In this continuing article on detailing your engine compartment, I will go over the steps involved with removing and painting the intake manifold on the BMW E30 3 Series. We will be using my E30 325is as the car in question, however this article applies to all cars in general.
One thing that most BMW owners like to do is keep the engine compartment as clean and detailed as possible. In the case of E30 models, this can prove challenging. An easy step in making your engine shine is to paint the intake manifold. This gives a nice finishing touch to the engine compartment, and if you are like me, gives you a sense of pride when you open the hood.
The first step is to disconnect the battery of the car. We will be working around fuel injection components. There is a potential danger of sending spikes through the fuel injection system as well as raw fuel that could ignite from a random spark. Take caution anytime you are working around fuel.
In order to paint the manifold, I recommend removing it completely from the engine. This will ensure that you can paint every surface of the manifold without fear of overspray. While it is possible to paint the manifold installed, I found that to do it the right way, it must come off. , Now look at the driver’s side of the engine down by the air cleaner. You will see the Air Mass Sensor bolted to the air box. One the other end of the sensor, there is a hose clamp that holds the intake air boot to the sensor. Loosen the hose clamp and carefully pull the air boot off the sensor. (Note: you may find it easier to remove the boot by taking out the air box completely. Unplug the air sensor, and just remove the two 10mm nuts holding to the bracket and pull it out.) Now look at the top of the air boot. You will see two fittings looking from the top. On the left side is the fitting for the idle control valve. On the right side is the vacuum attachment for the power brakes. Start out on the right side and loosen the hose clamp holding the brake fitting into the intake air boot. Now, on the right side, disconnect the electrical connector from the idle control valve, and remove the rubber strap holding the valve to the bracket. Now look at the other vacuum hose off the valve. We will simultaneously have to pull the valve out of both hoses. You may need to use a bit of force, however it will just pop out. If it hasn’t already come off, remove the vacuum hose going from the control valve onto the throttle body fitting.
With all the fittings out of the intake air boot, now loosen the hose clamp holding the boot to the throttle body. Now take the boot off. Before you continue, inspect the intake air boot for cracks. This is a common location for vacuum leaks. If you see any cracks or holes in the boot, replace it with a new one. Pelican carries these boots for $12.67. Now, look down under the throttle body. You will notice a vacuum hose attached to the throttle body, this is part of the emission control system. You should be able to just pull this hose off.
Now remove the two coolant hoses for the throttle body. They are directly below where the idle control valve sits. Just loosen the hose clamps that hold them in place, and pull them off the throttle body. Be aware that you will most likely have some coolant spill out of the hoses. Now, remove the throttle and cruise control clips from the linkage and set them aside. Next, remove the mounting brackets fro the cables on the manifold. They are held in place by four 10mm bolts. Now disconnect the breather hose from the valve cover.
Now we must remove the throttle body from the manifold. This is done by removing the four 10mm nuts that hold it in place. Before you remove the throttle body, be sure to remove the electrical connector for the throttle switch. This is located directly below the throttle butterfly valve. Just press the metal clip down and pull the connector off. Now pull the throttle body off the intake manifold.
Now go over to the passenger side of the engine. We will need to remove the bracket that holds the intake manifold to the valve cover. Just remove the four 10mm bolts that hold it in place and set the bracket and bolts aside. Now remove the vacuum hose from the intake manifold going to the fuel pressure regulator and set it aside.
We now must remove the fuel rail in order to access the intake manifold nuts. The fuel rail is the conduit that transports the fuel from the tank to the injectors. The fuel rail is held in place by four 10mm bolts. Remove these bolts and loosen the hose clamps for the fuel lines on either end of the fuel rail. Now use light pressure and pull the fuel rail up. The injectors will pull out with the fuel rail.
Now come the hard part, actually removing the nuts. There are two nuts on each runner of the intake manifold. We must remove all of these nuts in order to pull the manifold off. It’s easiest to begin on the passenger side of the engine. Directly below the fuel rail location, you will see the upper nuts on each runner. Use an open-end wrench to remove all these nuts. Now, move over to the driver’s side. Can’t see the nuts, can you. This is the one aspect of BMWs that I truly hate more than anything else. Using a 10mm socket and a u-joint extension piece, work your way around the manifold from underneath and remove all the nuts. This may take some time, as they are really hard to get access to. With all the bolts removed, you can now simply slide the intake manifold off the studs. It’s a good idea at this point to stuff clean rags inside each of the intake ports to keep dirt and grime out.
