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Old 02-03-2014, 02:04 PM   #1
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Apparent overheating Ford Lehman 120

One day after an afternoon out motoring on our 1979 Defever 43 we pulled into the slip and I got ready to shut down the engines. I noticed a knock in the port engine.

I checked the injectors at a local shop and they were ok. No indication of coolant loss, and water was exiting the exhaust. Impeller had less than 50 hours. Exhaust elbow was fairly new. Oil looked ok. Had to bring in a mechanic at this point.

To make a long story short, the #6 piston was destroyed and the cylinder scored evidently due to overheating. This came as quite a surprise as the temperature gauge had not indicated an overheat situation. So we replaced the piston and rod and honed the cylinder. Started right up and sounded fine. About 5 hours later the knock was back. We ran into Bob Smith at the Fall MTOA rendezvous and he came aboard and listened. His thought was maybe the water jackets were clogged from running the engines at 1400 (low) rpm, which I do, but have the mechanic check it out.

The mechanic returned and said the cylinder was scored in the same place as before. We removed the rear freeze plug and the water jackets were clean. So I'm out about 4 boat units and no closer to solving the problem than before and still have a sick engine. Anybody have any thoughts?
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Old 02-03-2014, 02:47 PM   #2
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This problem has been mentioned before and I had thought it was probably clogged water jackets in the back of the block. But now you say that wasn't the case w your engine. I don't know anyone here that works a FL hard and has little or no cooling problems. You need to hear from that person (IMO) or persons ... preferably persons. If they exist your problem may not be engine design but something else. But IF it is engine design a solution needs to be found.

I had a Sabre 120 that is supposed to be the same Ford block and I heard mine was blueprinted to mil specs and should be capable of very heavy loads. So it's hard to imagine a cooling problem in such an engine.

So I suspect that Lehman dropped the ball when they marineized the 380 Ford engine.

Does the coolant run aft on one side of the block and return on the other? That's hard to imagine. Perhaps there's just not enough flow back at cyl #6 for some other reason.

Perhaps drilling a hole on the back of the block and screwing in a pipe thread to hose bib fitting and plumbing the hose to an appropriate place like the intake of the water pump so the flow past and/or around the back of the block would substantially increase. Perhaps a simpler fix can be conceived that would solve the more or less well known problem. I offer my thoughts as food for a better idea.

I believe there must be a problem and if Bob Smith hasn't come up w a solution there may not be such a problem. But if there is and BS hasn't addressed it TF members would seem to be ripe candidate for finding a solution to the probable problem. At least those that have FLs. That could be over 50%.

Another thought is that your cooling system has another problem that reduces the performance of your cooling system over-all. The #6 cyl being a weak link your engine runs hot and it shows up at the #6 cyl but you've said the engine wasn't hot. Perhaps your gauge wasn't telling you the truth. Something simpler like this is probably at fault and a combination of 2 problems is even more likely.

Also Bob S may have been right and you just couldn't see enough of the water jacket to observe the blockage.
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Old 02-03-2014, 03:13 PM   #3
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One of the best and cheapest investments I every made in engine maintenance was the purchase of a hand-held IR temperature sensor. I bought mine at Lowe's for $40. With that you can pinpoint heating problems anywhere on the engine with typical accuracy of .01 degree Fahrenheit. Good luck!
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Old 02-03-2014, 04:05 PM   #4
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When you pulled the head did you clean the water passages in the head and block. After 35 years, old coolant, sitting, debris etc no telling why that part of the engine is overheating. Sometimes a failed or incorrect head gasket can block cooling passages.

Could your mechanic measure the crank bearing at that cylinder.? Are you sure you don't have seawater coming into number 6 due to a problem with the exhaust elbow or run?

Lots to conjecture about.
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Old 02-03-2014, 04:16 PM   #5
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We used a new head gasket when reassembling the engine. Mechanic checked various tolerances and nothing caught his attention.
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Old 02-03-2014, 05:10 PM   #6
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In what manner was the piston destroyed? Do you have the piston(s) and can you post photos of them?

Running that engine at 1400 shouldn't overheat a cylinder unless there is absolutely zero water flow or it was seriously overfueled. Either way, there should have been some exhaust smoke or a stink in the engine room.

You said the injectors were "checked" and were OK, were they just pop tested and did they go back in the same hole? Has the fuel pump been flow tested and calibrated to insure each injector receives the same amount of fuel?

I suspect there is more to the story.
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Old 02-03-2014, 05:22 PM   #7
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In what manner was the piston destroyed? Do you have the piston(s) and can you post photos of them?

Running that engine at 1400 shouldn't overheat a cylinder unless there is absolutely zero water flow or it was seriously overfueled. Either way, there should have been some exhaust smoke or a stink in the engine room.

