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Intake Manifold Replacement
 
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Pelican Technical Article:

Intake Manifold Replacement

Nick Czerula

Time:

4 hours4 hrs

Tab:

$100

Talent:

*****

Tools:

Set of sockets (8mm, 10mm, 13mm), wrenches, screwdrivers, fuel line socket

Applicable Models:

BMW Z3 Coupe/Conv (1996-02)

Parts Required:

Intake manifold gaskets, hose clamps, fuel line hose clamps, fuel line O-rings, coolant hoses and pipes

Hot Tip:

Work with a cool engine.

Performance Gain:

Smoother running engine

Complementary Modification:

Replace crankcase vent valve or coolant hoses

On BMW Z3 4-cylinder engines (M44) and 1999 and later 6-cylinder engines (M52 TU or M54), the intake manifold is configured as two sets of runners with variable lengths. Low end torque and high end power are improved by varying the intake runner length according to a map stored in the engine control module (ECM). The ECM, to determine the rpm at which to switch intake manifold configuration, uses engine vacuum, load and ambient temperature. The actuator used by the ECM to switch manifold configuration is a vacuum solenoid called the dual resonance intake system (DISA) valve. 

In 4-cylinder models, during low and mid-range engine operation, the DISA valve is kept closed, thus resulting in long intake runners. Once engine speed exceeds approximately 4,500 rpm, the ECM signals the valve to open, resulting in short intake runners and increased torque at the higher speeds.

On the 6-cylinder models, at low to mid-range engine speeds (up to about 3,750 rpm), engine torque is increased as the DISA valve closes a flap inside the manifold, effectively increasing the length of the intake runners.

From mid-range to high engine speeds (4,100 rpm and higher), DISA is de-energized. This opens the resonance flap inside the intake manifold and allows air to be drawn into cylinders through additional intake runners. This provides extra air for the power needed at higher rpms.

Another function of the 6-cylinder version of this design is that resonance waves inside the manifold pulse back and forth between opening and closing intake valves and help in cylinder filling.

If you have a hard-to-find vacuum leak, replace your intake manifold gaskets. If you find oil inside your intake manifold, replace the crankcase breather valve. Clean the inside of the intake manifold thoroughly but be careful not to get any debris inside the cylinder head during the procedure. Removing the intake manifold will also give you easy access to the engine starter, knock sensors or coolant pipes and hoses.

The 4-cylinder engine utilizes one gasket for all four intake runners.

Models with a 6-cylinder engine utilize a profile style intake manifold gasket. Over time, the rubber gasket hardens from heat or swells from oil contamination. 

To remove the intake manifold, you must first detach the fuel rail from the fuel injectors. To minimize fuel spillage, be sure to relieve fuel system pressure before beginning work. The best way to relieve system fuel pressure is to remove the fuel pump fuse and run the vehicle until the engine stalls. How to do this is described later in this procedure. Also, undo the gas tank cap to release vapor pressure in the tank.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Remove fuses #13 and #18 (check that this fuse applies to you vehicle).
Figure 1

Remove fuses #13 and #18 (check that this fuse applies to you vehicle). Use the fuse application chart located below your fuses to identify fuse number. Start and run engine until it stalls. Once engine stalls, attempt to start again, if it does not start, fuel system pressure has been relieved. Keep in mind; this does not remove all the fuel from the fuel lines, only the pressure. So you still need to be prepared to catch leaking fuel when fuel lines are disconnected. Disconnect negative (-) battery cable. See our tech article on Battery connection notes.

Models with 4-cylinder engine: 

Using a flathead screwdriver, loosen the secondary air pump inlet hose clamp.
Figure 2

Using a flathead screwdriver, loosen the secondary air pump inlet hose clamp. (green arrow)

Then remove the secondary air inlet hose from the air filter housing by pulling it straight off.
Figure 3

Then remove the secondary air inlet hose from the air filter housing by pulling it straight off. (green arrow) Then pull off the air pump and store in a safe place.

