The DS3 RRC driver slid wide and branches pierced the radiator, causing a rise in the engine temperature.
Kubica and co-driver Maciek Baran carried out repairs between stages two and three, and are continuing in the rally.
But there were engine warnings in the cockpit of the car at the end of SS2, so there are fears that damage has already been done.
Unfortunately for Kubica, there is no service until the end of the leg on Friday.
He will now repeat the morning's two tests before embarking on a 250-mile round trip to Lisbon for the evening superspecial.
Kubica is running fourth in WRC2, 22.5 seconds off leader Esapekka Lappi.