Excess Crankcase Pressure Causes?

[98TsiAWD]

I blew out my dipstick the other day and also suddenly started leaking oil out my oil feed line where it connects below the turbo (connects the 2 lines together, but its nto the fitting that leaks).

Excess Crankcase pressure is what I think.

My PCV valve is good and the hose and/or fitting are not plugged either.

My valve cover breather is not plugs and either is the fuel filter I have on it or the hose.

So what else can cause excess crankcase pressure?


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[98TsiAWD]

bump.

 

[NDgsx]

Ring sealing problem. What's your compression?

 

[98TsiAWD]

Originally posted by NDgsx
Ring sealing problem. What's your compression?

I did a compression check, however my spark plug hole temp was only 125 degrees F. So I did it with the engine not as warm as I should have so my numbers are a little lower than they actually are.

Cylinder 4- 155psi, 6$ leakage, 2%oiled (4% variance)
Cylinder 3- 141psi, 27% leakage, 22.5% oiled (4.5% variance)
Cylinder 2- 140psi, 24% leakage, 18% oiled (6% variance)
Cylinder 1- 150psi, 14% leakage, 8% oiled (6% variance)

As you notive putting oil in there doesnt make alot of difference in my leakage so the rings are in pretty good condition.

Doing the leakage test I came up with that my intake valves are not fully closing (noise out of throttle body). I am running through injector cleaner and will probly use MOPAR combustion chamber cleaner also to try to fix that problem.

What else can cause it? I am going to bypass my PCV valve today to help get the pressure out, I dotn want to crack anymore oil lines or oil seals inside the engine.

 

[NDgsx]

Run both lines to a catch can and eliminate the PCV, that's what I would do.

 

[98TsiAWD]

Originally posted by NDgsx
Run both lines to a catch can and eliminate the PCV, that's what I would do.

Yeah, I just put a clear fuel filter on the pcv just now, I put a 1/8" pipe fittin into the pcv valve cover hole. The fuel filter I use have a plastic can around them that cathc the oil, then when it starts to get oil in there you just dump it out. Works kinda like a catch can in a way.

 

[98TsiAWD]

Go here: http://www.pbase.com/str8ballin/pcv_bypass for pics of my bypass.

 

[dsmntc]

If you think it is carboned up to the point its affecting valve sealing, it is very possible that your top rings are sticking in their grooves. This could explain the ok compression readings, but the marginal leakage results. The ring does not seal by virtue of its slight spring pressure against the cylinder wall, but rather by gas pressure forcing against the back of the ring. If pressure cannot get behind the ring due to carbon build up, the ring will not seal well. Also carbon can cause the ring to stick in the groove and cause a temporarally huge pressure leak into the crankcase.
Also, what does the compression go to on the first "puff" this is a very good indicator of ring sealing. and should be at least 50% of the total number. Try a chemical cleaner like you were going to, and it may just help out, but then address the problem of why the carbon is so heavy in the first place! Good Luck,
Pat

 

[98TsiAWD]

Originally posted by dsmntc
If you think it is carboned up to the point its affecting valve sealing, it is very possible that your top rings are sticking in their grooves. This could explain the ok compression readings, but the marginal leakage results. The ring does not seal by virtue of its slight spring pressure against the cylinder wall, but rather by gas pressure forcing against the back of the ring. If pressure cannot get behind the ring due to carbon build up, the ring will not seal well. Also carbon can cause the ring to stick in the groove and cause a temporarally huge pressure leak into the crankcase.
Also, what does the compression go to on the first "puff" this is a very good indicator of ring sealing. and should be at least 50% of the total number. Try a chemical cleaner like you were going to, and it may just help out, but then address the problem of why the carbon is so heavy in the first place! Good Luck,
Pat

The compr. numbers on the first puff were about 5spi lower than the end number, so definately in the 50% margin.

 

[dsmntc]

That high on the first puff seems almost inplausible, but that certainly steers away from ring wear. Blow by is the most common cause of excessive crankcase pressure. Other factors are, plugged c-case vent system (even the hose nipples themselves), head gasket failure between cylinder and oil return port (would have low comp on affected cyl) Badly worn valve guides( this can also cause poor seating of the valves, and is worth a look with your symptoms)
Pat