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Discussion Starter #1
Hi everyone,

Been a bit since I've posted on here. My beloved daily driver is a 1995 E300D, has 250K on the clock, taken me many places and survived 3 girlfriends.

needless to say, a keeper of a car.

I went into the engine bay today to stop a small fuel leak from #5 DV on the injection pump, and am having serious thoughts about deleting the PCV mechanism.

The engine had a serious fuel overhaul/IP swap last year about this time, and has decent compression, but is not a race machine or perfect. I use this car for the copious highway and city driving I do. I have rental properties, and spend lots of time on the road.

Anyway, the PCV system has never really been leak-free, I had it patched into the valve cover with RTV, which worked pretty well for a year, although it was ugly.

Its clearly been leaking, as I had a little oil in the crossover pipe when I popped if off today, and some oil mist/dirt is collecting on the top of the valve cover.

My question is this: what's the harm in deleting the PCV recirculation system and just venting it out the back of the car? I've done this with my powerstroke diesel, and it eliminated the oily mess in the intercooler pipes, and the mess at the junctions as well.

Is there some magical Mercedes reason why nasty crankcase gas needs to be injected right at the intake valves?

I'm religious about 3000 mile rotella changes, and a can of Restore, and use liqui-moly SDA in every tank. Engine (after I muddled my way through timing it right) fires off instantly every time, and purrs like a kitten.

Someone correct me if i'm about to do something stupid, but it seems like clean air and clean fuel is the proper diet for a diesel....??
 

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W124 diesels are exempt from smog checks, even in treehugger crazy California.

In addition, the W124 diesel does not have a PCV system. Instead, they have a CCV (crankcase ventilation) system.

On the '95, the CCV just consists of the little tubes and rubber elbows underneath the black plastic shroud that sits atop the valve cover.

If I were, and this is what I did, just leave the EGR in place but remove the oxidation catalyst. More than likely, it is clogged and robbing power.

Use Liqui Moly SDA (super diesel additive) with each fillup and it will clean out the entire intake tract including the CCV system.
 

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First of all, you would need a lot of plumbing to vent it all the way out the end of the car. Second you will need 12 rubber plugs for the intake manifold to completely remove the vent tubes. I also have a 95' E300D. with 180K. I haven't seen any issues with leaving the system alone. MY EGR valve died years ago and that's the one that causes the buildup in the intake manifold.
I agree with the liquid Moly diesel purge. But I do it once every 6 months directly from the bottle for a flush.
for the fill up I use Opti-lube diesel additive.

Jetguy
 

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Plug the holes in the intake manifold and vent the crankcase into the airbox. Venting it to the back of the car will leave an oily mess and in smell nasty in the car every time you stop at a light. Ask me how I know. If you're plugging holes in the manifold this is also a good time to block off the EGR and clean out the intake manifold with a pressure washer. This is what I did to my 97 (606.912).
Plugged the 12 holes in the manifold with 12 small sheet metal screws topped off with some silicone. Most of the plastic fittings at the manifold were already broken allowing unfiltered air to leak in. Ran a hose from the stock oil separator (round thing) to a catch can on the driver's side.


Hose goes from valve cover to catch can on the right intake horn on the left.


Clean out the intake manifold and block off the EGR. The combination of EGR soot and oil will kill air flow through the manifold and reduce power.
 

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EGR on a diesel is definitely detrimental to the intake system as it reintroduces exhaust soot back into the engine with negligible reduction in emissions. I completely removed the EGR on my 82 300D W123 with the OM617 diesel. The intake was a mess, just like pictured above. I had a machine shop clean it up and reinstalled it. Unfortunately, I could not clean the intakes on the head.
 

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EGR on a diesel is definitely detrimental to the intake system as it reintroduces exhaust soot back into the engine with negligible reduction in emissions. I completely removed the EGR on my 82 300D W123 with the OM617 diesel. The intake was a mess, just like pictured above. I had a machine shop clean it up and reinstalled it. Unfortunately, I could not clean the intakes on the head.
I did it with a bent butter knife on an OM603 and OM606. It was ehh... super fun.
 

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Discussion Starter #8
@sbaert - thank you for clearing up the difference in PCV vs CCV. Was not aware of the notation. Also, Oxy cat is gone. Made a HUGE difference.
@tjts1 - thank you for those photos, they are really helpful. I currently have mine routed down by the driver's front wheel well, but seeing what you did with the catch can, I like that better. Cleaner looking setup, and I don't like oily messes.

What was the hose that you used? Looks to be some type of braided line? Got a link or a place to source it?

I used a combo of RTV and 1/2" "emission plugs" from napa to close off the holes. My intake manifold is pretty clean after the extensive job last year, and with the liqui-moly at each fillup, has remained so. Valves are also cleaner since I started using it.

AZ does emission test diesels, but its on a dyno, and is opacity test. A joke to pass.

As always, thank you to everyone on here. great forum!
 

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Discussion Starter #9
And yes, EGR block/delete was one of the first moves I made when I got this thing. Those are terrible and coke up everything.
 

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I don't remember the type of hose, braided industrial something or other 1/2". It was left over from another project. Not exactly automotive grade but its held up ok.
 
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