Bypassing air pump

I went to start this heirloom, daily driven, Benz, heard belt noise and observed smoke coming from under the hood. I opened the hood and noticed the air pump pulley was frozen, the smoke was the belt being friction fried!! My mechanic informed me I could belt bypass the air pump, and the air conditioner compressor, which I agreed to as a quick fix. He also informed me that in MA a 1990 car is exempt from emissions testing and bypassing the air pump the car would surely fail that test.

Here’s my question since the check engine light is now occasionally on. Is any damage being done by driving the car without an air pump, are the sensors and computer able to handle what is now shitty emissions?

The only damage that’s being done is to our atmosphere. But even with the pump working, the difference is insignificant. Drive on…

Thanks for the feedback, a plus was increased MPG by not running the pump and AC compressor

If your secondary air injection pump is needed to get your vehicle into “closed loop” operation, you do indeed have a driveability problem and your problem is greater than increased pollution for the rest of us.

I am not in favor of disabling any emission system, you may be shortening the life of your catalytic converter by operating your vehicle as so described.

Thanks for the feedback,

You can removed the pump. I’ve done it on numerous vehicles.

Thanks for the feedback.

In addition to potential issues described above, permanently disabling the air pump and AC is a step to ‘heapdom’, where you figure out reasons not to keep you car in good shape. Temporary? OK. Permanent? Not what I’d do to my car, ‘heirloom’ or not.

The secondary air pumps purpose is to inject air into the exhaust stream to light off the catalytic converter(s). Without the air pump the catalytic converter(s) will eventually plug up and will have to be removed or replaced.


Thanks for the feedback, yes temporary

Thanks for the feedback.

Since the car is exempt from emissions testing, you might as well “De-Smog” the whole thing (I.E. remove the converter) but since an oxygen sensor is still controlling the fuel mixture, converter plugging might not be an issue…

Or you could be a good boy and remove the pump and soak it in a bucket of kerosene with a quart of ATF mixed in and see if you can free up the internally rusted air-pump. They are a simple, durable, cast iron vane pump. The vanes can stick (rust) to the pump housing. Sometimes you can break them loose and you are back in business. The pump has virtually no drag on the engine so fuel mileage is not an issue. As Tester said, the pumps purpose is to supply some oxygen to the exhaust stream so the converter has something to work with. Today’s more sophisticated systems no longer need this added oxygen, or it is introduced without the need for a pump…

Noooo - I strongly recommend against desmogging. By 1990 these cars were well designed to work well with the smog equipment. Just the wrong thing to do.

I really appreciate all of the feedback. The car has only OEM replacement parts as it will be with the air pump. So can the car be driven daily for another month or so set up this way? I’m not feeling there is a sense of urgency, the feedback is mixed.

I would think that after driving the car for a month or two you will be running a chance of destroying one of your catalytic converters if it has more then one. It will be your gamble! You might check on the cost of a catalytic converter before you decide to run your car for a month or two.

The smog pump will be heart-stopping expensive, as are most Benz parts…So it’s worth a try to free it up. These things are NOT built like a Swiss watch, they are pretty crude and can survive a little neglect…

Thanks for the feedback. I’ll try soaking it this weekend.

Thanks for the feedback.

You also might try Ebay and auto recyclers for a used one.

Thanks for the feed back.