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Old 27-07-2021, 09:48   #1
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Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

Afternoon all,

I'm working on a 2013 Leopard 48 and trying to help the owner figure out next steps for his generator - Northern Lights OM773LW3 with 8,940 hours on it.

Background/Issue:
- The owner reported that previously the dipstick would pop out causing oil of course to escape and go all over the place. He would of course replace the lost oil yet the issue persisted.
- He bought a new, tighter fitting dipstick figuring the one there had slowly worn and that was the cause of it fleeing its post.
- Oil loss continued and eventually oily residue was found in spots along the head gasket.

The Question:

- Is it possible that the head gasket was slowly failing, which caused blow by to increase, which then pressurized the crank case enough to blow out the dipstick? Is there a way to diagnose or definitely answer this?

- The fear/hesitation with moving forward with the head gasket replacement is that whatever pressurized the crankcase previously enough to cause the dipstick to pop out will just then cause the new head gasket to fail again in short order?


Tests/Notes So Far:
- Opened lower oil fill while generator under load, don't have a manometer on board but definitely felt air puffing on my hand.
- Visible oil residue around head gasket
- Checked air filter and intake - clean, no apparent, issues, no clogs
- Checked crank case vent - clean, no apparent issues
- No milky oil
- No oil in coolant
- Has not overheated with the current owner (though could have in the past)

- Are there any other simple tests that I'm missing prior to moving forward with a head gasket replacement?



Thanks in advance for the collective knowledge!
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Old 27-07-2021, 10:05   #2
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

Check compression or better do a leak down test if you have the equipment.

Check the crankcase ventilation hose for blockage. Most of the go to the intake manifold these days.
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Old 27-07-2021, 19:54   #3
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

Hi mkjones. I have a feeling that thereís a filter and an internal drilling across to the air intake in the rocker cover. This is whatís on the NL673 so it might be the same on the OM773, practically the same engine. Crankcase pressure usually comes from worn piston rings or as you suggested, a blown head gasket across to the pushrod gallery but start with the easy stuff..... take off the valve cover and see if that crankcase ventilation setup is blocked, maybe adjust the valve clearances while the lidís off.
Pete.
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Old 27-07-2021, 20:07   #4
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

Quote:
Originally Posted by mkjones View Post
Afternoon all,

I'm working on a 2013 Leopard 48 and trying to help the owner figure out next steps for his generator - Northern Lights OM773LW3 with 8,940 hours on it.

Background/Issue:
- The owner reported that previously the dipstick would pop out causing oil of course to escape and go all over the place. He would of course replace the lost oil yet the issue persisted.
- He bought a new, tighter fitting dipstick figuring the one there had slowly worn and that was the cause of it fleeing its post.
- Oil loss continued and eventually oily residue was found in spots along the head gasket.

The Question:

- Is it possible that the head gasket was slowly failing, which caused blow by to increase, which then pressurized the crank case enough to blow out the dipstick? Is there a way to diagnose or definitely answer this?

- The fear/hesitation with moving forward with the head gasket replacement is that whatever pressurized the crankcase previously enough to cause the dipstick to pop out will just then cause the new head gasket to fail again in short order?


Tests/Notes So Far:
- Opened lower oil fill while generator under load, don't have a manometer on board but definitely felt air puffing on my hand.
- Visible oil residue around head gasket
- Checked air filter and intake - clean, no apparent, issues, no clogs
- Checked crank case vent - clean, no apparent issues
- No milky oil
- No oil in coolant
- Has not overheated with the current owner (though could have in the past)

- Are there any other simple tests that I'm missing prior to moving forward with a head gasket replacement?



Thanks in advance for the collective knowledge!
Wowser, 8 years and 9000 hours? Dipstick popping out? I'd say run hard and put away wet too often. I'm guessing rings and a lot more once it is apart.

I'll add that the owner received 9000 hours of value in exchange for the purchase price. Cobbed back together it will not yield another 9000 hours. Just overhaul the thing and be done with it.
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Old 27-07-2021, 20:50   #5
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

Do a compression test first. Most generators are started and immediately go to operating rpm. No warm up. Thick, cold oil doesn't lube well until warmed. Probably a compression test will show loss of compression. You're also probably putting a sheen on the water.
One possibility is if the generator was run for many hours at light load. The cylinders could be glazed. The fix is a light honing of the cylinders and new rings.

I doubt it's the head gasket. 9000 hours are a lot of hours for a light duty generator engine. I'd plan on a rebuild or a new engine. Since the engine is still being made, it may be cheaper to buy another engine than do an overhaul unless the owner can do the work. An then you have spare parts from the old engine.

Generator end bearings are usually replaced at 5 years. Check that, too.
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Old 28-07-2021, 09:21   #6
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

9,000 hours says it all. Generators I have been involved with have never lasted more than 10,000. Sure compression test would be my first move and expect to rebuild.
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Old 28-07-2021, 09:25   #7
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

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Originally Posted by Stewie12 View Post
9,000 hours says it all. Generators I have been involved with have never lasted more than 10,000. Sure compression test would be my first move and expect to rebuild.
Lepke is probably more right than we are. They should just get a new engine and save the trouble. Maybe one of the sparkies on here can tell us if the generator and other bits ought to go over the side, too.
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Old 28-07-2021, 09:29   #8
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

I have rebuilt generator engines keeping the generating part and never had a problem. If the generator part works fine, no need to change it.
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Old 29-07-2021, 05:31   #9
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Re: Northern Lights OM773LW3 Blowby, Head Gasket, Oil Loss - Diagnosis Help

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Originally Posted by Lepke View Post
Do a compression test first. Most generators are started and immediately go to operating rpm. No warm up. Thick, cold oil doesn't lube well until warmed. Probably a compression test will show loss of compression. Generator end bearings are usually replaced at 5 years. Check that, too.
In doing a compression test... after you have done the compression test, squirt oil in the cylinder and repeat the compression test. If the rings are worn the compression reading will be much higher.
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