Ford Lehman 120 Coolant Leak

[RonHurd]

Coolant in Lehman 120 is topped off and engine will run at normal temp. However, when the engine is shut down I lose almost all the fluid in the expansion tank to the overflow outlet/line.

This hasn't happened before and I am trying to determine what may be the cause of this recent issue. Any advice would be appreciated.

Thanks,

Ron Hurd
M/V Shangri La - 46' Cheoy Lee Trawler

 

[Westiculo]

Where does it end up? It just disappears? Or it shows up under the engine?

 

[psneeld]

If the tank is empty at the end of a cruise and not just dumping at shutdown.....


Start and run engine with cap off...look for bubbles in coolant. If none after a couple minutes increase RPMs to at least 1500 or near cruise RPM and look again.

If you really can't tell, borrow a pressure checker from an auto store. warm up engine with cap off and then secure pressure checker....look for pressure increase.... bleed off and recheck several times.

This is what an experienced mech did to mine and helped me confirm a tiny head gasket leak....also had a very, very TINY amount of oil or soot in coolant tank.

I was losing most of my coolant too. So to help diagnose, I installed the new cap modification and coolant tank kit from American Diesel. Made things easier and at least I wasn't losing the coolant to the bilge each time.

 

[RonHurd]

Overflow goes into a jug below the engine. The issue is: why is all the coolant being discharged in the overflow line after shutting down the engine.

Thanks,

 

[Cigatoo]

Are you referring to the plastic coolant recovery tank? That should be on the empty side when engine is cold. It will gradually fill as the engine warms and coolant expands. Reverse as engine cools.

 

[psneeld]

Are you referring to the plastic coolant recovery tank? That should be on the empty side when engine is cold. It will gradually fill as the engine warms and coolant expands. Reverse as engine cools.

I f one hasn't done the filler neck and cap modification, there is no "recovery tank" and sihoning back.

 

[Cigatoo]

Ok...No plastic bottle
“However, when the engine is shut down I lose almost all the fluid in the expansion tank to the overflow outlet/line.”

Try a new radiator cap. Probably a standard 13 lb automotive cap will work. Someone correct me if I am wrong on the pressure relieve.

 

[psneeld]

I am not positive but I think Lehman 120s have an 4 PSI cap standard...but is is not like standard caps as it is not designed for coolant recovery....not sure what the modded neck cap is...


https://www.fredwarner1.net/product...MIwP3b1pLz4AIVhx-GCh3QiAnjEAQYAiABEgIqRPD_BwE

 

[alormaria]

Don't put on a standard automotive radiator cap. It has way too high a pressure for the Lehman. You should be able to get the correct cap from American Diesel.

 

[C lectric]

Be aware of what PSNEELD described as it can cause this while an engine operates. However once the engine is shut off then compression leaks should be gone I expect so the pressure will dissipate and not push the coolant out.

Another cause could be when the engine is shut down some areas in the block, head and manifold cooling system may actually boil the coolant with out the circulation from the running engine. THat will raise pressure in the whole system forcing coolant out after shutdown. If this is going on then it may be time to clean and inspect the system for border line cooling capacity from fouling or wear in some areas.

It does sound like you have a recovery system. The fact that there is a hose from the filler neck to a bottle says it has been installed. It simply may not be working properly any longer.

Does or did the coolant pull back in as the engine cools down? Don't open the cap or the vacuum will be lost and the coolant will not pull back.

Did it used to fill the recovery bottle as the engine heated and then pull the coolant back in as the engine cooled down? If it did then the cap sounds like it is a proper coolant recovery type cap.

If it no longer pulls the coolant back upon cool down then the cap has failed and should be replaced.
I will point out this feature can fail for other reasons such as a dirty sealing area at the neck and the cap or a loose hose clamp or two somewhere in the coolant system which allows air in as the engine cools defeating the recovery function.

 

[Spinner]

I can’t speak to that exact engine, but I had a case of the disappearing coolant recently. It turned out to be a failing heater core (red dot heater). NOW I have shut-off valves for the coolant hoses that go to the (new) red dot heater and to the hot water tank...it might be worth checking....

 

[slowjoe]

Call Brian from AD if he don’t no nobody will

 

[BruceK]

I have Lehman experience,I`m no mechanic,and have Mercruiser overflow recovery bottles fitted.
From my motor sport days, it was not unusual for an engine to effectively boil if shut down suddenly after a high speed run. Idling the engines down might help.
Are your engines running hot in any event? That might exacerbate the process. Lehmans can develop blocking/silting at no.6 cylinder cooling passages, another potential exacerbation. Maybe take a look at what happens just after shut down.
The cap is 4psi, slightly higher if the ADC recovery kit is fitted.

