Lehman 120 seized - where should I spend my next 10-20k?

[warfdog]

Update to the drama and what I hope is good news.

#6 Cylinder broke free after carefully soaking in Kroil and gentle scraping and cleaning with a shop vac - bore looks pretty good to me, only issue I see is pitting on the top of the piston (2nd attachment). Getting it to move was not hard with a coupled of bumps on the starter followed by repeating wiping down and spraying the groove in the cylinder wall with oil.

Engine spins over very easily. There was a little aluminum oxide showing on the #6 cylinder wall but no gouges. As the piston moved I cleaned the oxide on the wall constantly. It took about 2 minutes to completely clean it and get it to move freely. (Cylinder damage to the skirt is possible ??)

In fact Cylinders #5-4-3-2-1 don't look any different than #6 Now (3rd-4th attachments for example).

Head is off and at American Cylinder Heads in Oakland CA American Cylinder Head Inc - Cylinder Head Sales and Repair (they do lots of boat and truck heads and will check for cracks and recondition it as needed for about $500). The last photo is not very clear but you can see the water damage on #6 exhaust port - hope we don't find any cracks.

I'm a bit concerned about the manifold as well. I'll need to clean it up and see what it looks like. Any after market manifolds available?

Maybe with a moderate honing the cylinders can be acceptable after checking for roundness. Can the pitting on the #6 piston cause problems - should it be ground or sanded smooth, or better left alone? What are the chances that the damaged piston causing havoc later?

By the way did you know that spinning the motor will pump a bunch of oil up the passages to the head and blow diesel fuel from the lift pump in your left ear?

I'll let my mechanic take the ball from here but any advice is appreciated. I'll be calling Brian at ADC up for supplies on Monday. He's been helpful so far by phone but not responding yet to my emails.

Thanks all,
Cap'n Warfdog (Joe)

 

[warfdog]

Is the manifold higher than the exhaust /sea level

My exhaust elbow is 6-12" above the water line and goes into a water-lift muffler that has a lift of about 18". The run to the exhaust outlet is about 20' straight downhill from there and the outlet is slightly above the water at light loading.

 

[SteveK]

4-5-6 excess heat. That sounds like a clogged coolant circulation. The #6 issue came up on some searches when I went searching for my seized engine. Since I did not have the seized valve, well you know the rest.
But I do not recall if the coolant circulation blockage was in the head or block, question for Brian.
Also the #6 is usually lower than others due to slant, so any water backing from exhaust could get in there. There was a discussion here about if the engine does not start quickly close the through hull until it does.

 

[SoWhat]

Where did the water come from?

The pitting didn't happen overnight. Suspect water has been sitting there before. You just happened to let it sit long enough to finally seize. If it was running well prior to this, then I'd be tempted to run with it.

Removing pistons and honing cylinders is a major rebuild for experienced mechanics. Specialized equipment and measuring instruments. I would be tempted to get a diesel mechanic to take a look at it and give you an opinion.

Your halfway to a rebuild by removing the head.

 

[Albin]

#6 exhaust valve was frozen

But you said that Brian from "American Marine" (he's actually the owner of American Diesel Corp) said that running it hot would ruin #6 cylinder. There was no mention of a frozen valve at that point in the conversation. Why would running it hot only affect #6 cylinder?

 

[BruceK]

4-5-6 excess heat. That sounds like a clogged coolant circulation. The #6 issue came up on some searches when I went searching for my seized engine. Since I did not have the seized valve, well you know the rest.
But I do not recall if the coolant circulation blockage was in the head or block, question for Brian.
Also the #6 is usually lower than others due to slant, so any water backing from exhaust could get in there. There was a discussion here about if the engine does not start quickly close the through hull until it does.

Fairly sure the clogging or "silting" occurs in the block. (Does it come from old coolant?) No. 6 is furthest from the circulation pump, No.1 closest. I think the block coolant chambers will need cleaning, there are proprietary flush products which may help.We had it on the port engine several years back, mechanic said it took several flushes to clear it. I recall Brian saying in a bad case you could remove the freeze plugs( called welch plugs here), they`re in the block.

 

[Albin]

Post 3 above may help.

Thank you. I didn't see that post in my first read through. Good to know.

 

[SteveK]

Fairly sure the clogging or "silting" occurs in the block. (Does it come from old coolant?) No. 6 is furthest from the circulation pump, No.1 closest. I think the block coolant chambers will need cleaning, there are proprietary flush products which may help.We had it on the port engine several years back, mechanic said it took several flushes to clear it. I recall Brian saying in a bad case you could remove the freeze plugs( called welch plugs here), they`re in the block.

