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Under the Intake - What to Refresh?

28K views 169 replies 18 participants last post by  PabloCruise 
#1 · (Edited)
2002 (7/02) 325i - 160k miles. I got her @ ~108k miles. I do not know if O2 sensors have ever been replaced.

I recently pulled the P0491/P0492 (secondary air injection system insufficient flow) codes.

I plan to replace the pre-cat O2 sensors, and then pull the intake to replace vacuum line, check valve and control valve.

While I am in there, I plan to replace the CCV, and thought I might as well replace the oil filter housing gasket as well. Intake gasket will get replaced at same time.

Anything else to do while I am under there?

I thought I remembered reading about a vacuum line mod to decrease oil consumption. She is consuming oil some way/where.

Thanks all!
 
#2 · (Edited)
Starter is (more) accessible with the intake manifold off if you are into preventative maintenance.

Coolant hard pipes are good to do while there, they crumble at the ends and will start a slow leak, many replace them when under there even if you aren't actively leaking coolant.

Also change the vacuum caps on the back of the manifold... actually just replace every vacuum line you touch, they probably all need it.

Replace the dipstick tube O-ring, the one at the bottom that seals it to the oil pan. While you have the dipstick removed make sure to blow it out with air or brake clean, it can clog.

Speaking of vacuum caps, the vacuum line mod is called the "O2 Pilot Mod" and you can search for a thread here. Essentially you run a vacuum line from one of the unused capped vacuum ports on the back of the manifold to the port on the CCV diaphragm. I did this when I dove under the intake and believe it helped.
 
#4 ·
You're welcome.

For this job I highly recommend heading to Youtube and searching for the user 50sKid, he has a lot of fantastic E46 content and if you want his 2 part CCV replacement videos you will be able to follow him as he removes the intake manifold and touches a lot of the pieces you will need to interact with.
 
#12 ·
Take a look at your Vanos oil line (or buy it and the crush washers and return if not needed).
Probably only need the o ring for crankshaft sensor but definitely do OFHG
Disa o ring, throttle body gasket, and air distributor o rings. So cheap there is no reason not to.
Replace all vacuum hoses
 
#40 ·
I just did this on my 2004 with 195k. I did the full replace of everything under the IM.

- All coolant hoses (Hard, Soft, to/from the Heater cord)
- Camshaft Position sensors
- Temp Sensors (Coolant and oil)
- All VAC Hoses for EGR
- All VAC Hoses from IM to Jet pump to the Brake booster
- All VAC Hoses to the intake
- Intake boots
- Clean ICV and Throttle
- OFHG (Done earlier)
- Starter
- Gaskets
- ICV Grommet
- Intake Caps on back (my car does not have anything in the back so all ports are capped)
- Oil Dipstick ORing
- Fuel line regulator short small hose to F connector
- O-rings on Air Distribution
- O-rings on Injectors (Top/Bottom)
- Cleaned the IM with Purple SuperClean from Walmart in a large tubby (did really good job cleaning all the gunk/dirt on the IM)
- CLEANED all the stuff that was nasty/dirty under the IM/Car


Good luck....
 
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#45 ·
I have those. They are the wires that send the O2 Sensor data back to the DME. I do not like that they are in front of the hose. I have them neatly tucked behind the new hoses.
 

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#47 ·
Did it last week.

The first start was the only "oh please" let it start moment just because of everything that you touch under there.

Absolutely all is working fine. No issues.
 
#50 ·
STARTER...

Get the ETorx sockets...
  • I used a 3/8 in box wrench to get the bolt closer to the engine it came off fairly easily but I did have to add some leverage (pipe) over the wrench to get it loose
  • I used the eTorx to get the other bolt (removed the engine/body brace [big silver metal part under the tranny] to get access
  • Long set of extensions and swivel to get to the bolt, did not need the swivel but it made it easier

I hesitated to do it but after seeing the stuff you need to remove to get to it and after 195k it was a no brainer.

Good luck.
 
#51 ·
STARTER...

Get the ETorx sockets...
  • I used a 3/8 in box wrench to get the bolt closer to the engine it came off fairly easily but I did have to add some leverage (pipe) over the wrench to get it loose
  • I used the eTorx to get the other bolt (removed the engine/body brace [big silver metal part under the tranny] to get access
  • Long set of extensions and swivel to get to the bolt, did not need the swivel but it made it easier
I hesitated to do it but after seeing the stuff you need to remove to get to it and after 195k it was a no brainer.

Good luck.
I am trying to understand what you mean by "big silver part under tranny"?
 
#53 ·
Nice work, its pretty satifying once its all done. Btw, did you replace the vacuum lines on the other end at the SAP check valve & control solenoid behind the intake manifold? Those looked a little suspect as well, especially the "flared" one in the picture above.
 
#54 ·
QUOTE: I am trying to understand what you mean by "big silver part under tranny"?

Its the engine support brace. I always thought it was something not to be messed with but a while back someone said just remove it.. its not a big deal. You can drive the car but i dont without it for support.


It is #3 - reinforcement plate - in this diagram - RealOEM.com - Online BMW Parts Catalog

It has 8 16MM bolts once you remove it there is so much access to things that you can not believe.
 
#55 ·
QUOTE: I am trying to understand what you mean by "big silver part under tranny"?

Its the engine support brace. I always thought it was something not to be messed with but a while back someone said just remove it.. its not a big deal. You can drive the car but i dont without it for support.


It is #3 - reinforcement plate - in this diagram - RealOEM.com - Online BMW Parts Catalog

It has 8 16MM bolts once you remove it there is so much access to things that you can not believe.
Ah! The skid plate! I have dropped that many times.

I was figuring I had to pull the starter bolts from the top. There are 3, correct?

You used a closed end 3/8" wrench for the top bolt? I bet the angle was good for getting under the firewall.
 
#62 ·
I used closed-end, flexible-head ratcheting wrench for both bolts, but I also detached the transmission mount and lowered it. I tightened the bolts on assembly from the top, and torqued them from underneath with 4 feet of extensions (the last one had a wiggle head).

Just did this this past weekend.
 
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