 

[C lectric]

I have Lehman experience,I`m no mechanic,and have Mercruiser overflow recovery bottles fitted.
From my motor sport days, it was not unusual for an engine to effectively boil if shut down suddenly after a high speed run. Idling the engines down might help.
Are your engines running hot in any event? That might exacerbate the process. Lehmans can develop blocking/silting at no.6 cylinder cooling passages, another potential exacerbation. Maybe take a look at what happens just after shut down.
The cap is 4psi, slightly higher if the ADC recovery kit is fitted.

Better explanation than mine of the why the boil . Are you doing an abrupt shutdown after a run? I don't believe in a long cool down but I won't come in hard and then kill the engine. Usually though getting to a slip or finding the perfect anchoring spot is more than enough cool down time.

 

[Ardell]

Possible leak in Heat Exchanger

Hi, I recently had a problem where the coolant level was fine with the engine running, but would lose about a quart after the engine was shut down and cooled off. No coolant leak inside the boat, nor to the oil, etc.

Turned out to be a leak within the heat exchange. As boat cooled, raw water pressure went down, but coolant pressure still high. Forced fluid into the raw water side.

Good luck,

 

[Searunner37]

I just pulled my mixing elbow to check it and had to put a new gasket on and forgot to re-tighten after running the engine which ended up as coolant loss. In my case there was crystal buildup around the joint so it was pretty obvious. If you end up opening that joint Brian said to use Permatex on the manifold side of the gasket.
Bob Johnson
Guinness
KK 4241

 

[rgano]

I have not seen here where the coolant recovery bottle/expansion tank neck modification was completed. What Searunner 37 MAY have is an unmodified engine with the original overflow tube going into a bottle under the engine as many people have done. If the modification has been dome, the new coolant expansion tank neck is a piece of bronze, and rather than the single action 4 PSI cap in a photo earier in this thread, there is a new 7 PSI DOULBLE ACTING radiator cap (as supplied by Brian at American Diesel) in place which allows the fluid to be sucked back into the engine as the engine cools.

This seemingly sudden expulsion of the coolant after shutdown could be the result of several things, a faulty unmodified overflow, heat pockets in the engine after shutdown and a faulty old-style single acting radiator cap.

I would suggest getting the modification made and mounting th recovery bottle level with the expansion tank. As a minimum, change the radiator cap, whichever style it is.

Think about flushing the engine's coolant system with some motor flush.

Several decades of living with two of these wonderful engine speaking here.

 

[mlaloli]

I'm no mechanic either...

We had a similar issue with our lehman. Tuens out I had been over filling the header tank. There was no room in the header tank for it to expand and it was simply discharging into the overflow. Now I leave a much more generous gap and no longer have issues.

 

[rgano]

maloli, you describe exactly what happened to both my FL120s BEFORE I made the modofication to the filler necks on the expansion tank. After I made the fix, the expansion tanks were always maintained completely full, just like I find on my cars with odern, double-acting radiator caps. I highly recommend the mod!

 

[Searunner37]

I have not seen here where the coolant recovery bottle/expansion tank neck modification was completed. What Searunner 37 MAY have is an unmodified engine with the original overflow tube going into a bottle under the engine as many people have done. .

I might have confused the matter so here is a photo of my coolant recovery and one pointing to the gasket in question.
Bob

 

[Moonfish]

Ron, I really like your boat!

 

[rgano]

That looks like the neck has been modified, but the radiator cap does not look lik a double acting type - can't tell for sure.

 

[albinalaska]

I seem to be having a somewhat similar issue with my Coolant on my port engine (FL120). Slightly more concerning though as we are on the hard. While at the dock a month ago we noticed port coolant tank empty (do not have a plastic overflow system installed). Cap was really crusty- probably original- So we ordered the cap recommended on this forum thinking it was just from shutting down too quickly and not letting the engines idle down enough. (Do not have this issue in stbd tank FYI but the coolant reservoir appears to have been upgraded).

But we replaced the cap, vacuumed out the coolant from the bilge (literally all of the coolant), examined the engine for signs of where it might be leaking in case that was the issue but couldn’t find anything. With the new cap we thought the issue was resolved.

Flash forward:

We’re out on the hard doing winter work and on a check the port coolant tank is empty again and the coolant is in the bilge... well, outboard side of the inner port stringer...

