Leaking Intake Gasket Caused by Too Much Blow-By?

[Killick]

Hi Everyone,

I've got a 10 year old Vetus M3.10 diesel in my sailboat. Boat is new to me, the engine has less than 400 hours. It ran great, so far..until yesterday when I noticed the smell of exhaust in the engine compartment. Took a look and it appears to be leaking exhaust out of the intake gasket. Bit of black soot near where the leak is.

Now, when starting the motor, there's a distinct "air sound" before it actually fired up. There's a blow-by hose (crankcase breather hose?) that goes from the cover to the intake manifold near where I think the leak is, if I put my finger over the end of the hose with the engine running at idle, within a few seconds I can feel the pressure building up. What's normal? No smoke just pressure.

This seems to be a sudden thing, it's been running well, with no sign of trouble before yesterday. Since the engine is new to me, I've been constantly checking the oil, looking for potential issues, adjusting idle speed ect, and noticed nothing until the leak happened.

Could the pressure from the vent hose have blown the intake gasket? Attached to the intake manifold is the air intake so there shouldn't be any pressure there, correct? Could I just have an old gasket that needs replacing, or more serious issues.

Calder's book suggests checking the crankcase vent hose under full load, I checked it at idle. Would my test be meaningless since the engine is at idle? Wouldn't the pressure increase under load?

[Chief Engineer]

Make sure the engine is not over filled with oil.

Blowby can be caused by bad rings, bad valve seal or bad valve....

[fareweather]

Took a look and it appears to be leaking exhaust out of the intake gasket. Bit of black soot near where the leak is.

Are you positive it's the intake? If you have enough ex gas coming thru the intake to blow the gasket and leave sooty marks you have a significant problem. Something more than just high CC pressures. Possibly a plugged silencer/ex system?? Calders book explains how to clean a typical silencer. Check/clean ex mani/elbow as well.

there's a distinct "air sound"

That sounds like a disconnected intake, without the air filter on it can sound "throaty" check all your connections.

What's normal?

Should increase with RPM, absolute pressure depends on condition of engine. CE explains where that pressure comes from.

Could the pressure from the vent hose have blown the intake gasket?

Not likely, the CCV hose would likely separate first.

Got pics??

[Killick]

Just a follow up.

Went to the boat, ran the engine and could feel pressure & exhaust coming from the intake manifold gasket. Replaced the gasket, didn't change a thing. Checked exhaust mixer elbow, clean. Running the engine again, feeling more carefully, found an injector near intake manifold was leaking. Took the injector out, found carbon gunk at the bottom where it seats on a copper ring. I cleaned up the carbon as best I could and put it all back together..runs fine. I had no idea an injector could leak like that.

[fareweather]

Good to hear it was an easy fix. The washers are copper crush washers/heat shields, prolly a good idea to get a few to keep around, they are cheap. Generally speaking they are considered single use but most reuse them. When you torque down the injector they conform to the head and injector base forming a tight seal.