Oil blow by

[VGM]

This week I had two customers experience oil blow-by that covered their engines with oil. I did not build either engine, but both are just 1600 stockers. The first was a '69 Bus with a 1600 SP. He brought it in with oil everywhere and a quart low. I suspected the oil cooler. But after adding a quart of oil, a tune up and engine cleaning, there was no evidence of any oil leaking anywhere.I warmed it up and drove it around the block and it stayed bone dry. I checked the stock breather hose to the stock remote air cleaner and I could feel the crank case blow by escaping freely. After picking it up, he called back later to say that after a half hour of driving up the canyon, all at once the engine started smoking from oil covering it.
The second is a '66 Bug with 1600 DP and dual ICT webers. My customer had just purchased the car and has not driven it much yet. It came in with evidence of blow-by, again oil covering the engine. I assumed it must need more crankcase venting, so I installed valve cover vent tubes and used 1/2" id hose to connect to an Empi breather box located on the inner fender well above the left rear shock. I drove it around town a bit and had no evidence of blow-by oil problems. I get a call the next day and he says that after driving the car for about 1/2 hour, the oil covered the engine.
Both instances seem to share the common symptoms of driving for about 1/2 hour and then, all at once, the oil blows out (I assume from behind the crank pully) and covers the engine. Any ideas what is causing this and how I should approach curing it?
Thanks, David G.

[VGM]

Anyone?

[SCOTTRODS]

Anyone?

Doesn't sound like anything I'd call "blow by"...... Sounds like a leak that requires some pretty specific parameters to occur, and they only all happen at certain times in the driver's days.... Gonna be something hard to pin-point,.... but you can do it if you take the time and take things apart far enough to find the leak.

[goober]

We're they driving 45 mph in 3rd gear up a steep grade on a hot day when this occurs? How worn are the engines? Do they suffer from excessive blow-by?

[Jim Ed]

Anyone?

Try this link:
http://www.vw-resource.com/crankcase_ventilation.html


Here are some quotes from that link:
If you're not using the standard air cleaner, you may not be getting enough vacuum to suck the oil laden fumes up through the alternator stand, resulting in the mist blowing out backwards through the ventilation slots behind the crankshaft pulley. Take a look -- any evidence of the oil (streaking etc) inside the cleaner would indicate that it's pulling the oily air through properly.

You MUST have the tube from the oil filler connected to the air cleaner. The VW engine pulls in fresh air from slots behind the engine pulley - positive crankcase ventilation. This air, plus any "blow by" from the cylinders, is pulled into the air cleaner and re-burned.

Using an aftermarket air cleaner may reverse the pressure, causing oil to come out of the crankcase where air is supposed to be going in. If it's not a positive pressure, then there might be LESS vacuum in the air filter, resulting in a greater likelihood of more pressure inside the crankcase.

"Speedy Jim" suggested the following test -
Clean everything up real well to spot the source. Try this: At idle, remove the oil filler cap and hold it loosely over the opening. It should just flutter without really being blown away. If blown away, there is excessive blow-by.

Rob responded - Three other possible sources of oil leakage into the engine compartment have been suggested -- the oil pressure switch, the dipstick, and the oil filler. The oil pressure switch should NOT have a gasket or O-ring. Wrapping string around under the dipstick cap may help. The oil filler cap must fit snugly.

Dave took the problem of oil in the engine compartment to the RAMVA Newsgroup - A nagging question - What could be the source of oil on the engine tin around the rear of the engine? We've replaced the oil pressure switch and the distributor shaft seal and tightened the oil filler cap -- oh, yes, and packed string around the inside of the dipstick collar.

Bob Hoover wrote - You may have a blow-by problem. The annular orifice around the pulley hub is the normal INTAKE for the crankcase ventilation system. Outlet is via the dynamo tower to a low pressure area inside the air cleaner. But when you lift your foot -- close the throttle -- there's no low pressure to maintain air flow through the crankcase. If you've got a blow-by problem -- leaky rings or, more likely, worn valve guides -- the pressure inside the crankcase can be great enough to defeat the oil slinger, blowing a gust of oily vapor out the inlet where the pulley does a nice job of distributing it around the engine compartment.

[VGM]

Thanks-good info!