The M30 engine is one BMW’s long run power plants. From a performance standpoint, its also one of the more common engine swaps performed to replace some of the lesser powered late 80’s and early 90’s BMWs. Most have stood the test of time with only minor valve adjustments and routine services. Hence, the term “bullet proof” is associated with this torque monster.
Head gasket replacement is one of these DIY jobs which usually are performed due to age of the car. There are a few variations of the M30 engine. Though my example for his DIY is a M30B35 from a 1989 E34 BMW 5-Series. The job is relatively the same for all M30 variants.
Performing a head gasket service comes across as being more intimidating than the actual job. With the right tools, a repair manual, some tricks and mistakes I will share. You’ll be more comfortable doing the job.
Necessities for the Job
Here are the things you will need to perform this job:
8mm,10mm, 15mm, 18mm, 19mm, & 36mm socket
Spark plug tool or socket
3mm, 5mm & 6mm allen key
1/4″ socket wrench
1/2″ socket wrench
Torque wrench
Breaker bar
Fan clutch wrench
32 mm crescent wrench
Flathead & philips head screw drivers (varying length)
Masking tape
PB Blaster
A couple coffee cans or sandwich bags for bolts, screws and such
Oil pan
Ramps, or jack and jack stands (if you have chocks that’s good too)
Cylinder head gasket kit
Brake clean and steel wool
Some patience and a few breaks in between.
The Job
This job is a tedious endeavor which one only would want to do once or when deemed necessary. However it does open the opportunity to carry out other services. Some of these procedures aren’t necessary. However if you have a fresh cylinder head, refreshing the internals of the cylinder head itself, or sending the head out to a machine shop. It may be to your advantage to perform some of the smaller maintenance items such as distributor, spark plugs, and other items I will mention. Use the masking tape to label all the wiring, small hoses, coffee cans or sandwich bags. This will be a Godsend when putting everything back together.
Teardown
1. Raise your car up on the ramps or jack stands. On a 1989-1993 BMW 535, place your jack stands under the two center rails which run the length of the car. Some will tell you locate the jack stand on the jack points. If you have side skirts installed this can be difficult to do and could damage your skirts. So place the stands under the rails. Other M30 fitted cars may be different. So place your jacks tands were specified.
2. Disconnect the battery, engage the parking brake (emergency brake), place the car in neutral, and place a chuck or something behind the rear tires for safety.
3. Locate the drain plug at the bottom of the radiator. Using your Flat head screw driver open up the screw and drain your coolant. While there, remove the hoses from the engine to the radiator. Turn your attention up stream and remove the Coolant expansion tank from the coolant system. Then return back to the front of the car and remove the radiator. With your Flat head screwdriver remove the radiator support clips and fasteners from the radiator and fan shroud. Disconnect the temp sensor from the side of the radiator. You should now be able to lift the radiator out.
4. Position the fan clutch wrench against the water pump pulley with the bolt heads sitting in the slots in the wrench.
Using the 32mm crescent wrench turn the fan nut counterclockwise to remove the fan.
5. Remove the oil pan bolt from the oil pan and drain the oil. As well open up the oil filter canister and remove the filter. Not really necessary to remove the oil filter but if your doing a head gasket it’s a pretty good Idea to perform a oil filter service when adding fresh oil. this can be done after the job is complete for when you start the car for the first time trace amounts of debris that may have made way to the oil pan. Leave the oil catch pan under the engine for toward the end you want it to catch any fluid that may spill from the removal of the cylinderhead.
6. Remove the spark plug wires, plug wire harness and spark plugs from the head. The One plug wire has a connection to the wiring harness box located on top of the injectors. Well will get to that.Then with a 8mm socket remove the distributor cap and use the 3mm allen key to remove the 3 screws holding the rotor button. Once removed use the 6mm allen key and remove the distributor followed by the plastic cover.
7. Now begin to remove all the intake electronics and duct works. Using a flat head or Philips head screw driver to release the hose clamps. Use a 10mm open end wrench to remove the nuts holding the AFM mounting bracket from the valve cover. You should now be able to unplug and remove the AFM, ICV, and valve breather hose. In doing so you can also remove the connections to the 2 coolant temperature sensors and the TPS.