Thanks Bruce, that was my concern, the head will be cleaned, the OP has to be sure to clean the block too or the head work will be wasted with a repeat event

 

[Ski in NC]

The concern is that the piston rings in #6 could be stuck in the grooves from corrosion. Best is to drop the oil pan and pop the piston out to clean it up, and to clean the bore, and some new rings.

There is a pretty simple test for stuck rings: Put #1 and #6 about 1/4" from tdc and wiggle pistons sideways in bore. There is a few thousandths of an inch play in the pistons relative to the bore and rings will shift in their grooves. Compare how 1 and 6 feel. If #6 rings are stuck, you will feel less movement. Can also probe the rings with a 0.002" feeler to see if it extends below the top ring (but don't break it off!!). Solvent and heat on the piston crown can loosen stuck rings (sometimes), but still best to pop piston out. No fun putting head back on and realizing rings are stuck.

Any sign of water in exhaust manifold exhaust passages?

Block water jackets can be cleaned out with a skinny tube on a shop vac inserted down through fire deck coolant holes.

Coolant residue in pics looks pretty crappy, lots of Fe oxide visible.

Surface pitting on piston crown should not cause any trouble. Worry more about stuck rings.

 

[twistedtree]

To me this looks much more like a water incursion problem than an overheating problem. The exception would be if the overheat caused excessive expansion and a leak between head and block. Is that how this known Lehman "#6 overheat" problem typically presents itself? At a minimum I would give the exhaust a careful inspection. You said the exhaust loop was 6-12" above the water line, and I believe 12" is typically the minimum. So sounds like yours in marginal, if not below spec?

 

[Alisske]

The concern is that the piston rings in #6 could be stuck in the grooves from corrosion. Best is to drop the oil pan and pop the piston out to clean it up, and to clean the bore, and some new rings.

There is a pretty simple test for stuck rings: Put #1 and #6 about 1/4" from tdc and wiggle pistons sideways in bore. There is a few thousandths of an inch play in the pistons relative to the bore and rings will shift in their grooves. Compare how 1 and 6 feel. If #6 rings are stuck, you will feel less movement. Can also probe the rings with a 0.002" feeler to see if it extends below the top ring (but don't break it off!!). Solvent and heat on the piston crown can loosen stuck rings (sometimes), but still best to pop piston out. No fun putting head back on and realizing rings are stuck.

Any sign of water in exhaust manifold exhaust passages?

Block water jackets can be cleaned out with a skinny tube on a shop vac inserted down through fire deck coolant holes.

Coolant residue in pics looks pretty crappy, lots of Fe oxide visible.

Surface pitting on piston crown should not cause any trouble. Worry more about stuck rings.

+1 on the above, but I did want to thank the original poster for posting and the follow up. This type of post in invaluable and hopefully none of the rest of us will have to ever experience this. But if I do, this article will keep my anxiety down.

And the quote “ By the way did you know that spinning the motor will pump a bunch of oil up the passages to the head and blow diesel fuel from the lift pump in your left ear? ” is hysterical and true. I think anyone of us would have learned that the same way you did. (I picture you laser focused on the cylinders moving and not GAF about anything else, lmao.

 

[Alisske]

Oh. One thing I don’t think anyone has mentioned in this thread (but have mentioned Many times on other threads) is the exhaust elbow.

It has a shelf that rusts out (recommended changing interval is 2 years I think, but I get by on three hear in the northeast)

Once the shelf rusts out, it will dump water down into cylinder #6. This could be the reason for the rust/pitting. You could run that way for a while and would not realize it.

 

[SoWhat]

The concern is that the piston rings in #6 could be stuck in the grooves from corrosion. Best is to drop the oil pan and pop the piston out to clean it up, and to clean the bore, and some new rings.

Surface pitting on piston crown should not cause any trouble. Worry more about stuck rings.

Good point about the rings. High probability they are rusted. Assuming that's why the engine wouldn't turn over. Would filling the cylinder with light oil eventually loosen them up via seepage?

Worst case the rings scrape the oil film off and eventually ruin the cylinder bore. Not a good scenario. I have to agree that #6 at a minimum needs to be removed.

 

[KnotYet]

Update to the drama and what I hope is good news.

#6 Cylinder broke free after carefully soaking in Kroil and gentle scraping and cleaning with a shop vac - bore looks pretty good to me, only issue I see is pitting on the top of the piston (2nd attachment). Getting it to move was not hard with a coupled of bumps on the starter followed by repeating wiping down and spraying the groove in the cylinder wall with oil.

