120 Diesel Lehman Over heating

[C lectric]

I've posted three tomes that I sometimes offer to save a lot of typing, mine.

Read them through and where questions arise, ask.
---First covers filling the coolant system and the use of a recovery system.
---Second covers many causes of overheating and what to look for
---THird is Ski in NC's advice for testing for a leaking head gasket.

THe second post of your links showed the water level overflowing but this will happen if you fill to the cap mounting neck. When filling you should leave at least about 2" low to allow for coolant expansion AND burping of air pockets.

Specifically did you fill the exchanger to the cap neck?

 

[Moonfish]

Had a similar sounding problem last year with my port FL120. I was getting pressurized overflow at the cap, and thought it was a bleed issue. After a few drains/refills, my friend and I realized the heat exchanger had failed and seawater was coming into the coolant system accounting for the increased pressure and quantity. At that point it was a "DUH!" moment...

Removed/replaced the heat exchanger and voila! Everything was fine again.

 

[omoore]

I had exact same problem. Everything checked out but still overheated. Turned out tang on pump drive shaft had sheared

FYI, you can get the engine up to temp by running it in gear at 1200-1300 rpm. Add lines and fenders if need be. I do this all the time.
You can buy a kit that will detect the fumes from a bad head gasket.
Good luck!

 

[ramkay]

I think it's only over filled. Temp is normal

 

[READY]

I think early posts indicated it reached 220 and shut down. I may have missed but how is the flow out the exhausts? Is it cool, warm or hot?

 

[brianaderer]

Hi Tom
Having just gone through this with a FL120 I may be able to add a few things here. As was mentioned before, call Brian at American Diesel. He is THE expert on these engines, and all the info I'm repeating and parts I'm referencing came from him. AFAIK the bubbling is normal. Here are some things to think about:

1) There is a breather passage in the front of the expansion tank that tends to get clogged over time. There's no real way to unclog it. The solution is to install an overflow catch reservoir and a new filler neck. Here is a picture of the new filler neck ready for epoxy in.
https://photos.app.goo.gl/TtvFnrbHbAca8HZy5
The hose goes to a catch bottle and forms a system that basically circumvents the blocked overflow passage. As the engine heats up, natural expansion of the coolant causes it to overflow out. The idea behind this system is that a tube goes on that nipple to a low mounted catch tank, and it just forms a siphon so that any expelled excess is just sucked back in when the engine cools off again.
2) Others have mentioned bleeding it. That's a good idea also. The bleeder valve is located on the port side of the engine just aft of the expansion tank. It's that little petcock you can see in your video. With the engine running, open it a bit until you can feel fluid/air coming out, wait for a steady stream, then close it and then top the system off at the expansion tank.
3) 120 is very cool for these engines. You want 165-180 IIRC, measured at the #6 cylinder (all the way fore) on the block with an accurate IR gun. Frequently the gauges are not correct - mine wasn't - so while you are at it it's worth it to verify. Running cool is bad also, Brian says that the cylinders don't take their shape until they reach operating temperature, so it's important to run it gently until it reaches full operating temp. It's not like the old detroits where you just turn the key and bury the throttle.

Hope this helps some. I definitely recommend a call to Brian (not me) @ American Diesel in Virginia. Guaranteed you will learn something. Good luck!

Brian

May I ask all of you experienced and knowledgeable folks to take a look at my video of my motor running and the Coolant reservoir "Burping" and comment if this is "Normal"
And if it isn't I'd, sure be grateful for any constructive comments and suggestions as to where I can find the culprit......

Thanks

Tom McBride
Long Beach
Shoreline Marina.


https://drive.google.com/drive/folders/1FRLH4lPt2l-U2LKLyUI27h_mAYHtEXci?usp=sharing

 

[brianaderer]

btw, I ended up, with Brian's help, as running too cool. Turns out there was no thermostat in there.

 

[psneeld]

You are NOT supposed to open the bleed petcock on the manifold from what I have read and been told. Doesnt make a lot of sense to me but that is rhe "guidance" that it may suck air in. Like many things I thing there are "maybes" that no one source discusses well.

Not all bubbling in the expansion tank is normal.

Thought #6 cylinder was aft.

Take all Lehman advice with the idea of quadruple checking it, even past American Diesel.

 

[captjohn7]

Head gasket

I just had to replace 2 head gaskets. Yours is cooked. Stop overheating the motor.

 

[ronobrien]

Tom Foolery sounds right. That is my first thought. You can buy a cheap borescope attachment for an I-phone. Pull the injectors and look inside the cylinders. That should tell you something.

 

[ronobrien]

On second thought, you would need to clarify "burping".

 

[captjohn7]

What ?

Pulling the injectors and looking with a boroscope ? That has NOTHING to do with the head gasket. I have never read a thread with so much bad advice. Sorry ,your head gasket is gone. Call Brian at American Diesel and order the gasket set.

 

[GB3295]

FL 120 overheating

This last bit changes it up a bit. If it overheats away from dock shut down, you can always restart to dock.
Other things can be raw water impeller, heat exchanger, hoses, thru hull. Still not seeing the head gasket looking at video.

