Broken CIS airbox oil breather bung

Mitch1 · 12-08-2014, 06:05 AM

Just noticed yesterday that the breather hose running from oil tank filler neck to the right side CIS airbox was off. Inspected and found the air box bung for the hose was broken. Not sure how long it was like this. Maybe 100 miles or so. Was enough of the bung left to reinstall the hose. But not enough to give me confidence of a complete seal. The rest of the bung was in the engine tin in pieces. Not sure how it happened. Just brittle from heat? Seems like it should be an easy fix with a piece of similar plastic tubing inserted into hole in air box and glued? Anyone else have this issue?

Alan Lindquist · 12-08-2014, 11:50 AM

Mine was broken. The fix is pretty simple - I think you have the right idea. I used some hardware store parts and JB Weld to re-create the bung.

I also lost the bung connector at the top of the intake - the backside of the hat that joins the air metering plate and the throttle body. That one is serious - air is already metered at that point. Huge vacuum leak. Had to buy a new hat.

Heat and time - stuff gets old.

Mitch1 · 12-08-2014, 12:06 PM

Thanks Alan. Might cannibalize a generic pcv valve from flaps if I can find one with a fitting with correct OD.

Mitch1 · 12-08-2014, 12:56 PM

@ pmax, the hose is fine. It's the nipple from the airbox that's broken. I have it reconnected, just not real secure. I have a back dated CIS. The secondary air system, decel valve and aar valve have been removed. My tank breather hose now goes directly to air box.

Walt Fricke · 12-08-2014, 05:28 PM

Look on line at places which sell race parts. Summit, Jegs, Racer Wholesale, Pegasus, any large roundy round sales outfit. You will find fittings which will be suitable. The kind with one end a flat circle with an ID, the other threaded for a ways, and then straight with a bead on the end. With a thin nut to hold in place. Maybe with rubber washers for both sides, maybe not. These will most likely be in SAE/US sizes, but one will be suitable for your breather hose.

Just make the existing hole in the air box large enough so this will slip through, smooth off the broken outside, and assemble.

You should have a brass round strainer part which fits inside the now broken part. You can probably figure out how to reuse that - maybe just stuff it up hose? I think its purpose is to act as a flame stopper in case a backfire gets flames into that part of the airbox. Alternately, it serves to dampen pressure fluctuations, or make it a bit harder for liquid oil, however aerated, from getting into the air box. Whatever it is, Porsche thought it useful so I have been careful to keep it.

pmax · pmax's Garage

Quote:

Originally Posted by Mitch1

@ pmax, the hose is fine. It's the nipple from the airbox that's broken. I have it reconnected, just not real secure. I have a back dated CIS. The secondary air system, decel valve and aar valve have been removed. My tank breather hose now goes directly to air box.

OK, I was just wondering whether the damage in your airbox and the damage in Alan Lindquist's air boot could have been the result of a backfire.

In another thread, someone posted a pic of the boot torn where it connects to the air flow plate. I speculate that was the result of a backfire which blew the boot off at it's weakest spot. The boot is reinforced for a reason otherwise a simple rubber hose will do for channeling air from the meter to the throttle plate.