Blow By

[230slhouston]

Does anyone know how to measure blow by and what is acceptable?

A videos of acceptable blowby?

Thanks

Maistran (MB)
230sl

[Paddy_Crow]

Blowby is not easy to measure. First thing, you need a tight engine- no air leaks from the crankcase. Then you need a means of measuring air flow or velocity. Just hook the flowmeter up to the breather hose.

Then after you measure it you have to figure out what is normal.

If you're concerned about your rings, it's probably easier to do compression and leakdown.

[Benz Dr.]

On a tight engine there isn't that much and you won't see any smoke - just clean air coming out. On a really worn engine it will come out in a steady stream and will be quite visible.
Think of a kettle at full boil if the engine is under some load. You should also see a a fair amount of smoke out the exhaust but some engines don't smoke all that much yet are still worn.

Don't confuse this with a cold engine where there might be some condensation or steam escaping out of the valve cover vent. Once the engine warms up there should be little or nothing coming out of the pipe.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[230slhouston]

My compression is within spec, no smoke at all but there is condensation at start up, actually even when warmed up. I thought it was water getting into the oil but I have no water loss or when looking at the dipstick, it is clean as a whistle, no water or sludge.

I did a test, took of the breather and routed into a collection bottle, after 50 miles, there was some condensation accumulated in the bottle, no oil or sludge. Is this normal?

Thanks

Maistran (MB)
230sl

[Paddy_Crow]

What's coming out the crankcase, for the most part, is combustion gasses. Lots of carbon dioxide and water vapor, among other stuff. It is normal for some of it to condense in a breather system. The more you slow the gas flow down, the more condensate you'll get.

[Benz Dr.]

That's normal.  I think I was once told that a gallon of fuel will produce ABOUT a gallon of water as a by product of cumbustion. Some of that water gets into the oil pan while the engine is cold and will form acids. There are neutralisers in the oil that will combat this but driving your car for short periods in cold weather is considered severe use. This is why you should use the correct thermostat in your car and make sure it runs at least 80C.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[J. Huber]

I wonder if this may explain why they changed the breather hoses from metal to plastic over the years. My original breather hose is metal but has corroded from the inside out due to that watery muck that gets spewed out.

James
63 230SL

[Paddy_Crow]

Another reason for using plastic is that it's less prone to icing in cold weather. And it costs less to make, too!

[Benz Dr.]

On a cold day you will see what looks like smoke coming from the exhaust pipe on your car. Most of it is steam and as the car warms up it will tend to go away. If it's really cold out you will still see some but it will still be far less once the engine is fully warmed.
I can tell if a car has a broken thermostat just by watching the exhaust. It will continue to blow steam even after the car has been driven for hours in cold weather. This is NOT water coming from the cooling system but is a product of cumbustion.

I can also tell if a car has a broken o2 sensor by the rotten egg smell as it drive in front of you or if it's passing you.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061