That makes a lot of sense.

If an engine hasnt been run for a while, once it is run for a while could blow by decrease at the rings get used more and maybe some of the crap is burned off?

How can the oily blow by be reduced other than a ring job? Is there anything that could be done?

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Here is a trick that may reduce some of the oil in the blow-by off the valve cover vent. Sometimes the oil return galleys from under the valve cover on older engines get clogged up like arteries to and from your heart. This prevents the oil from returning back down to the oil sump fast enough and the valve cover gets flooded out. The extra oil gets splashed up into the oil seperator in the cover and goes out with the Blow-By.

An old gear head told me to use a guitar string (low E with the Brass wire wrapped around it) like a long pipe cleaner and hone out the crud/tartar from the return oil galleys. You can run the guitar string all the way through to the sump in some holes. Then he said to run the engine to flush all the crud you knock lose to the pan and then change the oil. It works great if thats your problem....and can reduce smokey exhaust and oil consumption.
Hope that helps!
Cheers

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

Fred,

Thanks for the suggestion. I will try this at some point.

Its very interesting to hear about these 'other causes' of blow-by.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I am surprised that nobody has picked up on F18's tip. These older Diesels that consume oil could greatly benefit from this tip. I will try it on mine at next Valve Adjust time. All of the experts have been claiming for years that it is due to Valve Guide wear. I cannot buy this explanation when an engine is using 1 qt per 300 miles and there is no blue smoke ever.

Something that has not been stated. Some "blowby" will always occur due to the movement of the pistons up and down and acting as an airpump in the crank case. It is a dynamic situation that does not fully self-cancel. In addition to this is the contribution from gases coming past the rings and the vaccuum pump discharge as already noted. In general blowby is a very poor and unreliable diagnostic and this has been noted in some of the threads dealing with compression.

Please jump in here some of you guys since I want to learn more on this topic. The info on the industrial large diesel engine explosion feature was very informative.

I don't know about later vacuum pumps but the claim that the vacuum pump vents into the crankcase on the early model vacuum pumps seems false. The early model vacuum pumps have a line that vents into the top of the air cleaner.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13