The bus that was ferrying the children and (right) the cap that came off the coolant tank, injuring four boys. Pictures by Pradip Sanyal

Four students going to school in a pool bus were scalded when the cap came off the coolant tank behind the driver’s seat and the hot liquid spouted out on Tuesday.

One of the children, a Class VI student, sustained burns on one of his hands and had to be admitted to hospital. The others suffered minor injuries and were discharged.

A preliminary examination of the bus — a 30-seater registered with the Howrah motor vehicles department — that ferries students of Shree Jain Vidyalaya suggested that the cap of the coolant tank had come off accidentally.

The accident illustrates once again how buses ferrying students flout rules. Buses ferrying schoolchildren cannot make them sit in the driver’s cabin. Police are also checking whether the bus had a contract carriage permit required to ferry schoolchildren.

“The metal lid of the coolant tank behind the driver’s seat faces the passenger seat in the driver’s cabin where the children were sitting. The coolant tank is connected to the radiator with a pipe. The coolant got overheated and spouted out of the container. A mechanical examination of the vehicle will ascertain whether the hot liquid had forced open the lid or the lid had come off by itself,” said a senior police officer.

The coolant, a composition of liquid chemicals, is circulated through the radiator to keep the engine cool. In the process, the coolant itself becomes hot.

The temperature of the coolant can rise to over 120 degrees Celsius. “The liquid can burst out like a fountain either because of a damaged engine or cracks in the hosepipe that carries the coolant,” an expert said.

“Bus passengers often sit on the radiator — concealed under an elevated metallic platform between the driver’s seat and seats for passengers on the left. Often the metal is very hot. That is because the coolant dissipates the heat of the engine to other parts,” the expert said.

The driver of the bus and his help were arrested on charges of negligence and rash driving.

The bus was speeding down the Brabourne Road flyover when the accident happened. “The four students were shifted to Calcutta Medical College and Hospital in a taxi,” said an officer of Burrabazar police station.

The student who received the maximum injuries was identified as Rishabh Tiwari, a resident of Upendra Nath Mitra Lane at Salkia in Howrah. “Two of our teachers immediately went to the hospital,” said a teacher of Shree Jain Vidyalaya on Sukeas Street.

Hospital sources told Metro that Rishabh had received “18 per cent burn injuries” and was released on Tuesday evening after his family signed a risk bond.

Car thieves held

Two persons were arrested on Monday in Kharagpur, where they were driving a car allegedly stolen from Girish Park. Police said Mohammad Shabir and Biswajit Khara had stolen a sports utility vehicle on September 21 and were on their way to Odisha when they were nabbed in Kharagpur.

The duo were allegedly involved in a car theft racket and had earlier stolen eight cars, all of which were taken to Odisha or Nepal.