560SL Air pump

[embe560sl]

Does anyone know the need for this pump? My newly acquired 560SL made a terrible grating noise on start up and couldn't figure out what it was. It only lasted 10 seconds or so and then quit. I discovered eventually where the noise was coming from ...this unit. I took the drive belt of it and it solved the problem. Is it necessary for proper engine function?....... cause damage without or just an anti pollution thing?

[lesrrt]

Your aip pump is designed to operate by pulling air from the air breather and pumping it into the exaust side of the heads; This, in turn, heats the exaust gases quickly during early start-up. Thus, lowering HC emissions. Once the O2 sensor becomes heated, the solenoid to the airpump diverter activates redirecting the air to the breather. By taking the belt off, you disable the air pump effecting your early emissions. It will heat up itself w/out the pump. I took mine off and plugged the heads with the european dowells when I rebuilt the motor. If your state doesn't have the insane emmision laws and look under your hood, I would leave it off...the belt that is. Hope this helps.

[embe560sl]

Thanks for your input feel much better about understanding what it was doing.
When you state "plug the heads" ....what did you mean?

[rwogs]

My 1995 E320 89,000 mi started this 2 weeks ago. I used a stethoscope to trace it down to the air pump (located above the alternator on the pass. side of the engine). The links I've read tend to indicate that it is the bearing associated with the pulley on the electromagnetic clutch which is independently replaceable. I found a very reasonably priced site (ordered a full pump today and am waiting for the part) which will sell you the clutch/pulley or the whole pump.
www.mbpumps.com
If anyone is interested I wil post my experence with the site.

[lesrrt]

Hey embe. If you were to remove the intake manifold, there is a channel that directs air to each of the cylinder heads with a 6mm hole leading down to the exaust port of the head. The CDmanual describes putting dowells into these orifices with locktite to permanently close the passages. If you remove the pump and one-way diverter valve on the engine, the engine will sound as if there is an exaust, leaking percussion sound coming from the fitting on the engine. Instead of the dowells, I tapped the holes to 7mm and fitted 7mmhead screws in. 2 for each with plenty of loctite while I had the heads off. That way, carbon won't build up towards the intake. Euro models w/o pumps are set up this way. Since the car lives at 2400-2600 rpm at 65-75 mph, I don't anticipate a carbon build up. However, the emission Nazis would differ; there are some here... Hope this helps

[Walrus]

Originally Posted by lesrrt

Your aip pump is designed to operate by pulling air from the air breather and pumping it into the exaust side of the heads; This, in turn, heats the exaust gases quickly during early start-up. Thus, lowering HC emissions. Once the O2 sensor becomes heated, the solenoid to the airpump diverter activates redirecting the air to the breather. By taking the belt off, you disable the air pump effecting your early emissions. It will heat up itself w/out the pump. I took mine off and plugged the heads with the european dowells when I rebuilt the motor. If your state doesn't have the insane emmision laws and look under your hood, I would leave it off...the belt that is. Hope this helps.

Let me add to this that the pump has a magnetic clutch which will disengage at 70C water temp,as it is no longer needed with the engine aleady warm... You may just want to unplug the clutch, if the bearing is still good in the clutch.

[embe560sl]

Thanks all for your input, I think I will just keep it unbelted...no harm done is there?