Simplicity 4041/ onan CCKB Engine question

[Gcabinet1 16]

I am puzzled by something that I discovered when I took the oil cap off when the engine was running!

I got a huge pressure release ( pressure and oil) is this normal? Do I have a clogged vent or bad breather tube.

i also have a loud valve tick, thanks for any light you can shed on this.

[Gcabinet1 16]

In other words what would cause high crankcase pressure 

[midnightpumpkin 83]

On 11/10/2016 at 9:05 PM, Gcabinet1 said:

I am puzzled by something that I discovered when I took the oil cap off when the engine was running!

I got a huge pressure release ( pressure and oil) is this normal? Do I have a clogged vent or bad breather tube.

i also have a loud valve tick, thanks for any light you can shed on this.

Opening the oil fill cap on a running Onan is something you only do once. I believe the oil spray that comes out is perfectly normal. As for the valve tick, I would change the oil to Rotella T 30W, with a 1/2 quart of Lucas oil stabilizer, it just might quiet down.

John U

 

Edited November 12, 2016 by midnightpumpkin
typo

[isetta 50]

Mine has a similar action when I pull out the dipstick.  The horizontally opposed twin layout moves a lot of air when the pistons come in but seems like would be balanced somewhat by the suction created when they move back out.  It may well be that it is balanced until one removes the dipstick and this allows the pressurized air an easy path to escape.  Might just be fine when the dipstick is in place.  I have considered that I may be using too heavy an oil:  20W50 and also that this oil may accumulate in the breather.  I considered making an auxiliary breather like seen on racing or off road vehicles to temporarily make it very easy for the engine to breathe and see what happens then when pulling the dipstick. 

[macallis180 296]

I've never taken mine off while engine is running - guess it's a good thing I haven't!

[Gcabinet1 16]

Thanks John I'll try the Rotella/Lucas

[720nut 4,225]

Don't know if you guys have checked the leak down on your engines but would be one thing I would deffinately do, as rings are probably getting worn and allowing leak by.

If your breather is clogged it also would cause pressure build up, most often when an engine starts building pressure the rings are to blame.

Just my $.02