8. Using a 10mm socket, remove all the nuts and the one screw from the valve cover. The valve cover should be free to remove as well as the valve cover gasket. You save this for later but I like moving from one side to the next. So it’s your decision if you want to do this step now or wait till your close to removal.
9. Take your 5mm allen key/wrench and remove the screws from the wiring harness box. There are several connections to other items however at this point most have been removed except for the crank position sensor, the one plug wire pulse connection and the oil temperature sensor. Go ahead and remove them from the wiring harness box or the oil temp sensor. Carefully pull up on the wiring box to release the injectors from their connections. At this point you should have an open view of the head and the fuel line. Using a flathead screw driver you should be able to remove the ICV pipe which is connected to the Intake. It’s a little tight for room so you can try to do remove it at this point or when you remove the fuel line and injectors.
10. Using your 10mm socket remove the screws holding the fuel rail in place. DO NOT disconnect the fuel rail yet. The rail is under pressure. You’re going to need plenty of rags to pick up the wasted fuel. We’re going to focus our attention to the other side of the engine.
11. There are 3 fasteners holding the support bracket in place. Two 13mm nuts connecting to the intake manifold and at the foot of the bracket a 13 or 15mm bolt. As you remove the 2 nuts you will see the fuel line bracket. As you remove the nut the bracket will come off with it . This is ok. we will be tackling that next.
12. Remove the charcoal canister line from the intake manifold by freeing it from the underside of the manifold closest to the head under the ICV pipe flange. While your hand is under there, reach toward your right and remove the vacuum line. With those out the way go ahead and disconnect the starter wires. Though the wires are sized differently it’s ok to label them with the tape.
13. Remove the brake booster line from the manifold. From there twist and disconnect the O2 sensor. Also go ahead and remove the throttle cables and assembly from the intake manifold and throttle body. Be sure to use the tape to remember which cable is which.
14. The gas lines from the filter and tank are held to the fuel rail by two small screw clamps. Label which is the return and which is the send. These two lines if confused will mimic other issues. As a result you may end up chasing your tail for a while. (I did it) Remove the lines and you should now be ready to remove the rail.
15. Turning our attention back to the right side of the car. Go ahead and remove thermostat and thermostat housing. There are three 13mm nuts holding it on to the head. You will have to remove the piping which connects to the water pump if you haven’t removed it prior. Once the piping is removed you should be able to access all the nuts and remove the housing.
16. If you chose to wait to remove the valve cover and gasket (step 8) do so now. For we’re going to remove the upper timing chain cover and gasket. With your 10mm socket and 10mm open end wrench remove the 6 bolts holding it to the cylinder head. Remove the upper timing chain gasket. With both covers off you are now ready to set the engine to Top Dead Center or TDC.
17. As stated in step 2, make sure your car is in neutral and parking brake (Emergency Brake) is up and engaged before turning the crank. On the Balancer you will see a tick paired with the Letters T and O. When aligned with the raised pointer or line on the lower timing chain cover the motor will be at Top Dead Center (TDC). You have to rotate the crank to align both marks. Now using your 36mm socket and a 1/2 socket wrench turn the crank clockwise till both are matched up.
18. Once TDC has been achieved we turn our attention to the cam sprocket. We have to remove the sprocket in order to clear the timing chain from the head. This will require the timing chain to be lifted from the camshaft. You can remover the chain tensioner. It’s not necessary step, but It does make moving the chain a bit easier.
Be careful to secure the chain to the sprocket and take up any slack. If this is deviated, dropping the chain into the engine is highly probable and will extend your time on this job. Using string, speaker wire or zip ties to secure the chain to the sprocket. Once secured remove the 10mm bolts holding the sprocket to the camshaft. Carefully lift the sprocket off the camshaft. As a safety net, I usually the sprocket up and away from the head. This way I not only take up any slack, I also get it out of the way to make the job a bit easier.
