Hi, just took a 10 day trip in our 1989 SeaRay 440 Aft Cabin with twin Caterpillar 3208 turbo engines (375 HP). Before our trip I topped off the coolant level in each engines reservoir to “Full, Cold”. Every morning when I routinely checked fluid levels and belt tensions the coolant reservoirs on both engines were at that same level (Full, Cold). On Day 9 this changed and both coolant levels were down about a quart, and remained so after Day 10. What would cause this to happen? Is this cause for concern?
Coolant level in reservoir
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tiltrider1
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Odd that both have experienced the same issue. I would top both expansion tanks back up and continue to monitor daily. There are many things that could cause one engine to be down a quart but only an handful of items that would cause both engines to be down at the same time. Do you heat water off of both engines? Were you running harder than normal on day 9?
guy with a boat
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Did the weather change? Colder temps will cause lower “Cold” levels. The volume of coolant in the engines is enough that the difference can be pretty noticable.
certainly something to be tracking down. the coolant has to be going somewhere.
funny that both engines are doing the same. if it were a failed device of some kind, it probably wouldn't be both at the same time. i guess it could happen, but it would be pretty rare.
did you run the engines harder than usual? maybe get the temps up a bit and send coolant out the overflows? block both raw intakes with eel grass or kelp causing higher temps maybe?
are there coolant recovery tanks, and do they work properly? i've seen the coolant pressure caps fail and not pull back the coolant from the recovery tanks.
i'd have a look at the recovery tanks just before shut down to see if they're totally full.
Greg QS
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Probally air in the system. Your topping off in the bottle, on you long run you probally got the system hot enough to expel into the coolant bottle ang burp out the air. Both engines did the same thing so its probally how you are filling them up. You should also make a habit of checking the HOT level. Did you simply expel fluid out of the coolant bottles when hot. It is most likely not a mechanical problem since is almost impossible for 2 engines to have a failure that will show up exactly the same way .
Many good suggestions, keep them coming. Let me add what I discovered at the boat today. On the starboard engine the level came back up a bit, so I think the changes in reservoir levels on that engine are just normal expansion and contraction, perhaps also filling some trapped air.
The port engine however, is a different story. I found a lot of coolant under the engine, sitting in the engine bilge, enough to account for the loss from the reservoir. This is the engine that serves the hot water heater, but I could see no evidence of leaks from those hoses or fittings. Also, the coolant in the engine bilge must have come from the engine, since the expansion reservoir is located outside this engine bilge, so the expansion tank did not leak it out. I removed the pressure cap from the metal reservoir on top of the engine, and could not feel any coolant with my fingers down to 4” or so.
With this new info, any ideas? Neither engine got hot during my trip, although we had some heavy seas one day. Is the spring loaded cap on the metal reservoir suspect?
The port engine however, is a different story. I found a lot of coolant under the engine, sitting in the engine bilge, enough to account for the loss from the reservoir. This is the engine that serves the hot water heater, but I could see no evidence of leaks from those hoses or fittings. Also, the coolant in the engine bilge must have come from the engine, since the expansion reservoir is located outside this engine bilge, so the expansion tank did not leak it out. I removed the pressure cap from the metal reservoir on top of the engine, and could not feel any coolant with my fingers down to 4” or so.
With this new info, any ideas? Neither engine got hot during my trip, although we had some heavy seas one day. Is the spring loaded cap on the metal reservoir suspect?
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The open air under the radiator cap and lack of coolant in the coolant bottle overflow area tells me you have a leak. If you are certain it is not in the lines going to the water heater, and since the coolant is under the engine, it is not leaking into the water heater through an internal leak there (hint: keep the freshwater system pressurized underway to make sure you never get coolant in the water heater). The next place I would check is the weep hole at the lower portion of the engine's circulating pump. A worn bearing there will allow a weep to start there. I found my own circ pump leaking when I noted a drop of coolant on the bottom off the crank shaft pulley after cool down - traced it back up. At least with the coolant found in the drip pan, the specter of a broken head gasket or cracked head does not have to be considered.
