That new van burning smell – DPF regen

When you smell burning under the hood of your brand-new Sprinter, don’t panic. It’s probably your first Diesel Particulate Filter (DPF) regeneration cycle. During the first regen, the filter reaches very high temperatures and burns off any paint, body undercoat, or Waxoyl that might have dripped on it during manufacturing.

The owner’s manual is light on details about DPF regeneration. They say that if you mainly drive short distances, you should drive on a highway for 20 minutes every 300 miles. That suggests that the regeneration cycle happens about every 300 miles, but in real life we’ve found it to be between 500 and 750 miles typically.

So you’re likely to encounter your first regeneration at about 500 miles. You’ll smell burning, and if you get out of the van and stop the engine you’ll hear the click-click-click of hot metal cooling down.

DPF filter location on exhaust pipe
DPF filter location on exhaust pipe – front of van is to left of picture. DPF filter is near the right front wheel.

Mercedes would never admit that their vans stink, so you won’t see anything about smoke or noxious fumes in the manual. However, these are quite likely during the first couple of regeneration events.

Basically, the Diesel Particulate Filter is heating up and burning soot out of the particle filter. It’s not the soot that you smell, just any rubber body undercoat or Waxoyl (the yellow coating they spray on exposed metal) that dripped on the unit during manufacture. Once it’s burned off, the smell will stop.

Ironically, if you do what most sane drivers would do when they smell burning, you probably stopped the engine and thus stopped the regen cycle mid-flow. That means it’ll have to try again later to finish the cycle.


7 Replies to “That new van burning smell – DPF regen”

  1. Thank you! Again. It seems that whatever keywords I type in for a Sprinter related issue, you always have good answers 🙂

    1. At least one of the Bluetooth OBD applications I wrote about here has a field for DPF regen that seems to be accurate. The OBD Fusion app has a “DPF regen status” gauge that shows “0” unless a regen is happening, when it shows a “1”.

      I’m not sure there’s much you can do with that information though. You could conceivably keep driving until it finished, but the odd missed or incomplete regen probably isn’t going to kill your DPF filter.

  2. Hi just wondering does this process smell like electrical burning like hot wires my sprinter I just purchase a few weeks ago is a ex postal van it’s done about 240,000.My wife was driving it home the other night and when she go home and got out of the van she could smell this strange smell out side the van on the right hand side cannot smell it inside the van at all and the van runs and drives and appears to be normal but have this weird electrical burning smell anyone have any suggestions??

    1. Lee, the DPF smell only happens for the first couple of times the van does a regeneration. After that, the drips of undercoating and other stuff have burnt off. It can smell a little like hot electrical insulation, but I don’t think that’s what is happening in your van.

      Because your van has 240k miles on it, the smell is most likely caused by something else. It *might* be that some road debris has got stuck against the exhaust system (plastic bag or similar) or it *might* be that the previous owner sprayed new undercoating on the van to hide some rust, and some got on to the exhaust system, but more likely it’s a different problem entirely.

Leave a Reply