As many of you know, these cars did not come with a coolant level sensor from the factory. This is unfortunate because the cooling system is a well-known weak point – coolant hoses and fittings turn brittle and crack with age, sometimes resulting in a small leak, other times causing catastrophic coolant loss. This post will give a brief overview of an aftermarket solution to this tremendous oversight.
I don’t want to take any chances with my car, so I bought an aftermarket coolant expansion tank with a built-in level sensor. When installed, the sensor is wired-in line with the coolant temp sensor so that if the expansion tank were to drain, the car would think it’s overheating and immediately issue a visible warning to the dash. Here’s a link to the expansion tank I bought on eBay. You can also purchase one from Swedish car parts here. I paid $200 for mine when I bought it ~6 months ago, but it looks like the price was increased to $240.
Quick look at the new tank, you can see the added sensor:
Before installation, I wired up the new expansion tank and gave it a quick test run. When the tank is empty, the car immediately issues a warning to the dash, and the temp gauge quickly climbs the max:
Installation is straightforward, at least on my 2.4i. I won’t cover installing the new expansion tank, because the process no different that the factory unit. Here’s a great video that I followed. With the new tank in place, I routed the cable underneath the upper intake manifold, and zip tied it to an existing wiring harness:
Then, connect the level sensor in line with the coolant temp sensor. With the unwieldy stock airbox in the way, disconnecting the harness from the temp sensor is a pain. I ended up using a flat head screwdriver to push in the tab on the connector. With a bit of luck, it stayed pushed in allowing me to gently tug at the harness and disconnect the sensor. The aftermarket coolant level sensor has two connectors – plug one into the coolant level sensor, and the other into the harness.
I tried to get a picture of the level sensor connected in-line with the temp sensor. There’s not a lot of room to work with on the 2.4i with stock airbox, but you can just make out the grey connector from the expansion tank sensor that plugs into the car’s wiring harness. I then bundled up the excess cable, leaving enough slack that the engine can move around without stressing the cable.
After six months of driving with the new expansion tank and sensor installed, I haven’t run into a single issue with it. To me, the piece of mind of having the sensor is well worth the cost. If I experience any coolant loss, I’ll get an immediately warning allowing me to quickly pull over and assess the situation – guess we’ll wait and see if that ever happens!