How-To: Replace Your Secondary Air Pump (1996-up E36 6-cylinder cars)

[G. P. Burdell]

BMW E36 Secondary Air Pump and Non-Return Valve Replacement

Vehicles:
1996 and up U.S. E36 323i/328i/M3.

Symptoms:
1. A Check Engine light that returns the fault codes F5 and F6. These codes indicate that the secondary air flow system is too low for cylinders 1-3 and 4-6, respectively.

2. Before the Check Engine light comes on, you will likely notice a whining, scraping, screeching, whistling or groaning sound coming from the passenger side of the engine compartment. The noise begins immediately after a cold start and stops after a minute or two.

Problem:
The secondary air pump has failed due to moisture inside the pump.

Solution:
Replace both the secondary air pump and non-return valve.

Background on the Secondary Air Pump
The secondary air pump, located near the firewall on the passenger side of the engine compartment, draws air from the engine compartment and injects it into the exhaust manifolds to provide extra oxygen to the catalytic converter and reduce cold start emissions. A non-return valve mounted on the exhaust manifolds normally prevents exhaust gases from flowing back into the pump. When the non-return valve fails, moisture in the exhaust gases accumulates in the pump, causing it to eventually fail.

This pump normally sounds like a vacuum cleaner under the hood, and it only operates for the first couple of minutes after you start the car. It will not leave you stranded if it should fail. You can replace the parts at your leisure, unless you have an emissions inspection coming up.

Before replacing the pump and valve, you must first verify that (1) the pump is getting power, (2) the vacuum hose leading to the non-return valve (see pictures below) is intact and free of blockages, holes, and cracks, and (3) the vacuum switch under the intake manifold is working properly. Power problems, a leaky hose, or a faulty switch can also set off the Check Engine light, which means you may not need a new pump and valve after all. A BMW document with more troubleshooting information is available at: http://www.iluvmyrx7.com/temp/bmw/Se...m%20Faults.pdf

Thanks to rmn for posting the link. (Added 11/8/04)

DISCLAIMER: Conduct a thorough diagnosis and verify all part numbers before purchasing materials. Read the procedure carefully and have the proper tools available before beginning work. Reader assumes all liability and cost associated with the procedure described below. I am not responsible for any misdiagnosis, injury, or damage you may incur while performing this procedure. BMW list prices are current as of April 2003.

Parts Needed:
--One (1) secondary air pump (BMW part no. 11 72 1 744 490; list price $199.00)
--One (1) non-return valve (BMW part no. 11 72 1 744 255; list price $94.50)
--One (1) gasket for non-return valve (BMW part no. 11 72 7 505 259; list price $3.95)

Optional Parts:
--Three (3) air pump rubber mounts (BMW part no. 11 72 1 704 532; list price $16.20 each!) in case one or more of yours breaks during removal of the old air pump. They’re just little pieces of rubber with threaded studs embedded in them. Try to reuse your old ones, unless you have $48.60 to spend on three new ones. I broke one of my mounts, but I had one left over from another project.
--Any hoses that are cracked.
--A nylon zip-tie.

See Figures A and B to identify components and for additional part numbers.

Tools Needed:
Ratchet with extensions
Adjustable wrench
10mm socket
Flathead screwdriver
Wire cutters or scissors (optional)
Fault code reset tool (if a Check Engine code was the cause of all of this)

Tightening Torques:
I don’t know if there are exact torque specs for any of the fasteners involved. Hand-tightening ought to do the trick.

Procedure:
1. Unclip the air intake snorkel from the pump. You may find water droplets inside the pump and the snorkel. Sling the water out of the snorkel and set it aside to dry.

2. Remove the non-return valve from the exhaust header by removing the two 10mm nuts on the flange at the bottom of the valve. Don’t be surprised if the nut on the left side takes the stud with it. You can just screw the entire thing in when you put things back together.

3. Unscrew the clamps on the hose connecting the air pump to the non-return valve and pull both ends of the hose off. If there’s water in the hose, sling it out of there and set it aside to dry. Pull the vacuum tube off the old valve and remove the old gasket if it’s still stuck to the exhaust manifold. Examine the vacuum tube, hose, and snorkel for leaks and replace if needed.