Next, you will unclip the three air filter housing retaining clips.
Figure 4

Next, you will unclip the three air filter housing retaining clips. (green arrows). One of the clips was hidden beneath the secondary air inlet hose. You will have to reach in behind air filter housing to access it.

Disconnect the intake air sensor electrical connector by pressing the wire release tab and pulling the connector straight off.
Figure 5

Disconnect the intake air sensor electrical connector by pressing the wire release tab and pulling the connector straight off.

Working at the air flow meter, twist electrical connector counterclockwise to disconnect.
Figure 6

Working at the air flow meter, twist electrical connector counterclockwise to disconnect. (green arrow). Then loosen the air flow meter hose clamp (yellow arrow). Once loose, remove the air filter housing from the engine compartment.

Then, loosen the secondary throttle body hose clamp at the rear air boot (green arrow).
Figure 7

Then, loosen the secondary throttle body hose clamp at the rear air boot (green arrow).

Once loose, pull the intermediate throttle out of the boot.
Figure 8

Once loose, pull the intermediate throttle out of the boot. You can leave the cables connected, just lay it aside.

Next, you will have to remove the throttle housing intake air duct.
Figure 9

Next, you will have to remove the throttle housing intake air duct. Start by removing the hose at the back (green arrow), pull the hose straight off the nipple on the intake duct. Then loosen the duct clamp (yellow arrow) and remove the duct from the throttle housing.

Next, you have to remove the vacuum hoses (green arrows) at the throttle housing.
Figure 10

Next, you have to remove the vacuum hoses (green arrows) at the throttle housing. Start by pulling off the smaller hose.

Then, pull the large hose off.
Figure 11

Then, pull the large hose off. If it will not come off easily, use a flathead screwdriver to lever it off. (green arrow) Be careful not to damage the hose while levering it off. Once the vacuum hoses are removed, disconnect the electrical connectors by pressing the wire release tab (yellow arrows) and pulling it straight off.

Working at the back of the upper intake manifold, use a flathead screwdriver and open the clamp for the brake booster vacuum hose.
Figure 12

Working at the back of the upper intake manifold, use a flathead screwdriver and open the clamp for the brake booster vacuum hose. (green arrow) Once the clamp is opened, remove the hose from the intake manifold. I have heard of people leaving this attached to the intake manifold, however doing so adds stress to the hose, fitting and sealing grommet in the brake booster and could cause a vacuum leak.

In order to access the rear intake manifold support bracket, I like to remove the wiring housing fasteners.
Figure 13

In order to access the rear intake manifold support bracket, I like to remove the wiring housing fasteners. Remove the two Phillips head screws (green arrows).

Then loosen the 11mm fastener (green arrow) at the rear support bracket.
Figure 14

Then loosen the 11mm fastener (green arrow) at the rear support bracket. Loosen it until there is about 5mm of clearance from the fastener washer to the bracket.

Then loosen the 11mm fastener at the front (green arrow) support bracket.
Figure 15

Then loosen the 11mm fastener at the front (green arrow) support bracket. Loosen it until there is about 5mm of clearance from the fastener washer to the bracket.

Next, remove the two nuts and one bolt (all 13mm) from the upper intake manifold.
Figure 16

Next, remove the two nuts and one bolt (all 13mm) from the upper intake manifold. (green arrows). Lift the upper intake up and off the engine, and place aside. Let it sit in the area of the air cleaner during the remainder of the repair. Now you can remove the alternator. You don't have to do this, but it makes getting to the electrical connections we have to disconnect later much easier. I suggest doing so, see our tech article on alternator replacing.

Now you will have to disconnect the fuel injector electrical connectors.
Figure 17

Now you will have to disconnect the fuel injector electrical connectors. There are four individual connectors you remove by pressing the wire retainer and pulling off.

