Loss of coolant out the cap. What next?

[DustinM]

I made a large goof this past weekend by not adequately tightening down my Perkins T6.354.4 diesel's coolant cap after checking the coolant level before the cruise. About 2 hours into the trip, I noticed a whistling sound come from the engine, looked back to the exhaust and saw some white smoke coming out. I cut that engine off and went down to the engine room to find a big mess of splattered, sweet smelling coolant all over the engine, with lots of coolant steaming in the air. The drip pan below the engine was also filled with coolant (not certain the volume the pan can hold, but it's a few gallons at least. The engine holds about 5.5 gallons of coolant total.)

I made it back to the dock on my other engine. I took temperature readings with my infrared gun of the heat exchanger maybe 10-15 minutes following shutdown and found temps of approximately 195-200 degrees, though admittedly did not check everywhere and could have missed a hotter spot.

I haven't been able to find any threads of someone doing anything similar (running an engine with significantly reduced levels of coolant). Mostly threads of slow coolant leaks or people asking about running with no raw water cooling. I'm at a bit of a loss on what to check for and have not tried to start the engine since. Would love any suggestions or things to look for? I'm certainly not above calling a mechanic but do enjoy investigating things myself a bit, so long as it's not reckless. I have seen that head gaskets are a common failure point for an overheated engine, and also that coolant can leak into cylinders and hydro-lock an engine.

Thank you in advance!

 

[Comodave]

I am not a mechanic but I would probably fill it with coolant and see if it would run.

 

[RT Firefly]

Greetings,
Mr. D. What I would do is clean up my mess, fill the engine with coolant as per recommendations (Perkins manual) and bar it over. IF you can rotate the engine freely, try to start it.

 

[SteveK]

Greetings,
Mr. D. What I would do is clean up my mess, fill the engine with coolant as per recommendations (Perkins manual) and bar it over. IF you can rotate the engine freely, try to start it.

reverse order. Bar over first and if that goes well fill with coolant and turn the key.
You stopped the engine, it did not stop itself is a good sign.

 

[O C Diver]

I think you have more issues than a radiator cap not being tight. Generally white smoke / steam can be a sign of low raw water flow, as the exhaust is vaporizing the raw water.

Did the radiator cap come completely off?

Did the engine temperature gauge read over 200 degrees when you shut the engine down?

IMO, I think your engine overheated, forcing coolant out of the radiator cap. As mentioned by others, barring the engine over would be a good idea. I would consider pressure testing the coolant loop before filling it. I'm concerned that you might have a head gasket issue as well. If the coolant loop holds pressure, fill the loop and start the engine. Check the exhaust for raw water flow. Low or no flow is a sign of a raw water issue.

Ted

 

[KnotYet]

In addition to the suggestions above, after refilling the coolant and a test run to operating
temperature, examine the engine oil for any traces of coolant.

 

[DustinM]

Thank you for all of the recommendations. Ted was correct, it was a raw water cooling issue that just happened to pop up on the first day in a while that I’d been checking out the coolant cap. I hate coincidences. I think I may have even installed the cap tightly (I’ve noticed that the cap will back off about 1/8 of a turn after the engine’s been run as compared to the fully snug fit I tighten it down to).

I barred the engine over (was fine), refilled with coolant, turned it on and the engine ran fine, however, there was no water coming out the exhaust at all. My RW pump’s shaft was spinning, the impeller was in good condition, but there was no conversion of the shaft’s spinning into impeller spinning. I removed the pump to find that the pump’s splines had completely sheared off! I’ve since replaced the Jabsco pump with an Ancor pump and used the boat a few times since and all seems to be well. Thank you again for all of the help.

Anyone have any idea if this is a replaceable piece to the pump? The pump is only like 3 years old, I’d love to repair it if I could.

 

[O C Diver]

Thank you for all of the recommendations. Ted was correct, it was a raw water cooling issue that just happened to pop up on the first day in a while that I’d been checking out the coolant cap. I hate coincidences. I think I may have even installed the cap tightly (I’ve noticed that the cap will back off about 1/8 of a turn after the engine’s been run as compared to the fully snug fit I tighten it down to).