Engine spins over very easily. There was a little aluminum oxide showing on the #6 cylinder wall but no gouges. As the piston moved I cleaned the oxide on the wall constantly. It took about 2 minutes to completely clean it and get it to move freely. (Cylinder damage to the skirt is possible ??)

In fact Cylinders #5-4-3-2-1 don't look any different than #6 Now (3rd-4th attachments for example).

Head is off and at American Cylinder Heads in Oakland CA American Cylinder Head Inc - Cylinder Head Sales and Repair (they do lots of boat and truck heads and will check for cracks and recondition it as needed for about $500). The last photo is not very clear but you can see the water damage on #6 exhaust port - hope we don't find any cracks.

I'm a bit concerned about the manifold as well. I'll need to clean it up and see what it looks like. Any after market manifolds available?

Maybe with a moderate honing the cylinders can be acceptable after checking for roundness. Can the pitting on the #6 piston cause problems - should it be ground or sanded smooth, or better left alone? What are the chances that the damaged piston causing havoc later?

By the way did you know that spinning the motor will pump a bunch of oil up the passages to the head and blow diesel fuel from the lift pump in your left ear?

I'll let my mechanic take the ball from here but any advice is appreciated. I'll be calling Brian at ADC up for supplies on Monday. He's been helpful so far by phone but not responding yet to my emails.

Thanks all,
Cap'n Warfdog (Joe)

Joe, if your mechanic recommends pulling the block for a rebuild I would do it.
At the very least I would remove piston #6 and lightly hone the bore and remeasure.
The pitting on the piston top may be acceptable but the rings should be renewed.
I would look at this as an opportunity to bring your engine back to 'new' condition.
One day your life may literally depend on the reliability of this iron soldier.

 

[albinalaska]

TBD - probably lift the engine a few inches and refill the stringer under the engine with either a) coosa/marine-ply and thickened epoxy or b) sea-cast. I'm leaning toward sea-cast. Then cap with a strong fiberglass layup (either polyester or epoxy resin mix).

The whole area of compromised stringer(s) is very accessible and is only a portion of the overall stringer matrix.

I’ve been watching a rebuild channel on YouTube where he determined through some computer modeling software that if he layed up 5-7 layers of biactual it would compensate for the rotten stringers and provide enough support to give decades more of stability and use.

 

[BeeJay]

Update to the drama and what I hope is good news.



#6 Cylinder broke free after carefully soaking in Kroil and gentle scraping and cleaning with a shop vac - bore looks pretty good to me, only issue I see is pitting on the top of the piston (2nd attachment). Getting it to move was not hard with a coupled of bumps on the starter followed by repeating wiping down and spraying the groove in the cylinder wall with oil.



Engine spins over very easily. There was a little aluminum oxide showing on the #6 cylinder wall but no gouges. As the piston moved I cleaned the oxide on the wall constantly. It took about 2 minutes to completely clean it and get it to move freely. (Cylinder damage to the skirt is possible ??)



In fact Cylinders #5-4-3-2-1 don't look any different than #6 Now (3rd-4th attachments for example).



Head is off and at American Cylinder Heads in Oakland CA American Cylinder Head Inc - Cylinder Head Sales and Repair (they do lots of boat and truck heads and will check for cracks and recondition it as needed for about $500). The last photo is not very clear but you can see the water damage on #6 exhaust port - hope we don't find any cracks.



I'm a bit concerned about the manifold as well. I'll need to clean it up and see what it looks like. Any after market manifolds available?



Maybe with a moderate honing the cylinders can be acceptable after checking for roundness. Can the pitting on the #6 piston cause problems - should it be ground or sanded smooth, or better left alone? What are the chances that the damaged piston causing havoc later?



By the way did you know that spinning the motor will pump a bunch of oil up the passages to the head and blow diesel fuel from the lift pump in your left ear?



I'll let my mechanic take the ball from here but any advice is appreciated. I'll be calling Brian at ADC up for supplies on Monday. He's been helpful so far by phone but not responding yet to my emails.



Thanks all,

Cap'n Warfdog (Joe)

Good news that #6 was near TDC. Makes you wonder if it would be a good idea to bar the engine over to have #6 sitting at TDC on the compression stoke (both valves closed) before a lengthy layover. Or would it result in seeing issues with #5 with the same conditions.All the best with the rebuild, I think you can get away with a fair bit with these lumps. You just need to work out where the water came from.