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Wrap a towel around the radiator cap. They can leak and hard to detect. Had the same problem. Wound up being a bad radiator cap. Was leaking out and sucking air back in. So the fluid was not going into the overflow bottle. Was one of my cheapest repairs yet.
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tiltrider1
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3208’s have heat exchangers on the front of the engine. There is a cap on the heat exchanger. If you look carefully there is a hose connected to the neck that the cap fits on. This hose runs down the engine and disappears. It doesn’t really disappear it just ends. If the coolant system over pressurizes the excess coolant is dumped into the bilge via this hose.
Most of the 3208’s coolant system is internal. There are only a few places that it can leak chEcking those few hose conNections is pretty easy. The other possibility is the auxiliary take off, in your case this is the water heater.
Most likely, day 9 was a hot day and the system became over pressurized dumping excess coolant in the bilge. This would explain why both engines had the same issue.
Most of the 3208’s coolant system is internal. There are only a few places that it can leak chEcking those few hose conNections is pretty easy. The other possibility is the auxiliary take off, in your case this is the water heater.
Most likely, day 9 was a hot day and the system became over pressurized dumping excess coolant in the bilge. This would explain why both engines had the same issue.
you're right about that, can be hard to detect. also, not sure how the caps mounting boss is attached to the header tank, but on some tanks you can develop a leak there that a new cap won't fix.
On my engines, the pressure cap is located on a metal tank next to (part of) the heat exchanger. Yes, it has a hose attached at the next, which I can trace to the plastic expansion reservoir, so coolant pressure in the engine SHOULD result in coolant returning to the plastic expansion reservoir. I should check on the integrity of that hose to be sure. Could a bad cap release coolant without it going into the recovery tube?
Where can one get the proper replacement cap? Worth a quick try. Any value in buying a radiator pressure tester to pressurize the system and look for leaks?
Where can one get the proper replacement cap? Worth a quick try. Any value in buying a radiator pressure tester to pressurize the system and look for leaks?
jleonard
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Make sure the hose that leads to the plastic reservoir is not plugged up.
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A common cause of a slow loss of coolant are pin holes in the heat exchanger. The closed cooling on the circulation pump is at a much higher pressure than the raw water on the raw water pump. This causes the coolant to leak into the raw water and get discharged out the exhaust. small pinholes from corrosion lead to slow leak times.
It would be unusual, but not impossible for both heat exchangers to start to expire around the same time if they are the same vintage, conditions, service, etc.
It would be unusual, but not impossible for both heat exchangers to start to expire around the same time if they are the same vintage, conditions, service, etc.
Very informative post. I have twin 3208s N/A 210 HP. I go through radiator caps like I go through underwear (I'm trying a vegan diet). I was also adding coolant (very small amount) at a regular interval. It took awhile to realize the level in the overflow tank, when cold, was extremely varied. It never emptied. I ended up putting a paper towel downhill of the cap, so I could detect the problem early on and replace the cap. Since doing this I havn't needed to refill the overflow tank. I also put the white diapers under each engine to assist with detecting leaks. I will be checking for the overflow tube from the heat exchanger. Didn't know that was a thing. Thanks.
TG
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Check for weeping or leaks at the End Caps of the Water Cooled Exhaust manifolds. The gaskets can develop leaks. Check the oil cooler, Engine Coolant circulates through that exchanger.
Owen Christensen
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Coolant leak
I had the same problem exactly. It started last season and this season noticed the color of coolant in the bilge. That was good news because then I knew it wasn’t the intercooler. It was the water pump for the engine, not the lake water impeller. As they get worn they leak through a weep hole and it is hard to detect. Mine are fixed now. I replaced them on both motors even though it seemed to be just one leaking.
Owen
I had the same problem exactly. It started last season and this season noticed the color of coolant in the bilge. That was good news because then I knew it wasn’t the intercooler. It was the water pump for the engine, not the lake water impeller. As they get worn they leak through a weep hole and it is hard to detect. Mine are fixed now. I replaced them on both motors even though it seemed to be just one leaking.
Owen
