Engine Break-in, Blue Smoke

[Brad Bartilson]

Having same blowby (blue smoke) condition after installing new short block. Its strong enough to deeply annoy anyone following behind when I'm under load-starting out or going up a hill. I've got breathers on both valve covers. My data says I'm not running rich all the time (would cause "washing down of the oil off the cylinder walls). While I still get the same smoke, the oil is staying clean, unlike my old short block (diry oil was my reason for believing the rings never seated right on my last rebuild). I'll do a compression test, but how do you tell if its a valve guide? Is there a path significant enough to cause this through the PCV/vacuum hose system (to pass high pressure to the crankcase)? I only see them all teed up at the vacuum block atop the throttle body.

-Brad
bartilson@yahoo.com

 

[outback]

check turbos

i can think of a cople of things you could try im not formilure with the type of turbos on your car but if they are oil fed or some eople call them oil coled the seal could be gone on ither the intake side which would force oil through the engine and couse it to smoke or on the exsorst side wich would make it smoke all the time
it could also be valve stem seals bt it its a valve stem seal it would normally only smoke when first started and under load but very little just ideling
hope i was of some help james

 

[Brad Bartilson]

intake leak

Mechanic said it sounds like an intake manifold leak, to check this by plugging off the PCV and checking for vacuum conditions at the dipstick pipe. Will do this tonite. Also said that the high-temp RTV was the wrong stuff to use on the intake, that some "super seal" or special intake sealant from Felpro was the best to use, that my RTV stuff would never seal it. Anyone had similar experience with intakes not sealing?

 

[outback]

manifoldleek

i know on a natrial asprated car the manifold would get cold or be colder wher it is leeking and you could play around with the fuel mix and it would have little or no efect car would sometimes runn ruf would also have vacume problems bad braking due to low vacume

 

[Brad Bartilson]

Issue Solved!

Turns out it was a very badly installed oil pan gasket! Leaked so bad that allowed air to be sucked into the crankcase, causing oil burning out the exhaust. Amazing. Bad, bad mechanic. thanks all.

 

[turbosam6]

That is, I believe, mechanically impossible. Explain?

 

[Brad Bartilson]

explanation

I don't have a physics explanation. Several mechanics that thought it was a leaking intake said that anytime a crankcase is under vacuum, that an engine will burn oil. You could feel suction (vacuum) on mine by placing a hand over the valve cover opening. My oil burning went away definitively by fixing the oil pan gasket, no question. Just a thought why this would be: Upward movement of the piston means air volume is increasing in the crankcase. If there is a leak in the crankcase additional air is sucked in during this short period, which then must be compressed, perhaps this upsets the action of the oil ring.

 

[turbosam6]

Actually, putting the crank case under vacuum is good and helps STOP the oil burning (blow by) issue. Hence the reason many racers run a vacuum pump and why we have a PCV.

Who are these "mechanics"? Sounds like a load of BS to me.

 

[Brad Bartilson]

Sure interested in additional ideas, as simple sealing of the oil pan fixed the burning. I never saw vacuum conditions on the crankcase while idling. I'd also note that the action of the PCV assures that pressure doesn't build up in the crankcase. The crankcase is experiencing pressure pulses. Applying vacuum downstream of the PCV would assist in drawing the pulsed air from the crankcase. As to how much vacuum the crankcase sees, it would depend on the action of the PCV check valve. I also hear they're putting them on diesel-turbo devices as well, with a reservoir, mainly to avoid putting the oil-laden air back into the intake (stock situation on our car) or down a dump tube (diesel, which makes a mess). Only other thought I had is that my leak (and associated air draw-in point) is way down at the pan, obviously on the upstream side of the PCV (check valve).

As this oil burning only happened under good load, I couldn't check check for vacuum conditions while in the garage. I could have rigged up a guage in the car and observed the crankcase conditions while under load. However, now that its fixed, I've already eliminated the condition, and wouldn't be smart to recreate it to definitively know the answer.