Oil Catch Tank (Oil Catch Can / Oil Separator) for Mercedes Sprinter: Eliminates Engine/Emissions System Failures
My Mercedes Sprinter is in the early stages of self destruction from oil vapor contaminating the EGR (Exhaust Gas Recirculation) system, PCV, turbo, DPF, etc. In spite of using high-grade oil and changing frequently. Well, I hope it is the early stages and not a rapid-onset thing.
At right, the readout is from the BlueDriver @AMAZON OBD dongle and app. It is essential to know when the DPF is regenerating so as to not cause it to keep failing and trying. Failures to regenerate can cause severe problems up to and including engine failure. Stop-and-go traffic, short trips, flooring the accelerator, high altitude, etc can all cancel DPF regen, causing the system to try over and over (and to not try until the vehicle is turned off and restarted).
The oil vapor contamination problems affect all Sprinters to varying degrees—“loose” engines will see problems sooner (including total engine destruction), “tight” well sealed engines broken in properly will defer those issues much longer (less blow-by).
In my 2017 Mercedes Sprinter, the Diesel Particular Filter (DPF) is doing a “regen” every 114 miles on average, which means that it goes ~114 miles normally, then regenerates for 20 to 40 minutes (~20 to 40 miles), then does it all over again! It should be every 500 miles on the highway. The regeneration puts considerable heat stress on the entire engine and emissions systems. Each regen consumes extra fuel, dilutes the crankcase oil (“fuel accretion” as noted in the manual), and generate extreme heat that rapidaly ages and damages components. The NOx sensors are the first to fail for me. And you could die from carbon monoxide emitted from a crack in the exhaust system.
One sign of the problems that I did not recognize starting two years ago was the “no go” problem. This is very likely caused by a clogged EGR system (oil vapor deposition), where things get coked-up/clogged and stick shut. I have no proof of this without getting the EGR opened up and inspected, but it is by far the most likely explanation.
2021-09-21, by Tom Stephens of Stephens Service Center. firstname.lastname@example.org, 916.715.0665
The following comments are my own opinions. After 50 years working with and for Mercedes-Benz as a Mechanic, Shop Foreman, Instructor, Service Manager and Shop Owner I retired in 2018. I no longer have any affiliation with Mercedes-Benz or its authorized dealers.
Catch Tank: The emission control laws say crankcase combustion vapor cannot vent into the atmosphere. When the engine’s running the crankcase combustion gases must be self contained. The engine has to recycle the crankcase vapor. The BlueTEC has a PCV valve that sends the crankcase vapor into the Turbo where it continually recirculates through the EGR and the air intake system. Mercedes has updated the PCV valve 14 times. It will need to be replaced on all 2018 and older models.
Eventually oil sludge coats the air intake track. The only way you can keep this crud from building up in the air intake is with high quality oil, frequent oil changes and a Catch Tank. Catch Tanks are approved by the EPA. Mercedes cannot deny your warranty if the Catch Tank is installed properly and appropriate for the engine. The problem is, no one makes a Catch Tank specifically for a BlueTEC diesel. However, there is a billet Catch Tank that works perfectly. It removes all the dirty crankcase oil vapor that normally goes into the Turbocharger. After the dirty crankcase vapor goes through the Catch Tank only clean air is returned into the Turbocharger. The Catch Tank keeps hot oil vapor from getting into the DPF. The cleaner you can keep the DPF the fewer times it needs to regenerate. I’ll say it again, it’s the extreme heat required for burning off the soot and oil vapor in the DPF that does much of the damage to a BlueTEC.
WIND: a key non-mention above is that while a catch tank keeps all systems in place and reduces emissions, it does insert into the PCV hose line, and thus is technically not in compliance with CARB (California Air Resources Board). Thus California Sprinter owners might have difficulty finding a shop to install a catch tank. A classic case of over-regulation causing environmental damage by not allowing technologies to reduce it.
I want a catch tank installed, but shops in California don’t want to touch it, due to to CARB (California Air Resource Board) regulations. The catch tank captures 99% of oil vapors. It reduces emissions and keeps all system components much healthier, further reducing emissions over time. It also means far less frequent DPF regen cycles which in and of themselves are polluting events due to large amounts of fuel being dumped into the engine to create the extreme heat needed to do the DPF burnoff regeneration (“regen”).