Curbing my enthusiasm, blow-by in a 1982 300D - PeachParts Mercedes-Benz Forum

300DPETE · #1 10-30-2005, 11:24 AM

Well, I thought I was doing okay. I have a 1982 300D with relatively low mileage (just under 147,000) that has been very well maintained by previous owners, is rust free, and runs great...perfect candidate for a nice VO conversion.

However, I did some blow-by tests this morning that weren't as encouraging or mixed at best.

Here were my tests:

--Oil cap loosened while running: a bit of "tea-kettle" action going on here with oil sputtering out a bit.

--Thumb on hose to air filter: shuts off in 6-8 seconds.

--Open end of hose to air filter: some steam coming out.

What I don't get, is that the air filter looks clean, and the air filter housing is dry other than a little bit of oil (maybe a silver dollar size of a thin layer) on the bottom of the housing.

.....Bummer. I thought I'd picked out a car in really good condition. Looks like the engine may only be so-so.

While it may run good now (starts in cold weather, doesn't smoke, etc.), it sounds like from the blow-by discussions on this forum that the engine life may be on the short side of a typical 617.

Pete.

pawoSD · #2 10-30-2005, 11:33 AM

Mine has had a similar amount of blowby the entire time I have owned it so far (from 207k to 230k currently) and it will start reliably without a block heater down to -10F, and it has a LOT of pep and power and will haul the car to 110mph no sweat. Mine dies after about 7-10 seconds of plugging the breather tube. I'd say, don't worry about it, just keep on changing the oil every 3k and enjoy the next 100-150k

I highly doubt your engine is even close to needing a rebuild.

1983/300CD · #3 10-30-2005, 11:39 AM

Adjust valves and timing. You might not be all that bad off. They have blowby when new.

300DPETE · #4 10-30-2005, 01:15 PM

Quote:

Originally Posted by Col.Klink

Everything you just described is quite normal for your Diesel Mercedes . Don't woory about it unless you have High oil consumption . The only efficient way of determining the overall engine condition would be to do a Cylinder Leakage Test which will tell the condition of each cylinder and its Sealing .

I don't think it consumes oil. It just scared me a bit when i saw the warning signs some have posted here that indicated "stay away." Thanks though, I feel a bit better (would be nice though if the cap didn't bounce, and it shut off after 20-30 seconds after plugging the hose to the air filter!).

How much would it cost to do a Cylinder Leakage Test? I was considering getting a used compression test kit, but it sounds like there's an additional step here I need to consider. Is this something I can do myself (the cylinder leakage test)? What additional tools would I need other than the compression test kit?

Thanks,

Pete.

300DPETE · #5 10-30-2005, 01:17 PM

Quote:

Originally Posted by 1983/300CD

Adjust valves and timing. You might not be all that bad off. They have blowby when new.

That's on my list, but I thought that valve adjustment doesn't affect blow-by. Is this not true?

Pete.

t walgamuth · #6 10-30-2005, 01:32 PM

technically if the valves are leaking the blowby would be less. i think.

tom w

iNeon · #7 10-30-2005, 09:23 PM

dont let the people here(even if they are immensly wiser than yourself...) scare you out of your own car.

i read a great deal before jumping into my 240d(a little less miles than yours) and didnt do ANY of the silly mechanic checks or even check the oil before i bought it.

i got lucky and got a decent one, but it has a lot of pressure in the engine(theyre supposed to, right?) and pushes oil out of many little holes in the engine. i add half a quart of oil bi-weekly because of it. it doesnt scare me, its an old car. even with 5 year old commuter car miles(150k or so) a 25 year old car is going to have more wear on it. more cold starts, more stop and go.

if the possibility of high repair bills scare you, these arent the right car for ya! i, myself, just relish every mile i spend with my shlomo and ill put a new engine in there when he absolutely stops running. until then, ill putter around with a big stupid grin on my face as i hold up someones soccer practice

#8 10-30-2005, 09:30 PM

I garuntee I have more blowby than you and my car still starts good and is a strong runner..

Don't get too easily swayed...there are more important things than a simple blowby test or two

300DPETE · #9 10-30-2005, 09:38 PM

Thanks, guys. I'll keep my eye on it, but will allow myself to swallow and breathe deeply now.

Thanks,

Pete.

P.S. I'll report on what adjusting the valves does next weekend.

300DPETE · #10 10-30-2005, 09:43 PM

....forgot to mention that the "thumb on hose to air filter" test worsens after driving the car (maybe 5 or 6 seconds). I take it this is do to higher pressures when the engine is hot? No?

Thanks,

Pete.

kerry · #11 10-30-2005, 09:46 PM

The shut down test is very unreliable in my opinion. A leaking gasket will lengthen the shut down time by decreasing pressure on a high blowby engine and tight gaskets on a low blowby engines will cause it to shut off quickly.
Precise measuring with a calibrated blowby measuring tool may have some relevance but until you do that and compare the results to engines in a variety of known condtions of repair/disrepair, I'd find something else worth worrying about.

300DPETE · #12 10-30-2005, 09:48 PM

Cool.

When you say gasket, do you mean the valve cover gasket?...the head gasket? BTW, what does a head gasket look like anyways? ....sorry, still learning.

BTW...I voted for you

1983/300CD · #13 10-30-2005, 09:51 PM

Well, okay. I guess it looks like you're right. I heard from someone that a valve adjustment would do some good for blowby, but it might not.

It seems that if the valves were leaking, they would leak either into the exhaust or back into the intake - not into the crankcase. (thanks Ken300D)

And if anything, poorly seating seals would decrease compression, forcing less blowby past the piston rings.