It was initially believed that the motoring fanatic had died as a result of injuries sustained while working on a car at home in Saggart, Dublin.
But in a statement at the weekend, they revealed that their son had taken his own life.
The owners of l'Ecrivain restaurant also stated that it had not been their intention to "mislead", adding that they had hoped Andrew would recover and they had not wanted him "to be stigmatised by his actions in a moment of madness."
They said they made the decision to protect their only son after paramedics found a heartbeat in the ambulance.
On the Thursday after Christmas Sallyanne discovered her son lying "cold and unconscious" in their garage.
This weekend, the couple said in a statement they "prayed and hoped for a miracle".
"If he survived we didn't want him to be stigmatised by his actions in a moment of madness. We were also extremely concerned about the effect this would have on Andrew's cousins, close friends and fellow pupils."
"We issued a statement in response to press queries in which we did not comment on the nature of Andrew's death, but took the opportunity to pay tribute to him. It was not our intention to mislead."
The Clarkes, with daughter Sarah May (22), said they hope people will understand their reasons behind concealing the circumstances of Andrew's death.
"We know all parents will understand our plight and we'd like to thank everyone who has supported us through these dark days from the bottom of our hearts," they said.