it up with the tickmarks you made earlier, to ensure you do not lose timing. insert and tighten bolt on cam chain rail on drivers side. Line up tensioner on passenger side and tighten the tensioner piston to take up any slack in the chain. Attach upper front timing case cover. Attach thermostat and thermostat housing. Attach lower intake manifold setup. Note where which hoses go. Attach the exhaust headers. Have a cold beer after they are done, they are horrible (the headers, not the beer). One bolt got cross-threaded and the nut started turning, so I tightened down that nut and it was ok. No biggie. You will have to use a ton of WD-40 here, but again, no biggie. Set up upper intake manifold and accessories/tubes like that. Install valve cover and all its little rubber gaskets/pieces. Install radiator and hoses. Install throttle body and its 18 million little hoses. Install air intake system. Fill up coolant and oil. Cross your fingers. Turn the key. It will gag and sputter for maybe 20 seconds and then it will come to life. I had weird idle problems for a day or two, maybe three. It evened out and ran great after that!