Dear All,

I had the same overflowing into the pan below the engine on my 1968 GB 32. It has happened twice. What could be the reason, as I do not see a direct answer to that paragraph in the original post. I am.not an engineer, but would really like to learn more about my engine, it has been serviced by a local marine engine firm here in Seattle. No issues, temp runs around the 200 degrees, but after a longer cruise, I twice found quite an amount of coolant in the basin below the engine. It worries me as my GB 33 has only one engine and the Puget Sound is pretty big when you break down.......

 

[rgano]

Tom, do yourself and your engines a favor and call American Diesel and order the coolant recovery tank modification kit. One of the best things I ever did for my FL 120s. Why all the guessing about a head gasket problem when this https://tinyurl.com/3vanvcch is available for 24 bucks to test it?

 

[brianaderer]

You are NOT supposed to open the bleed petcock on the manifold from what I have read and been told. Doesnt make a lot of sense to me but that is rhe "guidance" that it may suck air in. Like many things I thing there are "maybes" that no one source discusses well.

Not all bubbling in the expansion tank is normal.

Thought #6 cylinder was aft.

Take all Lehman advice with the idea of quadruple checking it, even past American Diesel.

Brian at AD was the one who said to bleed it there. Seems pretty obvious, otherwise you'd have a bubble hanging out there, right? Where did you hear this, and why? I may have my cylinder #'s switched, but I definitely know that the one you are supposed to temp is all the way on the fore side, I thought that was #6 but maybe not. Read point is on the fore face of the block, just below where the expansion tank meets the engine.

 

[OldDan1943]

May I suggest, if you attempt to bleed it there, attach a hose to the bleed point and immerse the other end i a container of fresh coolant, incase it does try to suck plus you can see when all the air bubbles exit.

 

[rgano]

You are NOT supposed to open the bleed petcock on the manifold from what I have read and been told. Doesn't make a lot of sense to me but that is the "guidance" that it may suck air in. Like many things I thing there are "maybes" that no one source discusses well.

Not all bubbling in the expansion tank is normal.

Thought #6 cylinder was aft.

Take all Lehman advice with the idea of quadruple checking it, even past American Diesel.

The FL 120 Owner's Manual specifically directs the opening of the bleed petcock when filling the system, but I would not open it while the engine is running - maybe that is what you are referring to. I cannot remember his detailed post at this second, but from everything he said that I CAN remember, I think he would have checked the seawater flow at the exhaust against the engine's twin. I maintain that at least checking for exhaust gases in the coolant is a logical step before moving forward.

 

[BruceK]

1) There is a breather passage in the front of the expansion tank that tends to get clogged over time. There's no real way to unclog it. The solution is to install an overflow catch reservoir and a new filler neck. Here is a picture of the new filler neck ready for epoxy in.
https://photos.app.goo.gl/TtvFnrbHbAca8HZy5
The hose goes to a catch bottle and forms a system that basically circumvents the blocked overflow passage. As the engine heats up, natural expansion of the coolant causes it to overflow out. The idea behind this system is that a tube goes on that nipple to a low mounted catch tank, and it just forms a siphon so that any expelled excess is just sucked back in when the engine cools off again.


Brian

The blocked tube can be drilled out.

 

[reeltime]

I think the same thing as Soo Valley,
Both my engines do the same with cap off ,,,and never overheat ,
The little cock on top of the heatexchanger may need bleeding ,,you do this with the engine OFF , keep filling header tank until all bubbles stop then close the cock and keep filling header tank , replace cap ant test run .
Cheers

 

[reeltime]

And yes the small tube to the expansion tank can block , easy to take off tube and right angle brass fitting and clean out compressed air or on a bad one I used a long series drill bit .
And change the cap ,if you have an expansion tank as when engine cools it sucks back from that tank

 

[Trawlerman]

I very much doubt that it is a head gasket problem, especially if you do not have any hydrolock problems. What I do think that I see is your heat exchanger gasket leaking so that the raw water cooling is getting into the antifreeze circuit. As such, if this is the case, it will never stop "burping". Your raw water pump is pumping sea water into the heat exchanger, and there is supposed to be a barrier between the sea water (raw water) and the water jacket water. I see almost no antifreeze color in what you are burping, so this tells me that something has thoroughly diluted the antifreeze, and it is likely "sea" water. This seems much more likely to me than head gasket. FWIW. Could very well be a leak in the tube stack, or a gasket. My engines are Perkins, so not exactly the same but very similar.

 

[SteveK]

On second thought, you would need to clarify "burping".

watch the video and you name what you see.

 

[Orest]

THAT has happened to me

Best investigation is to get a combustion leak tester from Amazon under $50.
It fits instead of your coolant overflow cap . Just follow the instructions and that is the definitive test to eliminate or confirm its the head gasket.
It might also be from the exhaust manifold which can be tested with a common pressure tester inserted into the bleeder valve on top of the exhaust manifold. It should hold pressure . This might be your first test.

but;
bubbling into the coolant is from combustion gases.

