Hi-

I have a 1984 190d 2.2 with 4 cylinder engine (non-turbo) that has a small hole in the cylinder head cover on the passenger side. According to the manual, this is to vent the diaphragm chamber in the pressure control valve (see pic below) It smokes a lot through that hole and when I'm idling, the smell gets blown into the car through the climate control air vents. Pretty smelly and nasty.

Does anyone know if I can
1. block this hole (on another 190d I looked at, the hole appeared to be hidden/blocked with a sticker); or
2. reduce the smell through the climate control vents by another means? I don't know where the climate control vent draws the air from, so perhaps I could make sure it's not drawing in the smoke.

Any ideas would be most appreciated. Thanks.

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I like the smell at idle, it's the only time I get to appreciate the smell of the biodiesel I use. The rest of the time it's wasted on the ga$$er behind me

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

I wanted to point out that the smell is burning motor oil and not diesel/biodiesel.

Does the motor smoke alot under the hood?

__________________
1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

Not a huge amount, but there is a steady stream of smoke from the "vent"

The hole is there so the regulator in the valve cover knows what atmospheric pressure is. It needs to know that so it can properly do its job of regulating the suction from the turbo inlet that pulls vapor out of the crankcase. Smoke coming out suggests that there's something wrong -- with the regulator or something else.

Boooney, do two tests for us and report back:

(1) with the engine warm and idling, remove the oil filler cap. Do you get a huge cloud of smoke/vapor (blowby) from the valve cover?

(2) Put the cap back but don't tighten it. Does the cap dance around like the lid on a teakettle?

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Jeremy,

I did these tests already. There is a fair amount of blowby and oil splatters outside of the oil filler when I remove the cap. The cap does rattle around a lot like the lid on the tea kettle.

By the way, this car isn't turbo, so does it need the hole for the turbo inlet that pulls vapor out of the crankcase?

Thanks.

Mercedes probably had a good reason for designing it with one.

The reason I'm asking is because I have seen another 190d without the hole and it works fine...

Shouldn't it be hooked up to an oil sep or a draft tube or something?

__________________
1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

My 190d 2.5 turbo has the same hole and it's a very annoying one as when it spits oil outside.

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1992 Mercedes 190D 2.5 turbo 5sp manual. EGT+boost gauges. Boost controller set to ~14.5 psi. 1 1/4 turns on full load adjustment. LPG injection. Next in the list is water injection.

Your relatively high level of blowby may mean that the pressure inside the valve cover is more than can be handled by the "PCV" system. The excess pressure is escaping any way it can, by going through the vent. Another possibility is that something is wrong with the vent system (hose collapsed or plugged up) and the blowby is escaping through the little vent. Better that than blowing a seal, I suppose.

Engines that don't have a vent in the side of the valve cover probably use a different type of oil breather. The vent hole is not hooked up to a tube because it's designed only to let the pressure regulator sense atmospheric pressure. In a new engine, the regulator keeps intake vacuum from pulling oil out of the crankcase. In an engine with very high blowby, all bets are off.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Jeremy,

This is great info. Thanks. I expect that there is extensive blow-by. As a last resort, how do I check for a clogged vent?

With the engine idling, pull the plastic vent hose out of the intake pipe and see if crankcase vapor is coming out of it. If you have as much blowby as you say, it should be spouting like The Little Engine That Could.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Vent Hose: Do you mean the black plastic hose on the top of the engine?