Losing coolant on Ford Lehman

[CameronVP]

Hey forum, we have ford lehman with osco marinized heat exchanger on our boat. The problem we are having is that we are consistently losing coolant, to the point that we have to pour about half a gallon in every time we fire her up. Also, if we hit heavy seas, nearly all of it splashes out and begins to overheat. When we check, it is nearly empty. We have checked the cap, and have run a compression test. Both seem ok. Any thoughts? Much appreciated.

[tkeithlu]

By "comporession test" did you mean of the coolant system or of the cylinders? The most obvious leak (which you would not see) is between the coolant and the cooling raw water in the heat exchanger. A compression test based on compressed air through the coolant cap would demonstrate that.

If the coolant system holds pressure, then I'm inclined toward a small leak that is temperature dependent, or that it is getting into your exhaust through a bad gasket or (pray not) a crack.

If it stays a mystery the clue is where it is going, as for example catching the raw cooling water in a bucket and seeing if antifreeze comes to the top. Ditto for exhaust water if you have a wet exhaust, and steam out the stack if dry.

[CameronVP]

Thanks for the reply. By compression test, I meant on the coolant system. Also, there is no coolant in the raw water out into the ocean. Also important, we can definitely see coolant in the bilge. What do you suggest we do first? Checking gaskets first?

[Sailmonkey]

How does your coolant “splash” out in heavy seas? Are you missing a cap on something?

[CameronVP]

We dont see it visibly splashing out, but it definitely leaks much, much faster when healed over (were a sailboat) or in heavy seas.

[Shrew]

If the coolant isn't in the bilge, then the most common is through pin holes in the heat exchanger. The closed cooling side is much higher pressure than the raw water side. Coolant seeps from the closed cooling side into the raw water and is discharged out the exhaust into the ocean.

Coolant loss through healing and 'splashing' seems a bit weird.

[CameronVP]

Hi Shrew - The coolant definitely is in the bilge, and not coming out into the ocean.

[OldGreyB]

Originally Posted by CameronVP

Thanks for the reply. By compression test, I meant on the coolant system. Also, there is no coolant in the raw water out into the ocean. Also important, we can definitely see coolant in the bilge. What do you suggest we do first? Checking gaskets first?

You state you are losing up to half a gallon per run of the engine, that is a serious amount of water. I would be really worried if I was losing half a pint! I would strongly recommend you do not run this engine for long periods of time until you find the issue. Otherwise you potentially will overheat the engine to the stage where you will be in for big dollar repairs such as head gaskets or worse.

The leak should be obvious if you are losing that much water, and since you are seeing the coolant in the bilge, then this should be a relatively easy leak to find. You state you have pressure tested the coolant side and "all seems OK", but since you are losing coolant and seeing it in the bilge then the imperial evidence is that the coolant system is not water tight and it is definitely not OK.

The stated greater loss while healing or heavy seas is strange, but could indicate a loose clamp that the heavy sea motion is working this clamp loose.

Obtain the Leaman service manual if you have one and religiously follow the drawing, check every hose clamp and hose. Tighten each as you go. If a clamp or hose seems dubious, replace with a new one. Check all stud nuts on the heat exchanger are tight against the engine block. Even if you do not have a manual, cooling systems hoses are simple to follow. Also check where the coolant water circulation pump is, make sure that the coolant is not coming out via a worn seal on the pump shaft. If it is, you will see traces of water leakage on the engine block below the water pump.

Once you have done that you should have found the leak site and have fixed it. Clean and dry the bilge so you have no old coolant showing. Now fill the coolant system up and run the motor for say 10 minutes until up to temperature. Shut down and investigate if you have solved the issue. If you still see coolant in the bilge, wait unit the system is cooled sufficiently to refill, sprinkle white talcum powder on each and every joint and run the motor again until up to temperature. Shut down and check each location to see where the leak is showing on the talcum power.

Post back your resultants

[01kiwijohn]

Go to an auto parts store, with a tool loaner program, and get a cooling system pressure tester. Fill it up, pressurize it to about 10% over the specified pressure and leave it for at least 15 minutes. There should be NO loss of pressure. If no leaks externally visible, check the heat exchanger.

[Cheechako]

Is it possible you are overfilling when cold and it burps out via the pressure cap when warm into the bilge? Do you have a capture tank off the pressure cap tube?

or
Is it overheating, bad thermostat?.... and burping it out into the bilge?

[tkeithlu]

To chase down a leak, wipe down the engine with rags or paper towels. Then place towels under everywhere you think it may be leaking. Run briefly. Check the towels. when you find that one is wet, trace the leak upward from the spot.

I actually had to tie towels around the flare connections in my steering to find small leaks. In your case, it should be obvious.

OldGrayB, that's "empirical," as in evidence. I do it all the time. Unfortunately, the forum doesn't have spell check to blame it on.

[wrwakefield]

We have a Lehman SP90 from 1983. It has a (not so obvious) Y on the front of the engine- just below and inboard of the alternator. The Y allows a choice for plumbing the coolant loop. Only one of the two ends of the Y is used. The other is plugged with an 1-5/8” diameter freeze plug. Sometimes that freeze plug slowly leaks, and I have had them eject completely- dumping lots of antifreeze into the bilge and causing the engine to overheat. Lesson learned: don’t use any sealant when installing a new plug in the cooling system. Install them dry...

If this isn’t a contributing factor for your issue, call Brian at American Diesel ((804) 435-3107) for excellent expertise and best pricing and availability on parts.

There is also a Ford Lehman group on FB that seems to have some experienced and knowledgeable members.

Good luck resolving things.

Cheers! Bill

[captjohn7]

I was losing massive amounts of coolant and then motor would over heat. I needed to replace the head gasket. Engine exhaust would over pressurize the coolant system and force the coolant ont the expansion tank overflow. Just fill your system and fire it up and watch it . You will see where the coolant is coming from.

[OldGreyB]

Originally Posted by tkeithlu

OldGrayB, that's "empirical," as in evidence. I do it all the time. Unfortunately, the forum doesn't have spell check to blame it on.

Hello Tkeithlu. Yes I noticed my typo post the "time out" period for edits. The upside of you catching it is I now know atleast one person read my long post to the OP

[sailon46]

She my motor yanmar 100 turbo started doing that in a crossing from Guadeloupe to curaçao started leaking coolant In the bilge with a lot of searching I ended upfinding it under the turbo to a freeze plug that was deteriorating
Ernie on the Loremar