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preservedkillick 08-09-2009 08:53 AM

Leaking intake gasket caused by too much blow-by?
Motoring yesterday, 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 that goes from the cover to the intake manifold (near where I think the leak is), if I take put my finger over the end of the hose with the engine running, within a few seconds I can feel the pressure building up. What's normal?

This sounds bad. Rings? Valves? Any chance there's a valve somewhere, like a PVC valve? I don't see one.

This seems to be a sudden thing, it's been running well, with no sign of trouble before yesterday.

This is a 10 year old diesel Vetus 310 with less than 400 hours reported.

timebandit 08-09-2009 10:01 AM

Partially plugged exhaust system or valve adjustment?

Selkirk 08-09-2009 03:25 PM

I think you're actually looking a little too far into the woods. I believe all you have is a failed gasket.

Why did it fail? I dunno. But it did, and that's the first thing I'd fix.

preservedkillick 08-09-2009 03:27 PM

I thought of those two things too. Valves..I'll get a mechanic if it comes to that. I'll check the exhaust elbow when I go back this week.

I've done some research, and it appears that some blow by pressure is normal. Based on what I've read in the diesel car forums, lots of pressure along with smoke is a bad thing. But, I wonder, what is considered normal. I'm not getting any smoke that I can see, although I did get a little soot near the leak.

I don't think I'm burning any oil, although I can only say that I've burned none in the 20 hours or so I've put on the engine since I've owned it. Oil looks ok, coolant looks great. Both changed this spring.

Thinking more about it, I don't quite get how the gasket could have failed as a result of the blow by. Granted the leak is at the intake manifold right near where the blow by hose connects, but the intake manifold should have no pressure..the air intake is right there.

My plan so far is to check the exhaust elbow, replace the leaking gasket (if I can get one from Vetus) and keep an eye on it. I'd also like to get a compression test done.

Capnblu 08-09-2009 09:26 PM

If your intake manifold gasket is leaking, it would be a vacuum leak. Blow by refers to combustion gasses entering the crankcase, past the piston rings. If your exhaust valve stems were leaking, you would have some blow by into the valve cover, but not much. If your intake valve stems were leaking, you would be pulling oil into the combustion chamber, and probably notice smoke in the exhaust. I suspect your exhaust manifold / heat exchanger gasket is the culprit remove it clean the surfaces, and install a new set. Torque to mfg. specs, and then after 10 - 15 hrs, retorque.

trantor12020 08-11-2009 08:08 AM

your exhaust manifold or mixing elbow is choked.

preservedkillick 08-18-2009 09:11 AM

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 negine 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.

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