Shared Knowledge

"BMW Z3 - How to Replace the Shut-off (Purge) Valve"

15 October 2010

Summary: not a terrible do-it-yourself (DIY) but one torx screw is tough.

Background:

- BMW Z3, 2.8L, model year 1997.

- 49,000 miles.

- Check Engine light (CEL) lit.

- A scan of onboard computer diagnostic codes (DTC) revealed "Purge valve stuck open".

Shut-off (Purge) valve:

- BMW calls valve "shut-off" while everyone else calls it a "purge" valve.

- Valve part of charcoal canister that stores gasoline fumes.

- At car start up and at other times, onboard computer instructs purge valve to open allowing stored fumes to be drawn into intake manifold and be burnt.

- The charcoal canister is located on the driver's side, underneath the car, just to the rear of the rear jack point.

What is Needed:

- Floor jack or someway to lift rear of driver's side of car up off the ground.

- 10mm socket and ratchet or wrench.

- 15 torx wrench

- 3 Allen wrench.

- Work light.

- New purge valve. Do not know how car would run with purge valve removed so better remove and replace all at one time. In my case, local dealer did not have valve in stock so had to order. Valve can be found @ many Internet websites. Cost of new part @ dealer was $90.

How to Replace the Shut-off (Purge) Valve:

- Apply hand brake.

- Jack up car at driver's side rear jack point. Removing rear tire really will not help.

- Around rear jack point is a plastic cover held in place by 3 nuts. The bolts are part of the chassis. The nuts are 10mm. Remove all nuts and then remove plastic cover.

- Look up underneath the car and you will see the charcoal canister (canister) and inserted into it is the purge valve you can identify by the metal ring it has around the end of it. As with many car repairs, before I began part replacement, I looked at the orientation of the part in the canister. At this point not sure it made any difference but observed valve inserted into canister such that a flat spot on the valve that has writing on it is at the bottom almost perpendicular to the body of the canister.

- From looking at the new purge valve, it appears the valve just is pressed into the charcoal canister, so to remove the old one, I placed my hand on the end of it and gave a gentle twist. The end broke right away from the body (obviously the problem causing the open condition reported when the on-board computer scanned.)

- I then lifted the broken piece away from the canister and it dangled down on the electrical cable attached to it. Looking at the connector on the broken purge valve, to remove the chassis-end connector, I simply pressed down on the center of the metal clip holding the connectors together. I then unhooked the broken purge valve piece from the chassis cable.

 - At this point I knew a piece of the old purge valve was stuck into the canister and it was then I observed that directly above the valve was a screw holding a washer that overlapped the metal ring of the purge valve. Thus to remove the purge valve, I had to first remove the screw and associated washer.

- Of course, like many car repairs, there is very little room to work but using a 3 Allen wrench I slowly managed to loosen the screw until I could remove it by using my fingers. To loosen, you move the Allen wrench counterclockwise. (Note here, not sure how dealer or repair shop would handle this repair. They might actually remove canister!)

- Once the screw and associated washer had been removed, I notice that the screw actually has a 15 torx head on it.

- With the screw and washer removed, thought the broken valve would simple pull straight out of the canister but it did not. Used a long, flat blade screw driver to carefully pry up on the exposed valve metal ring. Tight, but eventually, broken valve came loose and I removed it from the canister body. I did note that the broken valve appeared to slightly rotate counterclockwise as it came out of the canister.

Note: not shown in picture above is a spring that can be seen inside the valve body. When I removed the broken valve from the canister, the spring when flying and I could not find it for the picture above.

- Mount new valve first and then connect control wiring or connect wiring and then install valve? As such a tight spot, decided to connect wiring first and get valve seated before attempting to get the torx head screw and washer back into place.

- With chassis connector fitted into connector on purge valve and spring click in place, lifted new valve up and into hole in canister. Guess from looking at new valve, thought all I had to do was push valve into hole but no matter how hard I pushed, valve would not stay in canister hole on its own and surely torx screw and washer could not be only thing holding valve into canister!

- Removed new valve and took closer look. No threads but on one side there was a raised bar and fingering the hole in the canister, I detected a sort of clockwise twist to the plastic. So inserted the new valve such that I would twist it clockwise and have the bottom be perpendicular to the canister base. Valve went in and was more-or-less tight but used a flat blade screwdriver to gentle tap metal ring of valve to get it to seat into the canister and it did.

- Now the hard part: get that torx screw and associated washer back in place. Using the fingers of my left hand, got screw and washer started into hole in canister, no problem and even managed to get screw to tighten up some with my fingers but still "long way" from having washer pressed against metal ring of new purge valve.

- Took a while but oscillating between using a 15 torx and 3 Allen, I was able to slowly get the torx screw to tighten up. Not fun as frustrating trying to get torx or Allen to seat into top of screw with so little space to work with.

- With new valve in place, replace cover and (3) 10mm nuts and lowered car back down onto floor. Started car and started and runs fine.

- Because I reset all stored diagnostic codes, have to wait till car has gone 80 miles or so before scanning on-board computer to see if "purge valve stuck open" error is completely gone.

Total time:

- Probably 2 hours.

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