G2: DIY: Miscellaneous: Intake Manifold Removal and EGR Cleaning
This guide explains how to remove and disassemble the intake manifold to clean out all of the EGR (Exhaust Gas Recirculation) passages. The EGR system recirculates exhaust gases back into the intake manifold under certain conditions, to reduce emissions of NOx (oxides of nitrogen, primarily nitric acid and nitrogen dioxide) by lowering combustion chamber temperatures. The EGR system on Legends is known to become clogged with carbon deposits formed by the mixture of exhaust gases from the EGR and oil from the PCV system. When the EGR becomes clogged, is it not enough to simply remove the EGR pipe and clean it, the entire intake manifold must also be removed to clear out the passages inside. Note: Cleaning the EGR system will not clear CEL code 12. Code 12 is set when the ECU detects there's a problem with the EGR valve opening and closing. (see G2: FAQ: Error Codes: CEL 12). A clean EGR system is essential to the operation of your engine. A clogged EGR system can result in head gasket failures (read more on that here).
1. Removing The Intake Manifold
A. Drain Coolant
Raise the car and put it up on jackstands. Remove the splash shield from underneath the radiator, this shield is held on by more than 10 bolts (M6x1.0). Remove the radiator cap. Loosen the drain plug on the bottom drivers side of the radiator with a drain pan underneath it. Once the coolant stops flowing from the drain, tighten the drain plug (loosely, just until snug, it's only made of plastic). The coolant does not need to be emptied completely for this procedure, so don't worry about getting out every last drop. Remove the upper radiator hose. Remove the coolant hoses from the IACV (Idle Air Control Valve) and FIV (Fast Idle Valve), two hoses each. Alternatively you may unbolt the IAC and FIV from the intake manifold and leave the coolant hoses attached (this will not leak any coolant), don't forget to replace the o-rings (two on the FIV, one on the IACV) if you use this method.
B. Strut Bar
C. Fuel Rail Covers
Remove the fuel rail covers (two 10mm head M6x1.0 acorn nuts for each cover).
D. Fuel Line
Wrap a rag or towel around the fuel filter. Loosen the "service bolt" on the fuel filter slowly until fuel starts leaking out. Allow the fuel to leak out and absorb it with the towel. Continue to loosen the service bolt until the fuel stops leaking and the pressure has been relieved. Do not loosen the service bolt too quickly or fuel will spray out.
Remove the main fuel feed hose from the fuel filter and passenger side fuel rail.
E. Throttle Body
The throttle body does not need to come off with the manifold, so we'll be leaving in place for this procedure. This way you don't have to disconnect the throttle and cruise control cables. Loosen the clamp around the air intake tube and slide the tube off of the throttle body. Remove the two bolts and two nuts that hold the throttle body to the manifold. Push the air intake tube out of the way and slide the throttle body off the studs, then set it aside but make sure not to bend or kink the throttle cables.
F. Electrical Connectors
Disconnect all the electrical connectors from the IAC, Coolant Temperature Sensor, Coolant Temperature Sending Unit, Intake Air Temperature Sensor, and all six fuel injectors. Try not to twist the fuel injectors as you remove the electrical connectors, that could damage or tear the o-rings and cause a fuel leakage. Unbolt the ground from the passenger side fuel rail.
G. Vacuum Lines
Disconnect (and label!) all the vacuum lines from the Fuel Pressure Regulator, PAIR valve (Type I engines only, Type II does not have a PAIR system), and both IAB diaphragms (aka VIS). Also disconnect the three vacuum lines from the upper rear passenger side corner of the intake manifold. These three can be installed on any of the three ports there, so don't worry about labeling them individually. Disconnect the PCV hose from the intake manifold behind the throttle body opening. Unbolt the FIV air pipe "elbow" from the back of the intake manifold, also disconnect the hose from the metal pipe that runs along the top of the passenger side valve cover. Disconnect the brake booster vacuum hose from the rear of the intake manifold.
H. PAIR and EGR Pipes
Unbolt the PAIR pipe between the PAIR valve and drivers side exhaust manifold (Type I engines only, Type II does not have a PAIR system). It's not necessary to completely remove the PAIR pipe, you can just unbolt it from the intake manifold and leave it connected to the exhaust manifold. Remove the EGR pipe from between the intake manifold and the passenger side cylinder head. Don't forget this step! If you try to yank the intake manifold off without this pipe disconnected, it could very easily break.
Unbolt the water passage from the block. There are two bolts on each end (10mm head M6x1.0). This water passage will come out as a unit with the intake manifold, so don't try to pry it out after removing its 4 bolts.