It is almost impossible to fit a finger down next to the injector, what I suggest doing is use a flathead screwdriver to release the wire retainer, then pull up on the electrical connector.
Figure 18

It is almost impossible to fit a finger down next to the injector, what I suggest doing is use a flathead screwdriver to release the wire retainer, then pull up on the electrical connector. The fuel injectors do not have to be disconnected, however I find doing so makes it easier when accessing the fuel lines.

Next, you have to remove the fuel lines from the fuel rail.
Figure 19

Next, you have to remove the fuel lines from the fuel rail. Loosen the two 12mm nuts (green arrows). Once loose, pull the line out of the fuel rail. Place a rag under the lines before you pull them out to catch the fuel that will leak out. After removing the lines from the fuel rail, remove the two small O-rings for the ends. Store them in a safe place. You will have to reinstall them later, removing them helps to prevent losing them during the procedure.

Working at the rear of the intake manifold electrical junction, unlock and disconnect the main electrical connector (green arrow) by twisting it counterclockwise and pulling it off.
Figure 20

Working at the rear of the intake manifold electrical junction, unlock and disconnect the main electrical connector (green arrow) by twisting it counterclockwise and pulling it off.

Lift up the crankcase breather air plate and remove both coolant hoses.
Figure 21

Lift up the crankcase breather air plate and remove both coolant hoses. Loosen the hose clamps (green arrows) then pull the hoses straight off. Then disconnect the crankcase breather hose and lay the air plate aside.

Next, remove the 10mm fastener (yellow arrow) for the dipstick tube, Then remove the two 13mm intake manifold support fasteners.
Figure 22

Next, remove the 10mm fastener (yellow arrow) for the dipstick tube, Then remove the two 13mm intake manifold support fasteners. (green arrows). Detach the dipstick from the intake manifold and move it aside. Leave it installed in the oil pan.

Working at the bottom of the intake manifold support, remove the final two 13mm fasteners.
Figure 23

Working at the bottom of the intake manifold support, remove the final two 13mm fasteners. (green arrows)

Then remove the intake manifold support from the engine.
Figure 24

Then remove the intake manifold support from the engine.

Next, disconnect the camshaft and crankshaft position sensor electrical connectors.
Figure 25

Next, disconnect the camshaft and crankshaft position sensor electrical connectors. (green arrows) To disconnect them, press the wire release tab, then pull the connector straight out to remove.

Remove the five 11mm intake manifold nuts (green arrows).
Figure 26

Remove the five 11mm intake manifold nuts (green arrows).

Next, you have to remove the fuel hoses and detach the fuel lines from the mounting bracket.
Figure 27

Next, you have to remove the fuel hoses and detach the fuel lines from the mounting bracket. This will help later when you have to feed the lines through the intake runners when removing the manifold from the engine. Working below the starter (yellow arrow), remove the 10mm fuel line bracket nut. (green arrow) Then remove the bracket from the fuel lines.

Loosening the fuel line hose clamps (green arrows) requires a special socket.
Figure 28

Loosening the fuel line hose clamps (green arrows) requires a special socket. But here's the good news, you can get these off without it. When I didn't have the right socket, I would use my 6mm nut driver (yellow arrow) and tilt it just a bit so it would grab the hose clamp end. This would allow me to loosen both clamps. When reinstalling the hose, replace the factory clamp with a standard fuel injection style clamp.

The intake manifold is almost ready to be removed.
Figure 29

The intake manifold is almost ready to be removed. Start by reaching under the front of the manifold and disconnecting the coolant temp sensor (at front of cylinder head) and the oil pressure switch (back of oil filter stand). Next remove the three wires at the back of the starter, there are 8mm (red arrow), 10mm (green arrow) and a 13mm (yellow arrow) nuts that have to be removed. Once the nuts are removed, remove the wires from the back of the starter. Now you can start to pull the manifold off the cylinder head. Slide it off the studs, and check for any snagged wires of hoses.