 

[Orest]

Tom , For testing your can use a pressure guage like from a compressor Screw it into the overflow plug on top of your exhaust manifold.
Run your engine with the "rad cap" on until it warms up and pressurises the coolant.
Shut off your engine and the pressure should not drop.

If the pressure drops your manifold has a leak and is possibly leaking into your engine.
If your pressure holds THEN YOUR EXHAUST MANIFOLD IS OK and its likely your head gasket .

 

[Orest]

One more thing .. A head gasket issue would smell up your boat like exhaust fumes

 

[catalinajack]

Many owners of Lehman 120s open the bleeding peacock before starting the engine as a matter of routine. Check engine and transmission oil, bleed air, check coolant level, start engine, every time.

The FL 120 Owner's Manual specifically directs the opening of the bleed petcock when filling the system, but I would not open it while the engine is running - maybe that is what you are referring to. I cannot remember his detailed post at this second, but from everything he said that I CAN remember, I think he would have checked the seawater flow at the exhaust against the engine's twin. I maintain that at least checking for exhaust gases in the coolant is a logical step before moving forward.

 

[catalinajack]

If that indeed is what is happening a simple fluid test would confirm that.

I very much doubt that it is a head gasket problem, especially if you do not have any hydrolock problems. What I do think that I see is your heat exchanger gasket leaking so that the raw water cooling is getting into the antifreeze circuit. As such, if this is the case, it will never stop "burping". Your raw water pump is pumping sea water into the heat exchanger, and there is supposed to be a barrier between the sea water (raw water) and the water jacket water. I see almost no antifreeze color in what you are burping, so this tells me that something has thoroughly diluted the antifreeze, and it is likely "sea" water. This seems much more likely to me than head gasket. FWIW. Could very well be a leak in the tube stack, or a gasket. My engines are Perkins, so not exactly the same but very similar.

 

[rgano]

Best investigation is to get a combustion leak tester from Amazon under $50.
It fits instead of your coolant overflow cap . Just follow the instructions and that is the definitive test to eliminate or confirm its the head gasket.
It might also be from the exhaust manifold which can be tested with a common pressure tester inserted into the bleeder valve on top of the exhaust manifold. It should hold pressure . This might be your first test.

but;
bubbling into the coolant is from combustion gases.

I quite agree, but Tom's problem with fitting the usual variety of testers to the reservoir cap is that he still has to old 4 PSI wide mouth filler neck for which he will have lots of fun trying to find an adapter. He really, really need to do the American Diesel filler neck mod which adds the exterior recovery bottle (aiding day-to-day monitoring of the engine's coolant usage) as well as the higher pressure cap which comes with it.

 

[psneeld]

Brian at AD was the one who said to bleed it there. Seems pretty obvious, otherwise you'd have a bubble hanging out there, right? Where did you hear this, and why? I may have my cylinder #'s switched, but I definitely know that the one you are supposed to temp is all the way on the fore side, I thought that was #6 but maybe not. Read point is on the fore face of the block, just below where the expansion tank meets the engine.

Here is a "list of fixes" by Bob Smith on "Everything about boats"

Ford & Lehman "Fixes" that need to be accomplished before the engine suffers damage:
(Click links below to go to special in-depth "Members Only" articles on each "Fix" + more)

Fix engine misfire before injection pump governor and internal engine damage results.
Fix fuel injection pump lubricant before injection pump & governor damage results.
Fix engine oil filter hoses and attachment before internal engine damage results.
Fix engine oil cooler before cooler fails and engine damage results.
Fix engine drive gears before gears fail and serious internal engine damage results.
Fix "Two Shaft" raw water pump before shaft fails and engine overheat damage results.
Fix Exhaust Elbow before engine overheating or hydrolocking results.
Flush water jacket around rear-most cylinder and fit rear coolant fitting.

And here is the petcock instructions from my manual.

 

[psneeld]

I quite agree, but Tom's problem with fitting the usual variety of testers to the reservoir cap is that he still has to old 4 PSI wide mouth filler neck for which he will have lots of fun trying to find an adapter. He really, really need to do the American Diesel filler neck mod which adds the exterior recovery bottle (aiding day-to-day monitoring of the engine's coolant usage) as well as the higher pressure cap which comes with it.

True.... although I think I have seen a rubber plug adapter that you just squeeze down. ( not sure I would trust my findings over a cap adapter).

This was a method a very experienced Leman mech used with me on my bubble stream in the coolant tank. As I described earlier, he let the pressure build as the engine got to temp ( he let it go about a 1/2 hour or so under light loading, bleeding off pressure as it built. He said the coolant should have reached a max pressure when the temp leveled out but the continuous pressure build signaled a tiny hairline crack or issue with my head gasket, allowing combustion gas into the coolant.

No my boat didn't smell, and no the combustion check kits using fluid color change didn't show positive either, but sure did when I exposed it to a cars exhaust. Yes the kit was for diesel.