Heyo

So I pulled the oil cap off the valve cover today after I noticed some seepage around the cap and it looks like there's blowby. I definitely didn't have this problem when I first got the car and I'm wondering what could be causing it? Oil was always changed right on schedule, and the valves have not been adjusted as long as I've had the car. I'm hoping it's something very simple that I'm missing.

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Never be ashamed to ask for help.

1985 300D
1987 300SDL
1970 Jaguar E-Type OTS
2002 Dodge Intrepid (Traded In)
2011 Ford Crown Victoria

Well, I'd say since you say the valves have never been adjusted, go ahead and get that done first

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1983 240D, 272K+ miles (odo broke)

I've got the new gaskets and wrench set, all I need is time. I'm currently studying for my Series 7/63 exams for work, so all my spare time is essentially spoken for.

Sorry for the seemingly ignorant, open ended question that's about to be presented: What causes blowby? I've heard people say they have it and continue to drive their cars, and that it's basically normal for a high mileage diesel to have it. Mine's only at 177K, so I guess I wouldn't be expecting blowby to be a regular occurance until the 230-240K mark. Unless I'm wrong about this, too? This is a time I'm hoping for a solid Tangofox explanation

__________________
Never be ashamed to ask for help.

1985 300D
1987 300SDL
1970 Jaguar E-Type OTS
2002 Dodge Intrepid (Traded In)
2011 Ford Crown Victoria

Replace the gasket material on your valve cover cap and get on with your studies. Nothing to worry about unless its losing large quantities of oil.

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You can't always get what you want, but if you try sometime you just might find you get what you need.

Can you tell what your oil consumption is? I have a car with similar mileage and a tad bit of blow by with pretty much negligible oil consumption over 3,000 miles (I don't have to add any between changes). If your oil consumption is okay I wouldn't worry about it, but definitely adjust those valves!!

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1983 300CDT -- 177K

+1.

There is always a little "blow by" as engines wear, and if your oil consumption is fine, don't worry about it.

Blow by is caused by worn piston rings. As the rings wear, and don't seal as well as they used to, some of the pressurized gas slips past the rings on the compression stroke, and pressurizes the crankcase. This escapes thru the oil filler cap when you remove it.

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Chief

1991 350SD

Blowby is essentially positive crankcase pressure. This is mostly caused by gasses slipping past the piston rings or valves. Gasses slip past piston rings for a variety of reasons, including mechanical wear, foreign materials adhering to the cylinder walls (e.g. varnish, carbon), stuck rings, and other reasons.

In general, being unable to maintain 100% gas containment in the piston chamber is what causes blow-by. Blow-by is essentially an informal mechanism for determining the general health of an internal combustion engine.

Internal combustion engines are basically air-pumps that run on the concept of gas energy and movement. The inability to maintain gas seal means that the engine is not as efficient as it could be.

The obvious issue is that if you have blow-by, it means that the combustion cycles are not optimal, and you are wasting energy that cannot be recovered to propel the vehicle.

This only becomes disastrous if you are unable to compress the air enough to achieve fuel-air mixture combustion, or the energy output is so low that the vehicle effectively ceases to function.

In general, if you have adjusted the valves (thus making the valves seal as best they can in their current state) then you have no other solution to reduce blow-by short of a ring job/engine overhaul, if mechanical wear is the issue. If foreign debris or build-up is the issue, then an Italian tune, coupled with solvent soaks, solvent mixtures in the fuel and crankcase oil, and viscosity enhancers are pretty much your options.

Once you've tried those, if it really is just a worn engine, then I say "change oil and drive it!" (and stop worrying about it)

Sincerely,

PE

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

By the way, you didn't state which engine you were talking about. I'm sure you already know, but the 6 cylinder 603 engine has hydraulic lifters and aren't adjustable.

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Chief

1991 350SD

See the initial subject of the post. But I should have restated it while describing the problem so I apologize.

__________________
Never be ashamed to ask for help.

1985 300D
1987 300SDL
1970 Jaguar E-Type OTS
2002 Dodge Intrepid (Traded In)
2011 Ford Crown Victoria

Here is a Blowby test.

Engine blow-by test, Blow a bag of blow-by

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works