In the middle of the night almost 23 years ago, John Lang fled from police into bush scrub in Sydney's north. He's been missing ever since, and police today renewed an appeal for information about the former postman from Kenthurst.

At the time of his disappearance, Mr Lang, 25, police had been questioning him about stolen cars in the Windsor area.

He and a friend had been stopped by police in May 1985 near bushland at Putty Road, Colo Heights. The pair had been in a utility loaded with suspect vehicle parts, which Lang allegedly said had been innocently scavenged from wrecks dumped along a trail, the Sun Herald reported in 2006.

Mr Lang agreed, at 3.30am, to show police where the wrecks were.

As they drove along the bush track, Mr Lang flung open the passenger door of the police car and fled. He was pursued by police, but the chase was abandoned when one of the officers fell and injured his knee.

Friends and family have not heard from Mr Lang in the last 23 years. Police have monitored his bank accounts, but there has been no activity, said North West Metropolitan Region Commander Denis Clifford.

"One possiblility is that he's gone and changed his name and identity and is maybe still alive under that assumed identity," assistant commissioner Clifford said.

"But, although stealing a motor vehicle is a serious offence, it's not the most serious offence. [Changing your identity and cutting off contact with family] would be a very drastic thing to do for stealing motor vehicles."

Assistant commissioner Clifford believed Mr Lang  "accidentally met his fate in the bushland around Colo Heights".

"I think the man perished either on that night in the bush, or he wandered in the bush, got lost and [died a few days later]."

There have been numerous quests to find Mr Lang or his remains, the latest spurred by evidence presented at a coronial inquest into his disappearance that is currently in progress at Westmead Coroner's Court.

"During the inquest a female witness made a claim that if police were looking for Mr Lang they might find his remains at [what was previously Mr Lang's home]," assistant commissioner Clifford said.

Police yesterday searched the property, a large acreage in Kenthurst, but found nothing, he said.

A search in Colo Heights and of Mr Lang's Kenthurst home just days after he went missing also failed to locate anything. In October 2006, a 30-strong team of police officers and police rescue and cadaver dogs again combed the bushland. No evidence was found, police said.

Little else was known about Mr Lang. Assistant commissioner Clifford did not believe he had a serious criminal record.

Both his parents were dead, and he had a brother and a sister. The family have thus far declined to speak with the media, assistant commissioner Clifford said

The police officers who arrested Mr Lang had retired, but had given evidence at the inquest, he said.

Police asked the public for any information, no matter how insignificant, that could help them locate Mr Lang. They also appealed for Mr Lang to come forward.

Anyone with information can call Crime Stoppers on 1800 333 000. Callers can remain anonymous.