You said the injectors were "checked" and were OK, were they just pop tested and did they go back in the same hole? Has the fuel pump been flow tested and calibrated to insure each injector receives the same amount of fuel?

I suspect there is more to the story.
OK maritime Paul Harvey....

But I think you are correct.

I remember but can't put my finger on any other stories...but I seem to remember someone or several people discussing the #6 cylinder on Lehmans and being cooling problems.

I too would love to see the piston..and it's very easy to get water damage in #6 the way many were installed...and with a second episode that soon I wonder.

Rick, what would water ingestion damage look like in the small, over time amount and then a rather large slurp?
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Old 02-03-2014, 05:39 PM   #8
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I hope this picture comes through.
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Old 02-03-2014, 05:48 PM   #9
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I'll try again to send the picture.
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Old 02-03-2014, 05:52 PM   #10
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I took the injectors to American Diesel and they tested them. Both the pop test and spray pattern were ok. Injectors did not go back In the same hole.
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Old 02-03-2014, 06:00 PM   #11
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I had some discussion with BS about an FL overheating. He raised the possibility of blockage at #6 and opening the bottom drain.
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Old 02-03-2014, 06:35 PM   #12
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So Paul Harvey whaduya think?
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Old 02-03-2014, 06:44 PM   #13
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Cylinder needs to be carefully checked with a bore gauge. Suspect something out of round. Need to check in multiple orientations and heights.
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Old 02-03-2014, 07:08 PM   #14
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I'll try again to send the picture.
Hmmmm, I wouldn't use that piston again if I were you.

Do you have a photo of the piston crown? From the looks of that piston, the siezure could have been through overheating at the rings (caused by a cooling failure or severe scuffing) or from a lubrication failure - was the pin in very bad shape and appear to have been siezing as well?

Are the crankshaft oil passages clear?

Lastly, it looks like what you would expect if the cylinder was heavily overloaded. Does the crown show indications of melting or erosion in a pattern similar to what the injector spray might make? The amount of carbon on the upper part of the piston is suspicious for such a short running time. This brings back the thought of fuel pump calibration.
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Old 02-03-2014, 08:01 PM   #15
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The number 6 is becoming more of a problem. The PO of my last boat just had the same problem, one of his 2 120s baked number 6. It can't be an issue with the marinizing as this is a water jacket or lubrication (or as Rick says, a fuel) issue.

Your mechanic pooched the repair if it only lasted 5 hours...
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Old 02-03-2014, 09:32 PM   #16
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The PO of my last boat just had the same problem, one of his 2 120s baked number 6. ...
XS

What was the problem and what was done to resolve the issue in your vessel's #6 hole?
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Old 02-03-2014, 10:03 PM   #17
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From another forum, after the engine was pulled apart: "Current conclusion is that it was definitely a case of overheating. He noted that many engines fail at the #6 cylinder as it is the furthest from the coolest water. They will also examine the internals of the exchangers and confirm flow through the seacock to check for blockage as a possible cause."

This fellow had all the pistons done, well, actually a total overhaul, damper plate etc. Compression was low in number 6 and lower than normal in number 3. He also did not report any apparent overheating while running, normal gauges. His failure occurred at wot, his piston looked exactly like yours.

Industrial Engines in New Westminster sells rebuilds. Probably get one at a tractor/farm dealership too, might be cheaper than an overhaul. Also, my friend's insurance co. paid for part of the repair as a premature failure. That might help.
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Old 02-03-2014, 10:03 PM   #18
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Dickhein,
Has the piston recently been installed in the #6 hole prior to your first failure? I'm thinking a ring could have been installed w too small of a gap and this could be made worse w an out of round bore.
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Old 02-04-2014, 07:47 AM   #19
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Another thought is that your cooling system has another problem that reduces the performance of your cooling system over-all. The #6 cyl being a weak link your engine runs hot and it shows up at the #6 cyl but you've said the engine wasn't hot. Perhaps your gauge wasn't telling you the truth. Something simpler like this is probably at fault and a combination of 2 problems is even more likely.
.
The temp sender for the FL 120 is on the front of the block #1 cyl, that is why #6 can overheat without the operator knowing.
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Old 02-04-2014, 08:04 AM   #20
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In what manner was the piston destroyed? Do you have the piston(s) and can you post photos of them?

Running that engine at 1400 shouldn't overheat a cylinder unless there is absolutely zero water flow or it was seriously overfueled. Either way, there should have been some exhaust smoke or a stink in the engine room.

You said the injectors were "checked" and were OK, were they just pop tested and did they go back in the same hole? Has the fuel pump been flow tested and calibrated to insure each injector receives the same amount of fuel?

I suspect there is more to the story.
I too agree. There must be more to the story and as i read the original post, I do not see where the mechanic solved the original problem. He seemed to just replace parts.
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