These two pictures are of two different compressors, the one with the 4 bolt mounts and a sensor on the back is for the W124 chassis E300D (OM606)

The other one which has only 3 mounting bolts is for the 1996 and ahead E300D which are the W210 chassis.

Whilst both engines are the same, the compressor for the AC are different. Make sure which one do you have.

Attached Thumbnails

   

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Your original AC compressor will bolt up directly to the 606 engine block. I have done 5 606 to 140 chassis conversions I did the original conversion while I was on the Mercedes club forum. This was the first successful conversion of 603 to 606 posted to any forum.

__________________
Joe Tripp
Mercedes Club member since '76
Continuous Mercedes ownership since '64.
'93 300SD 111,000 miles. Now has '99 E300 engine.
'94 S350 77,000 miles
'95 S350 148,000 miles.
'96 S420 159,000 miles.With '99 606 Diesel. Sold
'99 S600 one of 14 imported. Sold.
'89 Bentley 8 40,000 mi. Sold