Lintu
Proven Member
- 40
- 38
- Oct 29, 2025
-
São Paulo,
South America
Hello guys!
Just wanted to share how I fixed the Low Coolant Level Sensor on my 1995 2G Eclipse GS-T.
Symptoms
- Car came with the Low Coolant Level Sensor unplugged
- Plugging it in would immediately trigger the Radiator Warning Light
- In practice, the sensor was non-functional
Preparation
- Remove the coolant expansion tank (disconnect the sensor if needed)
- Drain the tank
(I saved the coolant in a clean bottle and reused it afterward)
Removing the sensor
- The sensor is held in place by a rubber bushing
Carefully pull the sensor out using pliers
Do NOT squeeze the plastic body
- Since the rubber is ~30 years old, expect the bushing to fail
(mine did — more on that later)
- With the sensor removed, take the opportunity to clean the expansion tank thoroughly, inside and out.
How the sensor works
Despite the name, this “sensor” is really just a simple magnetic switch:
- A plastic cylindrical buoy slides up and down inside a hollow plastic shaft
- The buoy contains a magnet seated in a recess
Inside the shaft there is a normally-closed reed switch
- As the coolant level rises or falls, the buoy moves and the magnet opens/closes the reed switch
- A clear plastic cylindrical cover protects the assembly
- Two wires exit directly from the reed switch at the bottom
Simple and elegant.
Pre-test (before disassembly)
- Turn the sensor upside down and right side up. Make sure the buoy moves freely inside the shaft
- Check continuity across the two sensor wires:
Sensor upright > continuity
Sensor upside down > no continuity
Electrically, mine was fine — so I moved on to mechanical testing.
Sensor disassembly
The shaft tip is plastic-welded to the outer cylindrical cover
- Use an exacto knife to carefully break the plastic weld at the top
Leave enough material so it can be melted back later
- Slide the outer cover off
You’ll now see the buoy — note its orientation
(It can be installed both ways, but behaves differently. Magnet side goes UP.)
Floating test
- Drop the buoy into a glass of water
- It should float
Mine didn’t
Fixing the buoy
- I punched a small ring out of anti-static pink foam (electronics packaging foam). It has air trapped inside, so it should help with flotation.
Outer diameter = buoy outer diameter
Inner hole = buoy inner diameter
- Pressed the foam ring into the magnet recess of the buoy
- Re-tested in water → the buoy now floats
Functional test
- Temporarily reassemble the sensor
- Place it in a glass of water
As the water level rises:
- Buoy moves up
- Continuity across the wires changes accordingly
Sensor fully functional again.
Final reassembly
- Reinstall the buoy and plastic cover
- Melt the tip of the plastic shaft back into the cover to lock it in place
Since the original rubber bushing failed, I:
- Sealed the sensor to the expansion tank using black high-temp engine silicone
- Let cure for 24 hours
- Reinstall the tank and reconnect the sensor
Result
- Warning light behaves correctly
- Sensor works as intended
- No leaks
That’s it — hope this helps someone dealing with the same issue!
Just wanted to share how I fixed the Low Coolant Level Sensor on my 1995 2G Eclipse GS-T.
Symptoms
- Car came with the Low Coolant Level Sensor unplugged
- Plugging it in would immediately trigger the Radiator Warning Light
- In practice, the sensor was non-functional
Preparation
- Remove the coolant expansion tank (disconnect the sensor if needed)
- Drain the tank
(I saved the coolant in a clean bottle and reused it afterward)
Removing the sensor
You must be logged in to view this image or video.
You must be logged in to view this image or video.
- The sensor is held in place by a rubber bushing
Carefully pull the sensor out using pliers
Do NOT squeeze the plastic body- Since the rubber is ~30 years old, expect the bushing to fail
(mine did — more on that later)
You must be logged in to view this image or video.
- With the sensor removed, take the opportunity to clean the expansion tank thoroughly, inside and out.
How the sensor works
You must be logged in to view this image or video.
Despite the name, this “sensor” is really just a simple magnetic switch:
- A plastic cylindrical buoy slides up and down inside a hollow plastic shaft
- The buoy contains a magnet seated in a recess
Inside the shaft there is a normally-closed reed switch
You must be logged in to view this image or video.
You must be logged in to view this image or video.
- As the coolant level rises or falls, the buoy moves and the magnet opens/closes the reed switch
- A clear plastic cylindrical cover protects the assembly
- Two wires exit directly from the reed switch at the bottom
Simple and elegant.
Pre-test (before disassembly)
- Turn the sensor upside down and right side up. Make sure the buoy moves freely inside the shaft
- Check continuity across the two sensor wires:
Sensor upright > continuity
Sensor upside down > no continuity
Electrically, mine was fine — so I moved on to mechanical testing.
Sensor disassembly
The shaft tip is plastic-welded to the outer cylindrical cover
- Use an exacto knife to carefully break the plastic weld at the top
Leave enough material so it can be melted back later- Slide the outer cover off
You’ll now see the buoy — note its orientation
(It can be installed both ways, but behaves differently. Magnet side goes UP.)
Floating test
- Drop the buoy into a glass of water
- It should float
Mine didn’t
Fixing the buoy
- I punched a small ring out of anti-static pink foam (electronics packaging foam). It has air trapped inside, so it should help with flotation.
Outer diameter = buoy outer diameter
Inner hole = buoy inner diameter
- Pressed the foam ring into the magnet recess of the buoy
You must be logged in to view this image or video.
- Re-tested in water → the buoy now floats
Functional test
- Temporarily reassemble the sensor
- Place it in a glass of water
As the water level rises:
- Buoy moves up
- Continuity across the wires changes accordingly
Sensor fully functional again.
You must be logged in to view this image or video.
Final reassembly
- Reinstall the buoy and plastic cover
- Melt the tip of the plastic shaft back into the cover to lock it in place
Since the original rubber bushing failed, I:
- Sealed the sensor to the expansion tank using black high-temp engine silicone
- Let cure for 24 hours
You must be logged in to view this image or video.
- Reinstall the tank and reconnect the sensor
You must be logged in to view this image or video.
Result
- Warning light behaves correctly
- Sensor works as intended
- No leaks
That’s it — hope this helps someone dealing with the same issue!
