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Hi folks, my late model Atomic 4 was experiencing an unrelated problem with a loose plug wire and low power under load, while trouble shooting this by running the engine under load I experienced an overheating situation. I thought a hose had burst but I believe the filler cap relieved pressure and sprayed coolant over the engine. I have a freshwater cooling system with a horizontal heat exchanger. There was a good flow of sea water out the exhaust at the time. The temperature was up to 195 on the guage, and likely hotter at the head. I have since repaired the plug wire and the engine is running well even under load now. The engine temperature however still seems to be high 190 -195 when at crusing speed and after refilling the coolant (50/50 water and antifreeze) and when hot coolant starts running out the overflow and around the cap spraying on the engine. I filled it while the engine was running just warm and filled it to the top. Did I place too much coolant in ? Also it appears that the engine is running much hotter than it should. Would my overheating event have caused a permanent problem for the cooling system and what it the proper coolant refilling procedure? Thanks Mike
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Coolant overflow/Overheating
Just an update on my overheating problem. I did install a 3/8" ball valve in the bypass line and ran the engine up to temperature at the dock, 1400 rpm in gear. With the valve open temperature increased to 190 on the instrument guage and 210 on a meat thermometer stuck between the head and the exhaust manifold. With the valve closed the temperature dropped to 175 on the guage, and about 190 on the thermometer (handy tool). My fill cap possibly wasn't on its tightest position before. therefore allowing release sooner. There was no problem this time. I also now have a hose and bottle to catch it saves antifreeze on a hot engine and to the bilge (using low toxic stuff). I then took the boat out of gear and reduced rpm to about 700 idle, after a while I noticed the temperature on the guage reduced to 140 with valve closed and increased to 160 with the valve open. I think at the end of the season I will look into removing the thermostat and checking out its operation or the boss it seats against. Meanwhile I will just adjust the valve to throttle for operation at crusing speed. I hope to try it out this afternoon under full load.
Is it worth while to flush and acid wash the cooling passages of a FWC engine or just the exhaust portion?
Thanks for the oportunity to talk about my concerns and help from related threads.
Mike -
Mike,
The temperatures you're reporting should in no way have created any major problems within your engine.
I can't be sure about yours, but most heat exchangers have a hose barb just under the fill cap with a hose connected to it which can be run to a plastic expansion tank (like the ones on most automobiles). If you don't have such a tank, you can pick up an expansion tank kit at most automotive parts stores.
If you have no hose barb under your cap, you should let approximately 1 inch of air space between the antifreeze level and the top of the exchanger. If the level is still a bit too high, you might get a small amount of antifreeze out from under the cap the next time you run the engine, but from then on there shouldn't be any more antifreeze coming out of the system.
If a continuous amount of antifreeze is forced out from under the cap we'll have to consider that compression may be leaking into the system from the engine, but it's probably premature to go down that road at this time.
DonComment
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Thanks Don,
I do have a 1/4" hose barb from the fill cap nozzel and I have installed a vented plastic bottle attached to to collect any coolant overflow. I think the cap wasn't at the proper seating position when it was leaking. Its not a problem now. I also have installed a ball valve in the bypass line which solves the heating problem. I ran today for 1/2 hour at 2000 rpm 5.6 knots against a moderate head wind and temperature while valve was closed, did not exceed 170 deg. F. I am also pleased to hear about the FWC not needing a flushing.
Regards MikeComment
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Mike,
It's usually only necessary to flush the sea water side of the system. You
can easily monitor the sea water side by observing the amount of water
flowing out of the exhaust system.
DonComment
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