Lehman 120 running temp

I thought my Lehman 120 overheated today. It always sits at 162 degrees while underway or idling. Comes up to temp and stays there. Today after changing fuel filters and running it afterwards the temp jumped to 190. I immediately shut it off. My manual says it should run 175 to 190 but 195 is optimum. I'm questioning my guage a bit now. What temp are other Lehman's running?

My 225s run about 185.

I have dual Lehman 2715E engines in my MT (120 HP). 190 is nothing. Typical diesels like a little heat. You are fine. Mine run at 130 at idle. 150 at running speed. But 190 does not hurt them. You should investigate why it is running hotter that normal though. But no, most likely you did them no harm.

Mine run 175-190. What is 195 is optimum mean? It seems preferred, then why not say 175-195.

I have a 185 degree thermostat installed. This Lehman 120 ALWAYS runs at 185 after warm up. I have a carat mark on my gauge at 185. If it runs any hotter than that there is a bad reason why.

I agree why not say 175 to 195? But it doesn't. I took a pic of the page.

And yes I did look and yes my expansion tank was empty. It has never changed in the 14 months I've owned the boat. The only thing ive done was change the zinc a week ago. Which is half today. So something is not normal or right. And if course I'm in Georgetown Exuma doing our self quarantine. No parts normally, and definitely no parts at the moment.

So, the expansion tank is empty. So, the question I have is how much coolant is actually left in the engine? You could start by adding water and keeping track of how much was added. The tank itself holds, what, two quarts at most, probably less. If it takes say two gallons then you know that your coolant is going bye bye and the next step is to determine where. How old is your heat exchanger? You are going to get a lot of speculation. My advice is to start simple.

Selidster said:

And yes I did look and yes my expansion tank was empty. It has never changed in the 14 months I've owned the boat. The only thing ive done was change the zinc a week ago. Which is half today. So something is not normal or right. And if course I'm in Georgetown Exuma doing our self quarantine. No parts normally, and definitely no parts at the moment.

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Could temps alter with changing fuel filters? Perhaps unrelated.
The important thing is, something changed, you need to investigate. 190 is in range, but it was 162, it`s now 190,a 17% increase. Even if it`s gauage(check with a heat gun), you need to know why.

The whole idea of the cooling system is to keep the engine at a constant economical running temp. A engine suffers excess wear if run to cold, (why we install thermostats) and suffer damage if to hot. The purpose of the thermostat is to warm the engine asap and maintain it at a efficient / low wear operating temp. One shold not operate a engine sans thermostat. Thermostats are not made exact, there are variances in manufacture. My Lehmans ran in the 180-195 range, depending on sea water temp etc.

First thing I looked at after the expansion tank was the oil. Its oil. Not a oil/coolant milkshake. Thank goodness.

already suggested, add measured water. Then run it and if it drops again, change heat exchanger, or have rad shop check it.
Can change of fuel filter change increase temp, I think perhaps if fuel flow is increased internal temp increases, then without enough coolant it overheats.
I am going to say 162 probably represents a gauge not reading accurately, so a ~30 increase could be like 210. Infrared heat gun temp sensor?

Yep going through it tomorrow with a fine tooth comb. Already postponed our travel plan till I have an understanding of what happened. I have a temp gun so I'll check the accuracy of the guage. I'll also check the thermostat and heat exchanger. Lot to do to sort it.

My single FL 120 runs 185 constantly going up 1 to 2 degrees when the 150 amp alternator is running at 100 amps.

Only time it went higher was when the heat exchanger clogged up on the raw side.

My starboard engine does something strange with coolant. After the winter last year I found about 2 to 3 gallons of coolant in the drip pan under the engine. I filled the engine with coolant. Again this winter I have a lot of coolant under the engine in the drip pan. The engine would not keep coolant in the overflow bottle ever since we bought the boat 4 years ago. I would keep adding coolant to the overflow bottle and it would keep going somewhere? But the level in the expansion tank would only drop to a certain level and then stay there. So I quit adding coolant and it never dropped below the certain level in the expansion tank. But then last winter I had the coolant in the drip pan and again this year the same thing. Last spring I added coolant when I launched and watched it all summer and had no more loss until this winter... Any ideas? SP225s.

Dave, I had the same thing, no loss of water then loss of water. Pinhole in the heat exchanger. After reflection on operation it seemed each time WOT was involved with water loss. Except for the pinhole the rest is speculation

If it was the heat exchanger then wouldn’t the coolant go out the exhaust? Mine is dropping into the drip pan under the engine sometime over the winter.

Comodave said:

If it was the heat exchanger then wouldn’t the coolant go out the exhaust? Mine is dropping into the drip pan under the engine sometime over the winter.

