It is recommended you do this every 40,000-50,000 miles. Installing an OCC (Oil Catch Can) can help prevent some of the carbon build-up, however cleaning is still necessary every ~60,000 miles.
COMING SOON ALONG WITH PHOTOS!
-B12 Chemtool Cleaner (2-3 cans)
-Carb/Brake Cleaner (3-5 cans)
-Some kind of tubing that will fit on the wet/dry vac and also into the intake valves
What to Replace:
-While you’re completing this DIY it is useful to change out your Intake Manifold Gaskets as well
Steps to Intake Valve Cleaning:
1) Disassemble the entire top end of the engine – start with the Cabin Air Filters and remove the housing as well
2) Remove Sway-Bar Mounts.
3) Your engine should now look like this (e60 535i). NOTE: Yours may look a little different if you have a 135/335i, but all n54’s are virtually the same.
4) Remove engine cover. It is fastened down by 4 bolts – 2 on the front of the block and 2 on the rear.
5) Disassemble the Air Intake. You MUST remove the entire airbox, however, the tubing itself is optional. I took off as much of the tubing as possible just to have additional room to work with – this could be very helpful for anyone with a 135/335i as there is less room in the engine bay to work with.
6) Remove this clip on the Intake Manifold
7) Remove the Charge Pipe (CP)
8) Pop the clip up on the Throttle Body to Charge Pipe connection. Mine hadn’t been touched in 6 years since the car was manufactured so it wouldn’t budge without removing the entire clip.
9) Use a Torx to unbolt the T40 as shown in this picture:
10) Loosen the clamp at the back of the Charge Pipe near the connection to the intercooler. NOTE: This clamp may be hidden unless you remove the air intake piping.
11) Before removing the CP fully – make sure this is unclipped. It is the same kind of clip from step #6. The clip is right near the CP to Throttle Body (TB) connection.
12) With the CP out the next step is to remove the Throttle Body. It is fastened on using 4 bolts. After the bolts are off be careful moving the Throttle Body until the 2 connections are unclamped from the TB.
13) Move the wires just above the intake manifold. This isn’t necessary but they could get pinched when removing the Intake Manifold so I like to get everything out of the way.
13-B) Remove the o2 sensor connectors as seen in this picture. I wish I knew how to get these out easily, but you really just need to keep patient and mess with them until they finally come undone.
14) Remove the Junction Box – this is a black box (that holds wires) that is connected to the Intake Manifold. There are a couple methods:
A) Remove the 3 bolts. These bolts are upside down and very hard to reach, but it can be done – it just takes some time and patience.
B) Remove the Clamps. My clamps were practically super-glued on so I didn’t have luck with this method, but many others have.
15) The intake manifold is fastened down with 6 nuts and 1 bolt. Undo all of these nuts and bolts.
16) Make sure nothing is constricting the intake manifold. It is ready to be pulled off now – make sure to remove it gently and carefully as to not pinch or pull any wires. NOTE: The intake piping at the back constricts removal but you can just push it down and back to get it out of the way. It is easiest if you get someone to help you keep the intake piping and any wires out of the way.
17) Before you start cleaning you NEED to verify which Intake Valves are opened or closed (either 3 or 2 valves will be closed). If you’re having trouble telling which are opened and closed try spraying some carb cleaner in there to see if it pools up.
18) Now the cleaning begins! There are multiple methods for cleaning the Intake Valves (including walnut blasting), but I opted for the Wet/Dry Vac method.
19) Spray the CLOSED intake valves with Chemtool cleaner and let it sit for 30-60 minutes (let it pool up in the valve)
20) Begin scrubbing with BRASS wires. Careful what you use because some metals will scratch the Intake Valves. Brass will not scratch or damage the valves at all.
21) Dilute the B12 Chemtool cleaner with water and then suck it out with the Wet-Dry Vacuum.
22) Spray the valves with the Carb Cleaner and use the wet-dry vac to suck it up as you do this. This method is exactly like what dentists do with the suction and water method.
23) Repeat step 19-22 as many times as necessary to get the valves to your desired clean.
24) So how do you open the Intake Valves you already cleaned and get the other 2 or 3 valves to close?
---With the manual transmission you can simply pull the e-brake and rock the car back and forth until you hear the valves click and change positions.
---For an automatic transmission you need to lift the car up and remove the radiator fan to get to the starter.
25) Put everything back together
26) Congrats!! You just finished a very complicated DIY project on an engine that is already tough to work on!