4. Remove the three 10mm bolts holding down the bracket in which the air pump sits. This will allow you to tilt the entire assembly for access to the air pump mounting nuts. You may also find it useful to unclip the diagnostic port from the strut tower and cut the zip-tie that holds various wires to the air pump mounting bracket for greater flexibility. See Figure C.

5. Remove the three 10mm nuts on the underside of the air pump mounting bracket. The rubber mounts have a solid hexagonal piece molded into each end so you can use your adjustable wrench to prevent the rubber mounts from twisting as you turn the nuts. Note that the stud molded into the rubber mount is not continuous all the way through, so you’ll have to grab the mount at the end closest to the nut to keep the mount from twisting. Excessive twisting will cause the mounts to break. Note what I said before about the exorbitant expense of these little pieces. If you’ve already shelled out the money for the three new mounts, just cut the old ones in half.

6. Lift the old pump out of the mounting bracket and unclip the electrical connector at the bottom of the pump. If you snipped the old rubber mounts in half, remove the nut and the bottom half of the mount from the mounting bracket.

7. Install the old rubber mounts (or the new ones) to the threaded holes on the underside of the new pump. See Figure D. Mount the new pump on the air pump mounting bracket. Again, use your adjustable wrench to prevent the mounts from twisting while you turn the nuts.

8. Reconnect the electrical connector to the bottom of the new pump, then bolt the air pump mounting bracket to the body of the car.

9. The new non-return valve includes a black plastic cap. Snap it onto the top of the new valve, then install the new valve and gasket to the exhaust manifold.

10. Remove the caps from the new air pump and replace all hose connections. Don’t forget the little vacuum line on the non-return valve. Install a new zip-tie if you cut the old one. Place the diagnostic port back on its bracket.

11. Clear the engine fault code, if there was one.

12. You’re done!

[G. P. Burdell]

Figure A: Passenger side of the engine compartment.

1. Secondary air pump
2. Non-return valve
3. Diagnostic port
4. Air hose from pump to non-return valve
5. Air pump intake snorkel
6. Non-return valve vacuum line

[G. P. Burdell]

Figure B: ETK screenshot showing individual parts.

[G. P. Burdell]

Figure C: 10mm bolts connecting air pump mounting bracket to body of car.

[G. P. Burdell]

Figure D: Attaching rubber mounts to threaded holes in underside of pump.

[OldSpice]

Hi, I've searched in the 5 series forum and couldn't find any information about this, so I was wondering if anyone had any idea where I could find the Secondary Air Pump Relay at? I've just replaced the secondary air pump on a 2000 540i and the CEL still comes on. So I hooked the scanner up and it states that the relay is at fault. The only problem now is, I cannot find the relay? I've called the dealer and they don't have such a relay listed in their system. Any help is appreciated. Thanks!

[10kken]

GP, this is a great write up, done as only an engineer could do! I think I may also have to do this, and this will be a big help. Although, I'm wincing at the prices listed for the parts.

Regarding the cost of the parts, did you happen to compare the prices from say, Circle BMW vs United BMW w/BMWCCA discount?

And hpw long would you say it took to do this? It looks like it would have been pretty quick since the parts don't appear to be under a lot of other parts.

[G. P. Burdell]

Thanks for the compliment. The prices for the pump and valve (and, heaven help you, those three rubber mounts!) are pretty high, but if you had to listen to the dying goose that was my old pump, you'd have changed it out too.

I did not compare the prices. I buy the majority of my parts through the guys at the local dealership, where I get 15% off list and I usually don't have to wait - or pay for shipping.

The entire thing took me a couple of hours, but I stopped to clean the pollen-covered engine bay, sneeze, take pictures, and scribble notes. As long as you don't dawdle like I did, the job should take no more than 1.5 hours with the right tools. Loosening the nuts on the bottom of the mounting bracket while holding the rubber mounts stationary on the other side is the tricky part; that was the most time-consuming step for me.

[thurst0509]

I just wanted to bump this thread back up and give a big THANK YOU to G. P. Burdell for providing this writeup!

I had been needing to do this for a while and finally got around to ordering the parts last week. Using this writeup, installation of the new pump and valve was easy as cake and took me only 45 minutes! The tips about how to work with the (apparently fragile) rubber mounts were great, and I managed to do it without breaking any.

