rysagreg

I'm looking for some help here! I have a 2002 996, cab, tip, C4, 105,000 miles and recently I keep blowing out cam plugs. Then oil drips down on the exhaust and smokes. Here is what I do know: I have not replaced the valve cover gaskets (I heard that gasket sealer can block the passage ways and cause excessive pressure in the crank case and pop out cam plugs), I did replace the AOS about 20,000 miles ago. I recently replaced the breather elbow. No engine lights on. I replaced the cam plugs and drove around town for several days and then it pops out. Replaced it and it lasted several weeks, then out of know where, pops out. I have had 3 pop out and cannot figure out why.

I might be wrong, but I have heard the AOS can cause this. However, my thinking would be a failed AOS causes vacuum, not pressure in the crank case. Again, I might be totally wrong on this.

Any help would be appreciated!
Thanks again everyone, Greg

rysagreg

Additional information: It's the larger brown cam plug, not smaller green plugs. Initially the driver side blew out. Since then, three times and all three times, the passenger side.

Ahsai

Can you use a manometer to check the crankcase pressure? I really hope you don't have positive pressure in your crankcase.

There are no oil passages around the big brown plug so the only explanation is positive crankcase pressure.

rysagreg

Ahsai, thanks for responding. What would cause positive crankcase pressure?

Porschetech3

A little bit too much blow-by will cause the big brown cam plugs to pop out. Do a compression test and leak down test to determine if the ring seal is a bit low.

The TRG Race Teams had a stable of cars running in the GrandAm circuit that used to come to our shop the week before the Porsche 250 to prep their cars for the race at Barbers Motorsports. They had the same problem with the big brown cam plugs popping out. They had a good maintenance program and would refresh their engines after X amount of hours in their engine shop, or sometimes if they didn't have an engine ready they would just buy one from our parts department and swap it.They had a stable of about 10 cars in various classes and would use our shop after hours and work all night prepping, ( sometimes sleeping the the 18 wheelers during the daytime).

To keep the big brown cam plugs from blowing out, even on new engines , they had an aluminum plate made to bolt across the plug to retain it. Also used a bit of glue to help hold it in.

Because the brown plug is a lot bigger diameter, it is much easier for a small amount of pressure to blow it out as compared to the green ones.