Secondary Air System Check Valve Replacement doityourself

[shadowpuck]

For a few weeks, I've had a CEL and code for the secondary air system in the ZHP.
The code is P0411 - Secondary Air Injection System Incorrect Flow Detected.

I did some basic troubleshooting and discovered that the pump worked and was pushing air into the check valve attached to the exhaust side of the motor.
The valve is suspect, and can often fail. I could not find a real test sequence for the valve; earlier cars (pre 03-2003 production) use a vacuum actuated valve which can be tested quite easily. 03/2003- production cars get a newer redesigned valve that is air pressure actuated.

The secondary air system exists to help the vehicle meet strict emissions standards and to also assist the cats in coming up to temperature more quickly. The system injects fresh air into the exhaust during a cold start for a brief period of time (usually less than 2 minutes). The system should not affect driveability or performance at all; it is strictly an emissions device.

Since the check valve is one of the less expensive parts in the system (around $100) I decided to start by replacing it.

Parts (for 04/2003 production, please check for your application) and tools needed:
11-72-7-553-066 Check Valve
11-72-7-514-860 Gasket
11-72-1-742-644 Self Locking Nuts (2)

10mm socket
Extension
10mm Driver
Pliers

I found it was easiest to remove the washer fluid reservoir, and the secondary air pump so I could more easily access the check valve.
The picture below was after I had removed those components:

http://www.kcbmwclub.com/gallery/d/47404-2/IMG_5173.JPG

Drain the reservoir first!

The washer reservoir will have up to 3 electrical connections - one for the level sensor, one for the headlight washer pump, and one for the windshield washer pump.
Disconnect and remove those from the washer fluid reservoir.
With those connections removed, there's one 10mm bolt holding the reservoir in place.
Remove it and the whole reservoir should come out - it may take a bit of wrangling.

In the picture above, the check valve is the UFO looking silver thing in the center of the picture.

Next, I removed the secondary air pump; there's 3 10mm bolts holding it in place. Once those are removed, there's an electrical connection on the bottom.
Remove the two hoses connected to the pump (the hoses are press-fit with plastic collars - use a small screwdriver on the big hose on top of the pump).
The pump then will lift right out of its bracket.

Closeup of the valve and hose:

http://www.kcbmwclub.com/gallery/d/47408-2/IMG_5174.JPG

Secondary air pump removed, and the new check valve from BMW:

http://www.kcbmwclub.com/gallery/d/47411-2/IMG_5175.JPG

I found it easier to disconnect the hose from the check valve after it was removed from the car.
The valve is held onto the exhaust manifold by 2 10mm nuts.
I recommend having replacements handy since these are copper and will deform and/or "weld" themselves to the block.

This picture shows the valve removed along with its gasket:

http://www.kcbmwclub.com/gallery/d/47414-2/IMG_5176.JPG

http://www.kcbmwclub.com/gallery/d/47417-2/IMG_5177.JPG

http://www.kcbmwclub.com/gallery/d/47423-2/IMG_5179.JPG

Here's some comparison shots of the old versus new valve:

http://www.kcbmwclub.com/gallery/d/47426-2/IMG_5180.JPG
http://www.kcbmwclub.com/gallery/d/47429-2/IMG_5181.JPG
http://www.kcbmwclub.com/gallery/d/47432-2/IMG_5182.JPG

Assembly is, as they say, reverse of disassembly.
I reinstalled the check valve, then the secondary air pump, then the hoses, and then the washer reservoir.

http://www.kcbmwclub.com/gallery/d/47435-2/IMG_5184.JPG

It'll take a couple of drive cycles to know if this fixes the problem - I'll report back the results.

[mimalmo]

Nice writeup!

[Marcus-SanDiego]

Very nice, Shadow.

[kayger12]

Great job.

[danewilson77]

Way to go SP. Respect the work. Man...look at the gunk in the old one.

I cant believe the check valve is $100!!!! WTF!!

[shadowpuck]

oh, now, c'mon - any time you can walk out of the dealership for $100 you've won, right? :)

I'm more amazed at how little information there is on this system; there's really nothing out there.
I even contacted the BMW Club's tech advisor - he confirmed there's little out there in terms of troubleshooting information.

what's strange in this whole thing is in the process of making the system simpler, BMW actually eliminated one of the easiest ways to test the system. i'm still not sure if that's progress - they did eliminate one of the most common failure points, but now you're left without a real way to test the system.

at least the replacement isn't difficult. when i picked the part up at the dealer, they confirmed they replace this item quite often.

drove the car around some today after replacement, but, it wasn't cold enough today for the secondary air system to run.

[rpatrick21]

Very nice write up..

[Mtnman]

Excellent. I love seeing new things, especially when thay are easy fixes.

[rpatrick21]

I performed this process last Friday night (using this writeup as a guide) because I was getting the exact error code (P0411). Today is Monday and no CEL.. Fingers are crossed that it did the trick!

P.S. - I was able to remove the check valve by just unbolting the air pump and moving it to the side. It was a little tight working but I didnt have to do anything with the washerfluid reservoir. The whole process took about an hour..

Thanks again Shadowpuck!

[shadowpuck]

meant to post back that so far i've had no further issues since replacing the check valve.

i debated not removing the washer reservoir, so good to see its possible to replace this without needing to remove the reservoir.

[Hornung418]

Great thread! That little valve is muy caro!

[chris]

I would just add that it was a lot easier moving the washer reservoir, and rather than draining it I just plugged it with a reusable wine cork (don't tell the wife). I replaced the washer while I was there (11727514860).

You can test the check valve (one with no vacuum hose) by simple cupping two fingers and blowing in each end (or if you are so inclined just blow right into it). Only the correct end will open the check valve, my dead valve didn't.

[danewilson77]

I would just add that it was a lot easier moving the washer reservoir, and rather than draining it I just plugged it with a reusable wine cork (don't tell the wife). I replaced the washer while I was there (11727514860).

You can test the check valve (one with no vacuum hose) by simple cupping two fingers and blowing in each end (or if you are so inclined just blow right into it). Only the correct end will open the check valve, my dead valve didn't.

:like

HTC DNA, Williamsburg, VA

[NoVAphotog]

**pulls out defibrillator** *CLEAR!*

Can this whole system be removed from the car? Was at a meetup recently and someone who had an E46 pointed at it and said he removed his and the car ran fine, cleaned up the engine bay significantly.

[bshovers]

What's the easiest way to trouble shoot what's working and what's not working. I have this same problem.


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