This is for a 1987 560SL, located to the rear of the right valve cover. Its a black rubber tube about an inch wide coming out of the rear of the valve cover (see pics). From the valve cover, it goes to a tube built into the underside of the air filter housing.
It also has vacuum tubing coming out of it which leads to a small gray metal box (sensor? or relay?) which is mounted on a bracket, directly underneath the radiator's expansion tank.
I am thinking the rubber tube recirculates gases from the engine to the air filter housing for "re-use"?
I am also thinking the vacuum tubing leads to a sensor which measures the gases coming out of the engine and either turns on or off the car's air pump?
BTW, this vacuum tubing I found disconnected and it's been that way apparently for quite a while. The air pump has been dead since I bought it. I understand the pump's main purpose is to get air into the cats to heat them up faster during cold engine startup so they get to working status faster. Mainly an emissions control thing. On my list of things to fix but not pressing.
I am planning on replacing the rubber tube as it's developed a crack at the y-joint where the vacuum tubing connects to it just after it exits the rear of the valve cover.
I would just like to know or have my suspicions confirmed as to the purpose of the rubber tube AND the vacuum tubing which leads out of it.
Thanks in advance