Hyundai IX35 Pricing and Specs

What you need to do is work backwards and check every connection and wiring plug that is anywhere near where you were working. A single unplugged (or even loose) sensor, connection or fitting can absolutely sideline a modern, electronically controlled engine.

You may also find you’ve damaged a sensor in the process of cleaning it (they’re pretty sensitive things) so a scan of the car may reveal that.

Also, was the cleaning process initiated by an existing problem that made you think the sensors needed cleaning? Cleaning an already dud sensor rarely brings it back to life.

If the engine is not getting hot and the temperature gauge is reading normal, it’s difficult to see how the coolant could be boiling. Perhaps what you’re seeing is the coolant in the overflow bottle bubbling, which can appear as though it’s boiling. But the reality might be that you have a leaking cylinder head gasket.

When that happens, gasses from the combustion process can escape into the engine’s coolant system and appear as bubbles in the overflow system. And to the observer, that can look very much like boiling coolant.

Either way, you need to find a good workshop that can check this stuff and figure out what’s really going on. Only then can you diagnose the root problem and tackle it.

A poor earth is often the cause of this sort of misbehaviour and it’s a good place to start looking. Check the earthing points in the engine bay and around the area where the tail-lights are earthed in the cargo area.

You might need to lift some carpet or trim pieces, but when you find the earth points, make sure they’re tight and clean and not covered in corrosion. Don’t forget to check the tightness and cleanliness of the battery terminals, too.

Beyond that, these symptoms point to a problem with the car’s body computer which controls all these functions and many more.

When this computer starts to die, all sorts of weird and random flaws can occur. But try this first: Disconnect the battery of the car and let it sit overnight. Reconnect it next morning and keep a close eye on what happens. Sometimes this simple trick will reboot the body computer and normal service will be resumed. Best of all it’s free.