19. At this point your just about ready to remove the head bolts and lift the head off the block. However you have to remove the exhaust piping from the head. You have a decision to make. You have to decide whether to remove the exhaust piping or the entire exhaust system. In my opinion removing the exhaust system instead of just the pipes is much easier. This is also a great if your planning on replacing the manifold gaskets. Using a 15mm socket remove the nuts from the exhaust manifolds and carefully remove the manifolds from the head. The manifold are not light and can possibly damage a aged exhaust system. So you may want to secure them via string or take a wooden block and prop them up.
If you choose to remove the exhaust piping there are two nuts per pipe. Spray them with PB Blaster let them sock for 15 minutes for more stubborn nuts saturate the nuts again and allow more time for the spray to penetrate . With a 15 mm socket remove the nuts to release the downpipes.
20. Removing the head bolts will require the use of a 19mm socket and a breaker bar. Some say you can remove the head bolts in no particular order. I remove them in the order which is described in my manual which is similar to the documentation usually included with the head gasket kit. Using a sharpe marker I write the order on each location as I remove the bolts. This is good tip in case I loose track , step away from the project, or misplace the documentation I can return to it with less trouble or confusion.
21. Exhaust system removed, head bolts removed, you can now lift the head from the block. Here again you have a decision. the head is a bit heavy and maneuvering it out of the car can be tough. Using the intake manifold or the exhaust manifold will make this more simplistic. I recommend you leave the intake manifold attached to help give you leverage. If you did not remove the exhaust manifold you should do so now. Like wise, if you left the exhaust manifolds remove the intake manifold. Removing the intake manifold will require a 13mm socket an a 13mm open end wrench to remove all 12 nuts. Once you’ve chosen which to remove and done so, use a rubber mallet and a 2×4 wooden plank and tap the side of the head to break it free from the block.
22. Once free carefully lift the cylinderhead from the block. Small amounts of coolant and oil will spill so again make sure you have something to catch the fluids as well as some rags to clean up the mess. Any coolant which spilled from the head into the cylinder bores usually find their way into the oil pan. However try and soak up as much as possible with rags. I actually had a shop vac which I modified with a small 2 ft long hose and duct tape to suck up the fluid dropped into the block via passages and on top of the pistons. As well I made sure I left the oil plug off to drain anything the vacuum missed. From this point you can remove the intake manifold or exhaust manifold depending on which you used for leverage.
23. Remove the old head gasket from the block and clean up any remains stuck on the block surface. With the head out you can clean the surface of the block and any carbon deposits on the piston heads. If you have OCD you’re going to have a ball. However this is where things get tricky and becomes a matter of opinion. I found that using Brake clean and mild gauge steel wool like non detergent (No soap in the core) Chore boy are the best to remove the carbon deposits and residue left on the pistons and block surfaces. This also works true for cleaning the valve recesses and mating surface on the bottom head. We aren’t going for a polished look, just a clean surface. As a note remember to tape off the passages and chambers in the block so nothing gets in there. Cleaning the mating surfaces, pistons and valve recesses are real knuckle busting work so plan to take a few breaks in between. Again there are numerous DIY’s on head, block, and piston cleaning. So find one that you’re comfortable with.
24. All clean and free of deposits you now can either send the head out to a machine shop for further work or you can replace the head gasket. From my experience I seldom seen a m30 head that is warped beyond spec. This is not to say this doesn’t occur. However the M30 variants have a tolerance much higher than other cylinder heads. That said you can use a carpenter’s level to make sure there is no uneven surface area on the head. If you do happen to find that the head is out of spec, I suggest to have a machinist perform the necessary work.
25. With the new gasket in position on the block you can now reassemble the engine. Carefully reinstall the head onto the block. Did you remember the head bolt sequence? If not refer back to documentation and the marks you left on the head. To torque down the head bolts you have to do it in a 3 step process.
1st session: 50 Nm / 37lb-ft
2nd session: 80 Nm / 59 lb-ft
From here you have to wait 15 minutes or so for the bolts to set then the final session : 100 Nm / 74 lb-ft
26. Cylinder head now fastened to the block, You now can finish putting everything back together with their associated gaskets.
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About the author: William Yelder
William is an enthusiast, entrepreneur, and BMWCCA member from Freehold, NJ. Preferring the classic lines over modern convenience, he’s continuously improving the performance of his ’95 BMW 5-Series, One bolt at a time.