DEF pump replacement
 

This is the second time I have replaced the DEF (Diesel Emissions Fluid) pump on this R320 (friend Dave's car). I made the mistake of buying a Chinese copy (Dave did not want to spend the money on a Bosch, he is selling the car). It only lasted a few months. It leaked internally (fluid in electronic parts), and caused multiple trouble codes. He "bit the bullet" and bought a genuine Bosch. It is actually not a bad job, and only took about a half hour. The ML, R, E or any other DEF equipped vehicle should be about the same, as far as the procedure goes for changing the pump. The first step is to make sure the tank is low or mostly empty, so the fluid will not spill out when replacing the pump. If you are replacing the heater, the tank should be removed from the vehicle. If just the pump, no need to remove the tank. Next, remove the outer shield, and lower the tank onto a stand of some kind. I had a lift available, so that made it much easier. After removing three wiring connectors and feed tube from the pump, a hex key (Allen wrench) is used to remove the three socket head cap screws holding the pump to the heater. I used a nut driver on the short side of the key to gain more leverage. Remove the pump, and install the new pump in reverse order. I found it easier to install the larger rubber washer in the heater, and the smaller Oring on the pump. These come new with the kit, as well as new screws. As seen in the photo, the fluid was coming out of the pump from where there should be none, and crystallized. The last step is to clear all the trouble codes. You could also view the live data (if your scanner is so equipped) to make sure the pump is working..........Rich

How many miles on that R320? My GLK is at almost 90k miles on the original adblue equipment (all of it) still going strong....

I follow the proper full drain/replace of the ad-blue every 2 years or less (every other fill of it).....don't want crystallized junk going into the pump.

The R was purchased a couple years ago at about 140,000 (I think it was a good deal, it is very clean), and soon after, things started going bad. I don't know for sure, but the Adblue pump might have been the original one when I replaced it with the Chinese knock-off. The first thing to go was the power steering pump, then the DEF heater (I should have replaced the pump at the same time), then the rear bulb sockets (replaced them with the modified ones), then the rear SAM, then the DPF needed cleaning, then the fuel supply and return hoses and filter replaced, the serp belt and idlers took a dump next, and then the DEF pump got replaced again. The driver side front door lock motor still needs replacing (got a used one on ebay). Other than ALL of that, the car has been great!
Dave bought the car upon my suggestion, and it has been a money pit since. However, I think the common problems have been addressed, so the car should give him many trouble free miles (at least I hope it does!). He wants to sell it, but the market for these is really soft. He may not get near what he has into it. It is very nice to drive, but it is just an extra car for him, so it does not get driven much. If anyone needs a "GOOD" R320 Bluetec, please let me know, I know where there is one for sale!