Thanks again G. P., and thanks for all the great technical help you provide to this forum on a daily basis!

[PENER]

Originally Posted by OldSpice

Hi, I've searched in the 5 series forum and couldn't find any information about this, so I was wondering if anyone had any idea where I could find the Secondary Air Pump Relay at? I've just replaced the secondary air pump on a 2000 540i and the CEL still comes on. So I hooked the scanner up and it states that the relay is at fault. The only problem now is, I cannot find the relay? I've called the dealer and they don't have such a relay listed in their system. Any help is appreciated. Thanks!

Why did you have to replace your sec-air pump?

[fgraziano]

Could this system be removed? would you just need a blockoff plate to cover the port in teh header? does this only effect cold starts or is it a constant thing? has anyone removed this system ie for a track car (weight reduction)?

[T///Mac]

On figure A, item #2 (non-return valve) does the black plastic cap on this part come off? I just had my car serviced and I knew I had a black cap like that when it went in, now it's just metal. I couldn't figure out what was different until I saw this pic. I just wanna know if the mechanic forgot to put the cap back on or something.

[G. P. Burdell]

Yes, the black plastic cap comes off.

[T///Mac]

Thanks. Does the cap have any effect on the function? For some reason I'm now getting P1421 and P1423 codes.

[roberam]

What type of service did you done?
The black cap is for cosmetics only, I don't think it has any function

[328 is man]

could this cause a decrease in performance?

[G. P. Burdell]

Could what cause a decrease in performance?

[328 is man]

this pump goin bad

[vinay]

Can I republish this DIY on http://www.bimmerdiy.com ?

[G. P. Burdell]

Originally Posted by vinay

Can I republish this DIY on http://www.bimmerdiy.com ?

You can post a link to this thread on your site.

[supark]

wow - old post - though I guess it's nice to have a writeup on it - better to just remove it entirely. Mine doesn't have it (probably cause it went out and it didn't make sense to replace it. All it does is inject air into the exhaust gases I believe to thin it out when you first start the car up so it'll pass stringent US emissions tests. It doesn't really reduce the amount of crap you're putting in the air - it just mixes more air in with the contaminants.

[G. P. Burdell]

Originally Posted by supark

Mine doesn't have it (probably cause it went out and it didn't make sense to replace it.

Your '93 325is didn't come with one. The pump is part of the OBDII emissions control equipment package.

[bkloster]

G.P,
Thanks for posting write-ups like these on this board. I had a few questions for your expertise however. I am a new owner of a 1997 BMW 328i in near perfect condition. The check engine light came on and I took it to the local BMW dealer so they could charge me $101 to assess the problem is the secondary air pump and arrestor valve (no-return valve). I do not really have any car specific tools, but I have a large variety of general ratchets and home tools. I have never really attempted to fix my own cars to this degree, but I consider myself pretty handy and able to fix general mechanical problems fairly well.

Do you reccomend me even attempting this process? Should I invest in the diagnostic tool used to check the computer and why the check engine lights are on? (not sure the technical name for it)

Any advice/input is greatly appreciated!

thanks

[thurst0509]

bkloster,

I would certainly recommend investing in the diagnostic tool. The $101 you just paid at the dealer would almost pay for the entire tool itself ($138 at www.bimmerzone.com). The tool comes with a booklet explaining each error code, and this forum is a great resource for actually figuring out what each reading means (and how to take care of it). Mine has certainly paid for itself several times by now, and local guys sometimes even bring me beer in exchange for using it!

Regarding this procedure, it was extremely easy. As long as you have the basic tools listed in the procedure I would say go for it. I don't have much experience working on cars either, but I enjoy learning and doing things myself as much as possible. With very very basic mechanical knowledge, you should be fine following this procedure!

[G. P. Burdell]

Like SpoogE said, this is a very easy DIY since the parts are easily accessed and you only need basic tools.

As the owner of the car, you should be the one to decide whether to do the repair yourself or take it to a shop. If you feel comfortable doing the work after reading this thread, then dive right in and save yourself some money. If you don't feel comfortable doing the work yourself, take it to a local independent BMW mechanic (whose rates are usually lower than the dealer's) and have him do it.