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I repeat this is a WAG as the only idea I can see that made sense for me.
You see the water which also suggest overheat so could be different cause.
impeller, raw water flow, circulation. Oh and the fresh water pump could be leaking.

I have 182deg. thermostats in my Lehmans. Temp gauge says 182-185 when running. Had coolant loss after sitting one winter and overheated on way to the haulout. Used pressure pump and gauge with blue towels around hoses and fittings. Found a small leak at hose connection. Tightened hose clamp which corrected problem. I now check my coolant levels when returning to the boat every May.

Tator

We put a pressure pump on it and didn’t find any leaks. I put a dye in it last year. Haven’t had a chance to use the black light on it yet.

Comodave said:

We put a pressure pump on it and didn’t find any leaks. I put a dye in it last year. Haven’t had a chance to use the black light on it yet.

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Oops, just remembered, I also replaced both rad caps. Only 4lbs.
The pressure pump reminded me.

Soo-Valley said:

Oops, just remembered, I also replaced both rad caps. Only 4lbs.
The pressure pump reminded me.

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Thanks, I have to put the black light on it and see if it shows anything.

That rules out a head gasket failure, an unlikely event but possible. More likely, the coolant is going out the exhaust through the heat exchanger. I just a few days ago replaced my 12-year-old exchangers on my FL 120s. I had no evidence of failure and, yes, I suppose they could have lasted years longer. I chose the CuproNickel version which is about $150 more. Cost was $703 each including shipping. Based on this thread, I am glad I spent the money.

While I was at it, I eliminated that hokey connection from the header tank to the exchanger that employs two steel tubes and two short hose connections (and clamps). Instead, I used a coupling at the short elbow from the header tank and then a single long run to the exchager using silicone radiator hose. I was very happy with the result.

Selidster said:

First thing I looked at after the expansion tank was the oil. Its oil. Not a oil/coolant milkshake. Thank goodness.

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Greetings,
Mr. c. "That rules out a head gasket failure..." Not necessarily. Might be a failure to the outside of the engine rather than the inside. Coolant leaks to drip pan instead of oil pan. Sorry. response to post #15.

I did say unlikely but possible. I also said in my first response to start simple. Wouldn't a coolant loss through a head gasket externally be easy to discern? How about draining the heat exchanger and then pressurize the coolant system with a radiator cap tool? If the exchanger were compromised, would it not then fill with coolant?

RT Firefly said:

Greetings,
Mr. c. "That rules out a head gasket failure..." Not necessarily. Might be a failure to the outside of the engine rather than the inside. Coolant leaks to drip pan instead of oil pan. Sorry. response to post #15.

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Mine runs at a bit over 180, just what the thermostat calls for.

I overheated mine rather severely one time. Following an injection pump replacement which caused an air lock in the system. I was driving from above and saw the temp gauge peg, looked down and saw steam billowing out of both side doors. Made a quick course correction and shut it down. Coasted into the well at my marina after calling for docking help, thinking I might need "braking" help.

Anyway, long story short. No damage

pete

Greetings,
Mr. 99. I fully agree. Start with the simplest things first. As you mention, a head gasket failure IS unlikely.


Regarding the potential external leak of coolant: Evidence of leakage might be discernible BUT it may be so slow, over time (as in winter storage) as to become almost invisible, source-wise.


At one point, our boat was in the Hinkley yard in Thunderbolt, GA. I had a pesky oil leak I just could not find the source of. Our Lehman IS oily to a small extent so the "trail" was invisible to me. Their mechanic at the time, Bob, spotted the source immediately. One small O-ring later and WALLA! Thanks Bob.

catalinajack said:

I did say unlikely but possible. I also said in my first response to start simple. Wouldn't a coolant loss through a head gasket externally be easy to discern? How about draining the heat exchanger and then pressurize the coolant system with a radiator cap tool? If the exchanger were compromised, would it not then fill with coolant?

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I searched the local auto parts and rental stores for a pressure kit that would fit the Lehman 4# radiator cap. No luck. It was all Honda, Toyota, Dodge, etc. None of the adapters would fit the big Lehman cap. Anybody found a source for renting a pressure tester? My next thought is a rubber cork drilled to fit a schrader valve, but renting the real thing would give me more confidence in the results.

Mark

second rad cap?

M

Marco Flamingo said:

I searched the local auto parts and rental stores for a pressure kit that would fit the Lehman 4# radiator cap. No luck. It was all Honda, Toyota, Dodge, etc. None of the adapters would fit the big Lehman cap. Anybody found a source for renting a pressure tester? My next thought is a rubber cork drilled to fit a schrader valve, but renting the real thing would give me more confidence in the results.

Mark

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Mytivac MV4560 test kit. Available on Amazon and Ebay. Has adapters to fit most systems. Can't imagine that it won't fit a Lehman cap which is quite ordinary on older American cars.