Topic: Blow-by?

[Rob the plumber]

I was wondering if any of you guys can check something out for me. With my oil fill cap removed and the engine idling, there is a significant amount of air coming out. I am guessing that I may have some worn rings and the crankcase is being pressurized. I see just a little dark spot on the back of my air filter though.
I have not got into the throttle at all with the turbo yet so I really don't think I popped anything.

I was considering removing the oil pan, and trying to sneak each piston out from the bottom and replace the rings that way. I don't know if the crank can be spun out of the way though.

So if any of you guys could remove you oil cap while your Jeep is running and post the results, that would be great.

Thanks!
Rob

[VA_YJ]

The standard way of checking the rings is to perform a compression (pressure) test on all cylinders.  You should do this with the engine warmed up.  If one or more cylinders reads low, then you have something (worn rings, valve, head gasket, crack) that is leaking.  To figure out if it's the rings, you put a teaspoon full of oil into the leaking cylinders and repeat the test.  If the compression goes up after you add the oil, the leak is caused by poor ring seal.

I don't like your idea of rebuilding the engine through the bottom end.  You need to measure (or feel) the bores to see if they're tapered - (more wear at the top than the bottom).  If tapered, you may need over bore and oversize rings.  Even if not tapered, when you replace the rimgs, you should crosshatch (diagonal hone) the cylinders to ensure good ring seal.  The fastest, easiest way is to do it right the first time.

[aw12345]

A compression test is good, a leak down test is better. Taking the pistons out of the bottom hardly ever works the casting webs for the crankshaft main bearing interfere with the piston, nor is it necesary to see if the rings are worn, a leak down test will give you a pretty good idea whats going on without disassembling anything.
Now if the engine never burned a lot of oil check the crankcase ventilating system, which most likely doesn't work under boost since it relies on intake vacuum, might hyave to re plumb it. Aleak tester can be bough cheap at harbor freight, try it, its a good tool to check engine condition and doesn't cost more than 40 bucks from the tool truck should be a fair amount less from harbor freight. It does need a compressor to work though

[Rob the plumber]

I just performed a compression test and got 130 psi in 3 cylinders, and 125 in one cylinder. It took 2 cranks to get there. I don't know if that is within specs or not. It does not seem too bad.

[Bounty Hunter]

It may not be blowby, could be your CCV system is clogged.  What year jeep?

To check the CCV, pull the airbox end of the tube from the airbox to the valve cover.  The tube should be sucking air through this tube into the valve cover.

The CCV is easily clogged by carbon buildup in the restricting orifice or by collapsed lines.

[aw12345]

The compression is good

[Rob the plumber]

The CCV line is clear. I have it running to the inlet side of my turbo, and the compressor side of the turbo is getting a little oily. I am going to Seafoam it and see what happens. I am also going to remove the plugs and pour Seafoam into each cylinder. I'll let it soak in there for a day and spin the crank back and forth by hand a few times to try to get the stuff into the rings.

[aw12345]

It might just be normal for your setup any positive crankcase ventilation system relies on some manifold vacuum to work. You go down the road with boost in the manifold it will not draw the fumes and oil mist into the intake anymore which is what its intended purpose is to burn these fumes instead of venting them into the outside air

[Rob the plumber]

Maybe i'll suck out the blow by with a crankcase EVAC system. Cheap, easy, and effective as long as my exhaust flows well. This engine will really never be run at banzai WOT. Mostly part throttle where the exhaust system should be fine with an EVAC system.

[aw12345]

There you go, as long as the engine doesn't douse it self in oil from improbable places, the blowby would not be excesive. You know what I mean if you ever seen an engine that keeps taking a magic oil bath but doesn't really have any apparent oil leaks