When removing the intake manifold, feed both fuel lines (green arrow) through the intake runners.
Figure 30

When removing the intake manifold, feed both fuel lines (green arrow) through the intake runners. This is why we disconnected them from below, to allow enough movement to feed them through the runners.

Then feed the front coolant hose through the manifold runners.
Figure 31

Then feed the front coolant hose through the manifold runners. (green arrow) Be careful, if this hose is stressed too much, it may break the nipple off the coolant pipe on the block. If that happens and you need to replace the pipe, see our tech article on coolant pipe and hose replacing. Continue to remove the intake manifold while checking for snagged or connected items.

Once removed, seal intake ports to prevent debris from entering cylinder head.
Figure 32

Once removed, seal intake ports to prevent debris from entering cylinder head. You now have access to the knock sensors (green arrows), the coolant pipe and hoses (yellow arrows) and the starter motor (red arrow). Installation: Remove items you used to seal intake ports on cylinder head. Then install intake manifold to cylinder head and tighten fasteners in an alternating pattern. Reconnect sensor electrical connectors then reconnect fuel lines. Reinstall remaining items in reverse order of removal. Double check wiring harness routing and fuel line connections. Fill and bleed cooling system. Once complete, let engine idle for about 10 minutes, if you left something disconnected or an item is miss-routed, it is best to find out before driving.

Models with 6-cylinder engine:

Remove the air filter housing assembly.
Figure 33

Remove the air filter housing assembly. Remove the 10mm fastener (green arrow), then disconnect air flow meter electrical connector (yellow arrow). Now loosen the air flow meter clamp (red arrow) and lift the air filter housing out of the engine compartment.

Working at intake air duct, pull vacuum hose connector out of duct.
Figure 34

Working at intake air duct, pull vacuum hose connector out of duct.

Working at left front corner of cylinder head cover, disconnect crankcase vent hose by squeezing release tabs and pulling away from cylinder head cover.
Figure 35

Working at left front corner of cylinder head cover, disconnect crankcase vent hose by squeezing release tabs and pulling away from cylinder head cover.

Working near left shock tower, remove rubber weather strip from body by pulling off.
Figure 36

Working near left shock tower, remove rubber weather strip from body by pulling off. (yellow arrow)

Rotate panel clips 90 degrees counterclockwise to release.
Figure 37

Rotate panel clips 90 degrees counterclockwise to release. (green arrows)

Next, pull hoses up and out of trim panel.
Figure 38

Next, pull hoses up and out of trim panel. (green arrows) Be careful not to lose hose mounts, they have a tendency to fall off hoses.

Then pull trim panel (yellow arrow) up to remove, guiding it past hoses.
Figure 39

Then pull trim panel (yellow arrow) up to remove, guiding it past hoses.

Working at brake booster, remove brake booster vacuum hose (yellow arrow) by pulling straight out of brake booster.
Figure 40

Working at brake booster, remove brake booster vacuum hose (yellow arrow) by pulling straight out of brake booster. Remove throttle housing. See our tech article on throttle housing removing.

Working at top on intake manifold.
Figure 41

Working at top on intake manifold. Locate oxygen sensor connectors. (green arrows) Slide both connectors out of mounting bracket and lay oxygen sensor wiring harness aside.

Working at center of intake manifold, disconnect intake air temperature sensor electrical connector by releasing tab and pulling off.
Figure 42

Working at center of intake manifold, disconnect intake air temperature sensor electrical connector by releasing tab and pulling off. (yellow arrow)

Working at VANOS solenoid, disconnect VANOS solenoid electrical connector by releasing tab and pulling off.
Figure 43

Working at VANOS solenoid, disconnect VANOS solenoid electrical connector by releasing tab and pulling off. (yellow arrow)

Then release fuel injector harness strip from fuel injectors and remove.
Figure 44

Then release fuel injector harness strip from fuel injectors and remove. I find the easiest way to do this is to use a flathead screwdriver and gently pry up at each fuel injector. This will release the spring clips that hold electrical harness to fuel injectors.

