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      01-20-2013, 08:10 PM   #11

Drives: 03 Turbo Cobra, 2011 335xi
Join Date: Jun 2010
Location: Wallingford CT

iTrader: (3)

Originally Posted by simon View Post
Sorry if I'm being unclear. Here's what I did:

1. Broke crank case vent hose
2. Broke entire valve cover (it came off in pieces, wtf)
3. Installed new valve cover and gaskets
4. Removed IM and replaced crank cent hose
5. Reinstalled IM, and all other parts
6. Start car and hear ear piercing hissing and violent idle surge

I think idle surge may be cause by crank vent hose and hissing by improper IM installation / bad gasket. Seem reasonable?

Thanks again.


The surging idle is because of a vacuum leak, the vacuum leak is the hissing you are hearing.

Many things can cause that. If the valve cover was not installed correctly, if the valve cover gasket came out of place somewhere, the crank case vent hose not clipped on properly, oil cap not latched on properly, intake air tube not connected to the throttle valve properly etc.

Did you put all the bolts into the valve cover in the correct spots? There are 4 different style bolts on that cover. Did the valve cover gasket fall out of the back of the cover near the firewall? This sometimes can happen.

Easiest way to find the leak is to smoke test it, but I doubt you will have a smoke machine.

I highly highly doubt its a bad intake manifold gasket. They are reuseable and never really go bad.

Something went wrong with the install. There is a leak for sure somewhere and that is causing your hissing and surging idle. You need to figure out where that leak is and problem solved. I hope you didnt crack that new valve cover installing it.