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Old 10-03-2012, 12:23 PM
Tiko530 Tiko530 is offline
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Location: NYC
Join Date: Sep 2012
Posts: 42
Mein Auto: 2003 530i
Originally Posted by pleiades View Post
What brand/model of pre-cat O2 sensors did you use?

Did you also replace the valve cover gasket and spark plug seals? These are "must replace" items because valve-cover removal will ruin them if they aren't already toast.

Is your car throwing any codes?


1. There's a flat gasket that fits between the vanos unit and cylinder head. It's pretty obvious and I think documented. Should be replaced when you do this job. Did you re-install the unit without a new gasket?

2. If you dropped a piston on a concrete floor, very possibly it has dented or warped and is out-of-round. Reading your description, it sounds like you didn't know about the piston with the loaded spring. It's not so hard that you can't hold the backplate down while removing or tightening the bolts.

3. When you say piston "caps" do you mean the small plastic caps with small O-rings that cover the piston bolts? If yes, I'm not clear on how one of those would be damaged.

There are various gotchas in this job but most have to do with trying to keep things well-aligned or torqued properly.

If your car isn't throwing any codes, you might still have vacuum leaks if you didn't replace the valve-cover gasket or plug seals.
I used Bosch O2 sensors, I also replaced the valve cover gasket and spark plug seals as well as the Vanos gasket.

Yea by piston caps i meant the two orange caps with the small O-rings. As far as I can remember the break was in the wall of the piston cap above where the O-ring sat so it didnt affect the o-ring at all.

I completely forgot to mention this earlier but another horrible mistake I made was overtorqueing one of the 6 mounting nuts when putting the Vanos back, as a result the 3rd engine head stud from the right snapped off with the nut while I was overtightening it. I assumed the new vanos gasket and the other 5 mounting nuts would be plenty to seal off the unit. Could the break in that one have compromised the seal? And if so is there any easy way to replace the broken engine head stud?

P.S. I wrote to Support@beisan and Rajaie was kind enough to contact me back very quickly and offer some possible solutions, I've responded to him with some clarifications, will post back with updates.
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