m112 (clk320) mysterious valve cover - Mercedes-Benz Forum
 
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post #1 of 6 (permalink) Old 05-16-2019, 01:41 AM Thread Starter
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m112 (clk320) mysterious valve cover

hello everybody, can someone explain me what is the use of those smaller covers present on top of the main valve covers ?
while replacing the 12 platinums, i found them leaking oil, so i tightened all four torx bolts , they were very loose.
from that moment on, car is producing a bluish puff of smoke on startup, and then all is normal as before.
cannot fathom what could've happen.
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post #2 of 6 (permalink) Old 05-16-2019, 11:28 AM
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Search this forum, lots of info on these little valve breather covers for M112 and M113 engines. Remove them clean well and use Mercedes RTV sealer and new stainless steel allan key bolts for the small ones (old ones made of aluminium and can snap or strip when tightening)

All the rubber breather hoses if hard and brittle should also be changed.
Only be worried if your engine uses oil.
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post #3 of 6 (permalink) Old 05-16-2019, 12:21 PM
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There is a lot of information in the W210 Forum Stickys.

Here is one: https://www.benzworld.org/forums/w21...ion-error.html

Those bolts are there to hold the covers in place while the sealant dry. I would not tighten them to stop the leak. The valve cover is made of magnesium and the screw holes can strip easily.
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post #4 of 6 (permalink) Old 05-16-2019, 01:46 PM Thread Starter
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many thanks for the clues.
i will certainly proceed to check out those persky breather covers and EGR valve.
main valve covers are not leaking one bit, so I would not bother.

so,
do you think that such clogged egr hoses/small holes could possibly be the cause of the SMOKE at start-ups?
idle is not rough at all, and no error codes.

the car has only 135K kilometers, but it was neglected ,
no oil changes for 3 years, (!!)
since it was garaged all the time and only used very sparingly.
on purchase, i was horrified to discover such thing, the oil was indeed dark brown,
so I proceeded to an "emergency" oil change with a semi-synth 10W40 bought at a supermarket, (only oil, no filter)
since I had to drive the car back home for 1000km and could not stomach do the trip on such dark sludge.
car drives flawlessly, very fast and uses very little gas for a V6.
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post #5 of 6 (permalink) Old 05-17-2019, 12:13 AM
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Yes the small holes can block up especially on short journeys. 135 000kms is not even run in and brown oil (if synthetic) which has been there for three years is no problem. If it was pitch treacle black then I would be concerned.

I would leave the ERG valve alone - one can screw up badly here.

As I am doing low mileages these days I change oil every 2 years and it is still clean so thinking about changing every 3 years now. This is what synthetics were designed for- either high monthly mileage or longer periods between changes.

Obviously if you are driving 2 kms to the corner store every day in a harsh winter environment then oil needs to be changed more often.

Also ensure you use the fleece filters.

Just get the car out on the open road and give it foot - these M112s are remarkable engines, simple, reliable and efficient.

I would be more concerned with changing brake fluid every 2 years and the coolant every 3 years. Also change the transmission fluid now and then later every 50 000 kms. Change diff oil at 160 000.

Enjoy.
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post #6 of 6 (permalink) Old 05-17-2019, 02:46 AM Thread Starter
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thanks for the tips,
yes, i already changed all fluids and filters, 772.6 included, along with brake hoses, and i will replace again the oil , but this time with a full synth 5w40 and of course filter as well.
so i will open up the covers, clean'em well , replace alu bolts with steel. will also remove egr hose and clean if clogged, hopefully not.
yes its truly a remarkable engine and feels more powerful than 218 claimed hp... best v6 i ever owned, better than BMW I6 imo...
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