Heat Exchanger Coolant Loss
Posted: 13 May 2023
We often get told by owners that they find
headertank water levels low when they do routine checks before going out, and
despite then filling up, they again find the level low again the next day.
This is quite normal, as when the water in the engine heats up in running, it expands more than the metal of the engine components does and so excess water is forced out of the overflow pipe and lost, and so when the engine cools down again and coolant contracts, air is sucked in to replace it
Lancing Marine offer a specific header tank expansion tank kit. Please select the link or see the links at the bottom of this page, including for spare parts such as O-rings. We recomend this 0.75L tank as its designed for the task.
To always keep the headertank coolant at a good working level a set-up is needed to recover and re-use the expelled. A simple set-up would be something like this:
a length of hose that is a good push fit onto the headertank overflow
connection and run it down through the lid of a bottle or other
container that will take 1-2 litres (a Coke bottle will do for
- Ensure the hose reaches the close to the bottom of the
container.The container may be above or below the headertank, position
in a convient location.
- Approximately fill the container one quarter
full with water.
the heat exchanger cap rubber seals. Ensure that both seal rubbers of
the cap (one on the end of the spring and one in the cap that you grasp
to remove it) are in good condition.
- Top up the Heat Exchanger tank.
the engine is hot observe the amount of coolant in the container and
have another look when the engine has cooled right down.
not remove the filler cap in this time! If you are happy that the
system works, tidy it up with a nice, well secured container and
carefully positioned hose. ..
IF IN DOUBT, ASK LANCING MARINE FOR HELP
Click on an image for a larger view.