Checking Coolant Level

Coolant can be vented on track or leak away unnoticed, and the car has no gauge or reservoir that shows the level. So there is nothing to read: you top the radiator up and see how much it takes.

1. With the engine cool, release cooling system pressure by pulling the red tab up on radiator cap, then twist the cap off.
2. Add distilled water until no more goes in.
3. Twist the cap back on and ensure the red lever is aligned with the notch and all the way down.

How much it took is the useful number. A radiator that takes a lot when it should take a splash is telling you the coolant went somewhere. Note it each weekend and a slow loss shows up long before it strands you.

Fitting an expansion tank

The car leaves the factory without one, and that is why this page exists: with nothing to read, checking the level means opening the radiator every weekend.

An expansion tank gives the system somewhere to push coolant when it heats up, and somewhere to draw it back from as it cools. Two things follow. You get a level you can see without tools, and the radiator stops starting each session slightly down and full of air, which is the state that makes a marginal cooling system overheat.

Owners who have fitted one generally did it after chasing exactly that: repeated top-ups, air in the system, and temperatures that crept up over a weekend. It is worth considering alongside a radiator repair rather than instead of one, since a tank manages the symptom of a leak without fixing the leak.

Expansion tanks are permitted under section 19.4.5 of the 2026 technical regulations.

After an overheat

If the water temperature climbed and then would not come back down, even at a reduced pace, assume coolant was vented until you can prove otherwise.

1. Let the car cool before opening anything. The system is pressurized and hot coolant will come out at you.
2. Look for staining around the vent hole on the inboard side of the radiator fill port. Vented coolant leaves a mark there.
3. Top the radiator up as above, and keep rough track of how much water goes in. That number tells you how much you actually lost.
4. Burp the system. Any time you put coolant back in, air goes in with it, so burping is always worth doing rather than assuming the fill was enough.

Some overflow on the first heat cycle after a fill is normal rather than a leak. The cap bleeds at 22 psi.

If the car needs topping up repeatedly, or overheats again shortly after being topped up, stop treating it as a level problem. Air is being drawn in somewhere, and a pinhole in the radiator is the first place to look. See Pin hole leaks.