I barred the engine over (was fine), refilled with coolant, turned it on and the engine ran fine, however, there was no water coming out the exhaust at all. My RW pump’s shaft was spinning, the impeller was in good condition, but there was no conversion of the shaft’s spinning into impeller spinning. I removed the pump to find that the pump’s splines had completely sheared off! I’ve since replaced the Jabsco pump with an Ancor pump and used the boat a few times since and all seems to be well. Thank you again for all of the help.

Anyone have any idea if this is a replaceable piece to the pump? The pump is only like 3 years old, I’d love to repair it if I could.

Yes the shaft is replaceable. Not going to be cheap. Check the bearings and seals before buying the shaft.

I would contact Jabsco about the pump. The shaft should be hardened. They may see the wisdom in giving you a new shaft as opposed to having it featured on the internet. My Onan dealer was able to make that happen for me when the end of the shaft snapped off.

Ted

 

[rgano]

You definitely have a problem with your engine's coolant overheat alarm because without the seawater cooling, the coolant would soon be running over the threshold temperature for that alarm to go off. I have been saved a couple of times by audio/visual alarms.

I have experienced two overheated engines, one, a Ford-Lehman 120 HP and the other my current Yanmar 315 HP. The Lehman OH was minor when one of the coolant hoses on the engine partially failed. The engine did not immediately signal trouble because the coolant lose was slow leading to a very slow temperature buildup. The coolant over-heat alarm was making a low volume tinkling sound as the engine slowly heated. The person conning the boat called my attention to it, and I checked the gauges and then shut the engine down stbd engine due to the temp gauge reading high. As soon as the engine was off, the alarm came on full volume. After a quick hose change and some added coolant, we were on our way again.

The Yanmar casualty was a bit more like yours in that the seawater cooling flow suddenly stopped, but in this case, it was a burst exit hose from a fully functioning pump rather than a sheared pump shaft. That pump at the 3400 RPM I was running puts out 35 gallons a minute, and it's a tossup as to whether the bilge pump or the overheat alarm came on first because both audible and visual alarms were on when I looked down. I saved the engine by hitting the shutdown switch before even throttling down, but it burped and groaned for five minutes in a most ominous way.

I agree with Ted that the white "smoke" you saw may well have PRIMARILY been the seawater in the exhaust system (muffler included) boiling, but the coolant bubbling out of either the radiator cap and/or the coolant recovery bottle (you do have one, don't you?) and getting slung all over the place could also have been contributing to what you saw by being sucked into the engine's intake and run through the engine.

My advice after overheating is to change coolant and oil and get an oil analysis done on the old oil.

My other advice applies to the engine instrumentation needed to provide some peace of mind and accurate and immediate casualty

diagnosis in the future. I always install unique lighted idiot lights for bilge pumps, coolant overheat, low oil pressure, and water in the fuel filters for each engine in my boats so that when that single warning horn or bell goes off, I can immediately look down to see what parameter is in alarm mode. The two images illustrate my efforts on the single engine and the twin engine boats.

 

[Nepidae]

A suggestion that may help in the future is to put an overflow bottle on the system.

I have twin Ford Lehman's 135 engines and added a coolant overflow bottle to my engines.

As you can see, the bottles are squarish and hang from the front of the engine antifreeze (AF) container where the pressure cap is.

There is a small hose that attaches to a pipette under the pressure cap and goes to the overflow bottle.

What this enables me to do is to check the coolant level when I do other engine checks without removing the pressure cap from the engines.

You mentioned that your pressure cap comes loose so you may want to address that as well by picking up (2) new ones for the engine(s). Check your manual for what pressure you need.

It is reassuring to know that my AF levels are working as I see from my bottles that the level of coolant rises and falls based on the engine use.

 

[rgano]

EXCELLENT point, Charles. Radiator caps get old and tired and need to be replaced from time to time.

I too added recovery bottles to my circa 1972 FL120s, but that involved installation of a kit from American Diesel which included a new narrower filler neck because the original cap was of a very much larger diameter than anything available on the market today. The instruction which came with the kit included taking a chisel to the aluminum expansion tank to chip away the lip under the old cap and using something like MarineTex to glue in the new filler neck. It was a bit daunting to me at the time but worked out excellently for both engines.

 

[SteveK]

My current boat came with new rad caps which leaked requiring adding coolant after every run. Now correct caps years have gone by without loss of fluid.
Those new caps were the right pressure, not the right fit. Expansion of fluid should go into a reservoir and return to the engine as it cools, no where else.