Fluctuating coolant reservoir levels

[AllanS]

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?

 

[Strecker25]

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?

a quart is quite a bit but the fact they both went down at the same time is curious and would make me less concerned. Any indication of coolant burning out the exhaust? It would be white smoke and smell a little sweet.

how about when you filled, we’re the expansion tanks completely full? It’s possible you had some headspace or air in the system and the overflow bottles had some sucked back in when the engines cooled.

I’d continue to run the boat and monitor as you’ve been, I doubt you have any issues.

 

[dtfeld]

Did the temperature go down significantly at the end of the trip?

 

[my3sons]

Or did you sit for a few days? 1600 pounds of iron don’t really cool off over night, keeping that coolant expanded.