Unbolt the intake manifold from the cylinder heads. There are 4 bolts and 4 nuts (12mm head M8x1.25). Lift the manifold up slowly, always checking for any remaining hoses or electrical connectors that are still connected. There is one pipe underneath the manifold that may appear to still be connected, but it is only pressed in with an o-ring. Simply pull up to break it free.
2. Disassembling And Cleaning The Intake Manifold
Now that the intake manifold has been removed from the engine, it can be disassembled to reach the internal EGR passages.
Turn the manifold upside-down. There are nine bolts and two nuts holding together the entire manifold assembly. They are all 12mm head, M8x1.25. Many of them are different lengths, so keep track of where each bolt was removed for re-assembly. Each bolt length is also labeled in this diagram for reference. Remove both nuts and all of the bolts pictured here. If you only want to remove the lower section to clean the EGR passage and leave the rest of the manifold assembled, leave the single 45mm bolt in place.
To separate the lower section, pry with screwdriver as shown here.
Remove the three bolts holding this plate on the rear of the lower intake manifold section. They are all 10mm head, 20mm length, M6x1.0.
If you are only removing the lower section, stop here and continue at #B. Cleaning.
To separate the water passage and throttle body neck from the middle section, pry with a screwdriver as shown here. The water passage itself is held in place only by the throttle body neck and is not bolted to anything. The two pieces will come off together and will need to be re-installed the same way.
To separate the middle section from the upper section, pry with a screwdriver as shown here.
The main purpose of this DIY is cleaning out the carbon deposits from the rear of lower intake manifold section and the EGR pipe. Start by scraping off as much is you can with a screwdriver. You will then need to use a solvent of some kind to clean up whatever is remaining. There are a number of cleaners I have tested to find what works. Be careful what you use to clean the middle section of the manifold, it has a sealant around the edges of the VIS flaps and degreasers can dissolve or peel this right off. If you are going to soak the middle section, remove the flaps first and clean them by hand.
(in approximate order of strength)
- MEK (Methyl Ethyl Ketone). This is available at many hardware stores, usually around the paint thinners, though it is much stronger than acetone or any other paint thinner (Xylene/Xylol, Toluene, etc). It is safe on aluminum but not safe on plastics or rubbers. If you can remove all parts from the intake manifold that are not aluminum (A Type II badge is not metal, and would probably be dissolved into nothing if immersed in MEK!), you can soak the entire thing in a metal bin filled with MEK. A few minutes of soaking should do most of the cleaning. Take it out and rinse immediately with water. If you do not rinse quickly enough, the MEK will evaporate and leave behind the carbon it had dissolved. Repeat this process if needed until the manifold is clean. You can also use a wire brush to speed up the process on thicker deposits.
- SuperClean. This is one of my favorites. You can buy it in spray bottles or in gallon jugs. SuperClean contains sodium hydroxide (lye), which is very corrosive, will burn your skin, and eat away at aluminum. There is only a very small percentage of it in SuperClean, but you still need to wear rubber gloves and eye protection. Do not soak any aluminum parts in SuperClean, instead spray it on the part you are cleaning and use a brush to scrape away the carbon. Rinse it off thoroughly with water and don't let it sit for more than a few minutes or it will start to eat away at the aluminum.
- Carb Cleaner from any auto parts store. Using this will require less scraping/brushing, as you will just spray it on and watch the high-pressure solvent (usually Xylene or MEK) wash away the carbon. But it will end up being very expensive since you will need a lot of cans to clean an entire intake manifold. Brake cleaner is a similar product, which normally contains Toluene. It evaporates faster and leaves no residue behind, but is not as strong as Carb cleaners.
- EasyOff Oven Cleaner. Like SuperClean (above), this product contains sodium hydroxide. It comes in an aerosol spray and has very dangerous fumes. One benefit that EasyOff has over SuperClean is that it sprays in a thick foam, so it stays where you spray it instead of running. There are other EasyOff brand cleaners that come in spray bottles and some with less hazardous fumes, but they are not nearly as strong as the original. It is a great cleaner but not well-suited to cleaning up the thick carbon deposits that will be found inside an intake manifold.
- Greased Lightning. Works similarly to SuperClean, but not quite as strong. Also contains lye.
- X-It Carbon Cleaner from AircraftSpruce.com. This is not particularly strong. It should work well enough if you buy enough to soak the parts in, although it costs about $25/gallon. It will take a while to soak through the tough buildup, but it is safe on all metal surfaces.
- General purpose degreasers such as Purple Power, Simple Green, Gunk, etc. These will work fine to remove grease and oil but will hardly make a dent in the majority of the carbon. After cleaning the manifold with any of the above chemicals, you may want to give it another quick cleaning with one of these to make sure any remaining residue has been washed away.
Installation is the reverse of removal. Remember to replace all o-rings and gaskets.
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