Where would this all be leaking from if not the overflow tube? There is no observable evidence of coolant on the engine that we’ve been able to find. Any advice would be greatly appreciated!

 

[Comodave]

I seem to be having a somewhat similar issue with my Coolant on my port engine (FL120). Slightly more concerning though as we are on the hard. While at the dock a month ago we noticed port coolant tank empty (do not have a plastic overflow system installed). Cap was really crusty- probably original- So we ordered the cap recommended on this forum thinking it was just from shutting down too quickly and not letting the engines idle down enough. (Do not have this issue in stbd tank FYI but the coolant reservoir appears to have been upgraded).

But we replaced the cap, vacuumed out the coolant from the bilge (literally all of the coolant), examined the engine for signs of where it might be leaking in case that was the issue but couldn’t find anything. With the new cap we thought the issue was resolved.

Flash forward:

We’re out on the hard doing winter work and on a check the port coolant tank is empty again and the coolant is in the bilge... well, outboard side of the inner port stringer...

Where would this all be leaking from if not the overflow tube? There is no observable evidence of coolant on the engine that we’ve been able to find. Any advice would be greatly appreciated!

My starboard engine has leaked coolant out the last 2 winters. Have not been able to find the leak yet. However during the summer it doesn’t leak when we are using it. I put a dye in but that hasn’t been definitive.

 

[SoWhat]

port engine is usually connected to heat water heater. Most likely source of leaks. Local auto parts store will loan you a pressure test kit. Add some UV dye to the coolant before testing.

 

[Xsbank]

Without the coolant recovery tank, you will put coolant in the bilge. The Lehman's seek their own coolant level and it's at a much lower level than you would expect. Spend a bit of money and modernize your engine with the new kit from American Diesel and stop peering in your header tank fearfully! There is also a bleed screw which should be used according to the manual.

Also, your recovery tank should be slightly higher than the header tank.

If all your maintenance is up to date, when did you last change your coolant? If you are not testing it regularly with coolant test strips (Cat sells 'em) you need to flush and change it, 5 years is maximum for the best coolants if you don't have a coolant filter. Coolant filters replenish the additives so you might consider adding one?

 

[C lectric]

Man, my tomes are getting a workout lately. Saves a lot of typing.
Most points have been covered here somewhere.
This is about the use of the coolant recovery systems as this subject comes up so often.
THey do help but like all things they do need to be understood and set up properly.

If you have more questions, ask.

 

[Marco Flamingo]

water heater. Most likely source of leaks.

That's where I found mine. I was slowly loosing coolant. Local auto parts store had a pressure tester, but it didn't have a test cap that fit my Lehman.

I bought a 50' length of heater hose (cheap price per foot) and decided to replace all of the old stuff to the water heater and bus heater. The hose to the water heater was obviously original, and right at the inlet it had surface crazing under the hose clamps and back a few more inches. Turns out that when the system was under pressure (and hot), that area would "sweat." I couldn't find any visible indication that it actually dripped out, but if it did, it would have gone directly into the shaft alley where, because of the dripping shaft seal, the evidence would have been diluted and routinely pumped overboard.

The proper coolant level in my FL is deceptively low. There is probably 2 inches of air above it that could be filled. But if filled, the next check will show the level back down 2 inches again. I decided to be brave and just leave it there. I now have almost 100 hours on the engine without the need to add coolant. I still think I will make a little dip stick with a notch to show the static level. Easier than looking down in or sticking my finger in and guessing.

 

[rgano]

I will admit right here that it took me a few years of performing the coolant level "dance" with my two FL120s before I got smart and added the American Diesel coolant recovery bottle and double acting radiator cap filler neck kit. What a difference in the ability to actively monitor the coolant status during both operation and post operation of the engines. I urge anybody with an unmodified FL120 the make this most sensible of changes.

 

[albinalaska]

port engine is usually connected to heat water heater. Most likely source of leaks. Local auto parts store will loan you a pressure test kit. Add some UV dye to the coolant before testing.

As it turns out that is exactly what it was! We knew the water heater (an old ball of rust that we had always planned on removing from the day we bought the boat) was leaking but it was such a slow rate it was almost impossible to see the green coloration of the coolant. It looked just like water dripping out. But examining the tank and subsequently removing it made it very obvious it was the culprit.

Regarding recharging the coolant lines is there anything I need to do or to be aware of? I’ve heard there can’t be air in the lines but not sure if there is anything else I need to deal with to not have any issues down the line. We are out on the hard for at least another year but if something serious enough came along we could go through the effort of getting water to the intakes to start the engines if necessary.

As always; thanks!