Now we have to clean and prep the intake manifold. Chances are, there is a yellowish film all over the manifold. This is called Cosmoline. BMW used to ship the cars from Munich with a protective coating all over the cars. This is what the Cosmoline is for. Most dealers used a special solvent to remove all the Cosmoline. Usually they neglected to clean the engine off, leaving the yellowish film. In order to paint the manifold, we will need to clean it off. I’ve found that acetone works best to get all the Cosmoline off. Try to find an acetone that contains xylene, as this is an industrial cleaning agent and will work well to clean off the Cosmoline. Clean every inch of the manifold. We need to create a clean surface so the paint will adhere. Once clean, use some painter’s tape to cover the mating surfaces for the intake runners and also for the throttle body.
I like to use Wurth products for painting (available from Pelican) these paints are easily the best spray paint I have ever used. They flow even, don’t run, and dry fast. The high temp paints also leave a nice textured finish that really blends in with the intake manifold. In this case I am using Wurth’s high temp aluminum spray paint. This will give the manifold a natural metal look. Be sure to paint in a well-ventilated area. If you inhale too may paint fumes, you can give yourself brain damage. You might end up one of those drooling messes that huff paint for kicks.
Start out by spraying light even strokes across the manifold. This is the first coat, or “tack” coat. This will give the final coats a good surface to adhere to. Just use even pressure on the spray nozzle and spray a steady 8 to 10 inches away from the manifold. Now, go into the kitchen and open all the windows. Now pre-heat the oven to 400 degrees. Now place the manifold inside the oven at let it sit for 10 minutes. This will cure the first coat.
Pull the manifold out of the oven, CAUTION, the manifold will be hot. And begin to spray the second coat. Use a bit more paint when spraying the second coat; make sure to get all the small areas around the runners on top and on the bottom. Now put the manifold back in the oven and let it cure again for 15minutes. After 15 minutes pull the manifold out, and let it dry overnight. The next day, peel off the masking tape around the mating surfaces and clean off any over spray around the area.
Now, we are ready to re-install the manifold. Start out by placing new gaskets between the mating surfaces for the head and the intake manifold. Make sure the surfaces are clean before doing this, and do not use any sealer. Using the socket with a u-joint extension, install new self-locking nuts and tighten them down. You now will see the contrast of the freshly painted manifold to the rest of the engine.
We now need to re-install the fuel rail. Use new sealing rings on the ends of each injector and coat them with a little oil. This will help the installation. Just use a little amount, and then place all the injectors in the manifold. Now, push down on the fuel rail to seal the injectors in place. Re-install the four 10mm retaining bolts for the fuel rail and reconnect the fuel hoses on either side of the rail. Tighten the hose clamps to secure the fuel lines.
Now reinstall the securing bracket between the valve cover and the manifold using the four 10mm bolts, and reconnect the vacuum hose from the manifold to the fuel pressure regulator.
Move back over to the driver’s side and re-attach the bracket for the throttle cables using the four 10mm bolts. Now, clean off the mating surface for the throttle body and install a new throttle body gasket. Now slide the throttle body over the studs and tighten it down using four new 10mm self-locking nuts. Reconnect the throttle and cruise control cables to the throttle body and adjust them as needed.
Next, reconnect the small vacuum connection for the charcoal canister under the throttle body. Tighten the hose clamp that holds it in place. Re-install the electrical connector for the throttle switch at this time as well. Just push it on until it clicks and stops.
Now, take the coolant hoses for the throttle body and slide them onto the connectors. Tighten the hose clamps to secure them. You may need to add a little water to the coolant reservoir to account for any coolant that may have leaked out. Now, re-attach the intake air boot over the throttle body and tighten the hose clamp that holds it in place. Slide the vacuum connector for the brake booster into the boot at this time too.
Now, take the idle control valve and push it back into the intake boot at the same pushing the connector onto the throttle body. Slide the rubber retaining ring over the valve to hold it in place. Re-connect the electrical plug onto the end of the idle control valve. Now, put the end of the intake air boot over the air flow meter and secure it using the hose clamp. Re-connect the breather hose from the valve cover at this time as well.
Now take a look over the whole engine and check for anything you may have forgotten. Now re-connect the battery and start the car. If you get a high idle or surging, you have most likely forgotten a vacuum connection somewhere.
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