Originally Posted by PaulM
- I found the freshwater coolant level low and the overflow reservoir (2 L bottle) half full of coolant.
- I removed the thermostat in case it was bad (it was fully open on removal), replaced the coolant and tried again.
- The system pressurized and pushed the coolant to the reservoir.
The only things I can think of that would cause this are, a bad head gasket, a broken freshwater pump or a major blockage to circulation. I did not notice any diesel contamination or odor
in coolant, but I not sure I would. Am I missing something else? All insight is appreciated
Freshwater coolant low and overflow tank half full.
The freshwater system should overflow to the puke tank if the pressure is too high. Low raw coolant flow is one reason the fresh water can overpressure. Head gasket failure (extremely rare unless an overtemp has occurred) can also do it but there could be side effecs such as bubbles in the fresh system and perhaps oil in coolant or vice versa.
After a puke event there should be a suction line that allows the fresh coolant to be drawn back into the fresh system as the pressure drops.
To find the fresh system low and the puke tank not full sounds strange.
It is also possible that you are not getting the fresh system full to start with.
-Reinstall the thermostat
-Fill the raw system - leave the heat exchanger cap off
start the engine - monitor
the fresh tank, once the collant reaches thermostat temperature and the thermostat opens the coolant should start circulating and the fluid level will drop
-Once the coolant start circulating continue to fill the fresh system until the coolant is flowing properly and the coolant system is full - the system could appear full but have an air lock in the block until the system starts circulating
- Fill the puke tank to the witness line or if no line about 1/3-1/2 full.
- Concurrently - with the engine running make sure the raw water
system is flowing
"the system pressurized and pushed coolant into the reservoir"
-Can you validate this? Was it a little coolant? How much coolant was "pushed." There is a lot of coolant in the system if it is actually getting pushed into the puke tank the puke tank should be overflowing into the bilge
- if the coolant is really escaping via the puke tank the puke tank won't hold the volume of the coolant.
The only other scenario is the coolant is going into the oil - not likely as you would surely notice this and also the oil pressure is higher than the coolant temperature except after shut down and it is more likely for oil to be in the coolant.
One theory for this is that there is an airlock in the block. The air heats rapidly, presurizes the fresh system and blows the exchanger cap seal.
- Check the air lock scenario and check the heat exchanger cap seal and seating surface as well
(edit - PS - If your puke tank has no line fill to 1/3 cold and mark it. If you note the level at normal operating temperature and it is higher, mark that as well - then you will know where you are in the future. Lowering of the cold temp over time means you are vaporing off some coolant and will need to add some perdiodically. Too much is not good)