just Got the car, I didnt notice this before I bought it. Is this a problem? I haven't had it inspected yet.

Thanks

What car??? Some don't have them. If disconnected and
you have to pass emissions test, it has to be in working
order and connected.

Gary

The car is a 1988 420 SEL

smog pump
 

I have the same car and my smog pump went bad at 77,000 miles. The symptom is a shriek on cold starts that may last 30 to 45 seconds. There are a number of good posts on this board -- just search under "smog pump".

The prior owner probably disconnected it to stop the shriek. While the car will appear to run fine without it, I understand that in time the catalytic convertor can be damaged -- and as the convertor is a couple of thousand $$, I am going ahead and fixing mine.

A new pump is $600, but a rebuilt pump can be obtained for under $300 from BenzBin (http://www.benzbin.com -- ask for Paul) -- you will need to return your old pump for credit (you are charged $500 and get $200 back when the old pump is returned). I understand that the labor is minimal -- just disconnect the belt, unplug the hose to the pump and there are two bolts to remove and install it.

Smog pump pointer
 

Dave,

I don't know if the 420SEL is that much different from a M103 in a 1991 300TE, but there was a vacuum operated valve in the air pump discharge line that died on mine and, I believe, hastened the demise of my first rebuilt air pump. The warranty on the second rebuild, this time from thebenzbin, specifically mentioned the warranty would not be valid if this valve were defective. It was about $35 and easy to replace.

Again, your model may not have it, but check it out.

smog pump valve
 

Actually the mechanic has determined that the same thing happened to mine! Good idea to check the valve.

some how I was able to pass the inspection with the pump disconnected. The car seems to run fine. Should I get it repaired?

smog pump
 

Since the smog pump runs when the convertor is cold, you may be able to pass the inspection if the engine is warmed up and the inspector doesn't notice the pump is disconnected. Depending on the terms of your sale and your state laws, you may have a claim against the seller if he disconnected the pump in violation of state emission laws and knowingly concealed it from you.

Nonetheless, as I mentioned in my prior post, I understand that in time the catalytic convertor can be damaged without the smog pump connected-- and as the convertor is a couple of thousand $$, it probably worth spending the $350 or so to fix the smog pump.