Work your way down injectors while disconnecting injector harness.
Figure 45

Work your way down injectors while disconnecting injector harness. Lay fuel injector harness aside.

Working at right shock tower, open Battery positive (+) jump start connector.
Figure 46

Working at right shock tower, open Battery positive (+) jump start connector. Then using a 19mm wrench, remove nut from connection. Remove battery positive (+) cable from junction.

Working at top on intake manifold, unclip battery positive (+) cable from intake manifold.
Figure 47

Working at top on intake manifold, unclip battery positive (+) cable from intake manifold. (green arrow) Later in the procedure, when removing intake manifold from engine you will have to feed cable through intake runner.

Working at rear of intake manifold, disconnect fuel line by pressing release tab and pulling apart.
Figure 48

Working at rear of intake manifold, disconnect fuel line by pressing release tab and pulling apart. Have a rag handy to catch any dripping fuel. You will have to reach behind intake manifold, near firewall. (green arrow) You can see the line, but will have to do this part mostly by feeling.

Reach behind intake manifold, locate fuel line (green arrow).
Figure 49

Reach behind intake manifold, locate fuel line (green arrow). Push fuel line toward fuel rail (purple arrow) then press release tab (yellow arrow) and slide fuel line off connection. Have a rag handy to catch any dripping fuel.

Working below intake near throttle housing mounting surface (purple arrow), locate intake manifold mounting bracket.
Figure 50

Working below intake near throttle housing mounting surface (purple arrow), locate intake manifold mounting bracket. Then remove 16mm nut from mounting bracket. (green arrow)

Working at front of intake manifold, pull evaporative emission purge solenoid off mounting bracket.
Figure 51

Working at front of intake manifold, pull evaporative emission purge solenoid off mounting bracket. It is mounted in rubber bushing and pulls straight off bracket. (purple arrow) Disconnect electrical connector by squeezing release tab and pulling off.

Then disconnect canister connection hose by squeezing release tab and pulling off solenoid.
Figure 52

Then disconnect canister connection hose by squeezing release tab and pulling off solenoid. (green arrow)

Working at rear of intake manifold, disconnect solenoid electrical connector by squeezing release tab and pulling off.
Figure 53

Working at rear of intake manifold, disconnect solenoid electrical connector by squeezing release tab and pulling off. (green arrow) Then, reach between firewall and intake manifold, disconnect vacuum line at solenoid.

Remove nine 11mm intake manifold nuts.
Figure 54

Remove nine 11mm intake manifold nuts. (green arrows) Once fasteners have been removed, lift intake manifold up and off cylinder head. Cut wire ties securing wiring harness to intake manifold. Continue to lift intake manifold off cylinder head, disconnecting hoses or electrical connectors. Then remove intake manifold from engine. Once removed, seal intake ports to prevent debris from entering cylinder head.

Before installing, replace intake manifold gaskets.
Figure 55

Before installing, replace intake manifold gaskets. Remove by prying out with small flathead screwdriver. Install new gaskets by pressing in, check that all gaskets are properly seated before installing intake manifold. If you plan to replace your crankcase breather valve now is a good time. You have great access to it and can easily connect the hoses. See our tech article on crankcase breather valve replacing. Remove items you used to seal intake ports on cylinder head. Then install intake manifold to cylinder head and tighten fasteners in an alternating pattern. Reconnect knock sensor electrical connectors then reconnect fuel lines. Reinstall evaporative emission purge valve. Reconnect fuel injectors and intake air temperature sensor. Reinstall remaining items in reverse order of removal. Double check wiring harness routing and fuel line connections. Once complete, let engine idle for about 10 minutes, if you left something disconnected or an item is miss-routed, it is best to find out before driving.

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