For B5.5 Passat TDI, see 1000q: clean passat intake. For other cars, refer to the FAQ.
The air intake manifold must be cleaned of carbon if there is excessive buildup. The BRM engine used in the 5th generation (2005.5-2006) use a different intake manifold, cylinder head, and exhaust gas recirculation cooler (EGR) than the previous generation cars. For the ALH engine, see 1000q: ALH engine intake removal as well. The main difference is the 2 piece split intake manifold with changeover valve. Some people prefer to buy a new intake manifold, some people prefer to clean their old intake manifold. To clean it, you could use a pressure washer and brush, chemical cleaning while off the engine, or ultrasonic cleaning. I do not recommend bead blasting since improper cleaning can leave tiny particles stuck in the carbon and cause engine damage. If you bead blast, make sure the intake manifold is completely clean on the inside, including the corners. There are chemical cleaners that work while the manifold is attached to the engine but I strongly do not recommend this. Dealers used to do this until engines were damaged. In a diesel, the valves are almost touching the pistons due to high compression and once you see how much crud is inside, you won't want that going through the engine. Wear clothes that you don't mind throwing away because they will be filthy after you clean the intake manifold. Wear gloves and eye protection, note all cautions in your factory service manual, etc..
Soaking the manifold in carb cleaner, biodiesel, or wood furniture stripper will clean the carbon effectively.
This is a also good time to clean the EGR cooler. This is the rounded rectangular silver object at the back of the engine that is connected to the EGR and the exhaust manifold. Removing the EGR cooler causes coolant to be lost so have replacement coolant handy. Warning: check the color of your coolant, do not mix green coolant with VW red/purple coolant, refer the article: 1000q: coolant flush for more details.
Most pictures from McBrew, original details and post is mirrored with permission from http://forums.tdiclub.com/showthread.php?t=141280. This article adds pictures, clarifies the instructions to the original post, and archives the pictures.
allen wrenches 5mm and 6mm
various pliers such as hose clamp pliers and needlenose
mirror to see the back of the engine
a brush, degreaser, and a power washer if you want to clean the intake
metric tool set
intake manifold gaskets
new intake manifold (optional)
0.5 L of G12 coolant
0.5L of distilled water
Summary of EGR removal: The EGR cooler is attached to a few small coolant hoses and the EGR's metal piping. You must first remove the piping, then the coolant hoses, and all bolts and brackets, and the EGR cooler will come off. This will let you remove the intake manifold.
EGR cooler removal:
Remove the 2 piece engine cover. It just pulls straight off.
Remove the air filter-intake accordion hose and the turbo intake hard pipe, and the crankase ventilation (CCV, similar to a PCV) hose. There are two bolts holding the turbo intake hard pipe. Also remove any vacuum lines. Mark both sides so you remember what goes where. I also suggest taping over the exposed piping with bright colored tape. I try to avoid using paper towels because they can get stuffed down into piping and forgotten.
There is a vacuum actuator for the intake swirl flaps (black plastic bulb) and a black bracket near the right side of it, you can remove it all in 1 piece so leave them attached. However, remove the 1 bolt that holds the bracket to the intake manifold (you will need to transfer the black bracket to the new EGR cooler).
Remove as many of the allen bolts on the EGR metal pipes as you can remove from the
top. Each metal pipe has 2 at each end, (8 x 6mm allen) total. Pipes
are pictured below. The location of the piping is also pictured later in
this article (4 pictures down).
Clamp off the two larger coolant hoses (see pic below) and pull them off of the cooler. The small hoses can be removed later when you have better access to them.
Remove the (3 x 5mm allen hex) bolts that hold the EGR cooler to the intake manifold, one on top and two on the
bottom, pictured below.
Now, there is one more bolt... the trickiest one! This on is on the left side. Here is the bolt hole indicated with an arrow, you can try using an extension here. Note: the bolt to the right of the arrow does NOT need to be removed.
Now, clamp off the smaller coolant hoses and remove them. You can clamp them back near the coolant glow plugs to keep the clamp out of your way Position the EGR cooler so that you can grab each hose with some pliers and twist them to loosen them. Once they twist easily, you should be able to pull them off by hand.
The EGR cooler should now be free. Pull out the EGR cooler.
EGR cooler installation:
Remove the black bracket from your old cooler and move it to the new one.
Connect the small coolant hoses first and the 4 small bolts and piping.
Note that there are 4 gaskets, 1 of which is metal. The metal gasket goes closest to the exhaust manifold on the only end that has studs instead of bolt. Plug the vacuum hose back into the actuator and re-connect the large coolant hoses.
The rest of installation is the reverse of removal. Make sure that you remove any tape or paper towels around the piping!
Also check your coolant level. This procedure causes the loss of a little bit of coolant so have G12 and distilled water available just in case to top it off. If you do not have enough G12 available, just top it off with distilled water and you can fix it later by removing some coolant out of the coolant reservoir with a turkey baster or vacuum and replacing it with G12.
Removing the intake manifold
At this point, all you need to do is remove 6 allen bolts holding the intake manifold to the engine head, the intake piping, and any vacuum lines. Here are pictures of the intake manifold removed from the head for reference. The allen bolt locations are circled in red. Note the block off plate on the manifold which disables the EGR. Again, this is a mk4 BEW engine intake manifold, yours may be slightly different.
Cleaning the intake manifold
The EGR naturally puts exhaust soot into the intake which must be cleaned out. Do NOT use a chemical dissolver or a vacuum cleaner to suck out the carbon while the intake manifold is still attached to the head. Hard pieces of carbon will fall into the engine and possibly damage the valves or turbo. The intake, EGR, and EGR cooler must be removed from the head for cleaning. Here is an example of how clogged the intake manifold can get. Note that this picture is from a non-pumpe duse car, your pumpe duse manifold is similar.
You have to look on the other side of the EGR to see the really bad clogging.
At this point, you could just buy a new intake manifold because they are not too expensive. Buying a new manifold will let you immediately change it and save car down time. I preferred to clean it instead. I used a pressure washer, soaked it in degreaser, and used the pressure washer again. A hose will NOT clean it, you need a pressure washer! It will cause a big sooty mess, so wear clothes you don't mind getting permanently stained. If you're using a pressure washer, make sure the water jet doesn't hit anybody because it could cause severe injury.
Installation is the reverse of removal. Use all new gaskets on the EGR, EGR cooler, and intake manifold.
Below is a video from a third party site showing another method to clean it
(older manifold shown). The buildup is mostly carbon and unburned fuel and
oil and can be burned away. Unlike the video, I strongly recommend that
all plastic components like the EGR valve to avoid damage to them. I'd
also wait a bit before dunking it into water. Obviously, burning it will
create a potentially serious fire hazard so make sure there is nothing flammable
nearby, take all precautions to avoid getting burned, let it cool before
handling, see the TOS Agreement for the full legal disclaimer. The fumes
are also bad for you to inhale and bad for the environment so make sure you take
all precautions to prevent inhaling the smoke.