Maryland Special Prosecutor Gerald Glass met yesterday with a Montgomery County grand jury that is investigating allegations of irregularities in the management of the county police department.

The grand jury apparently pursuing the inquiry on its own without the sanction of the state's attorney's office, has requested that its term be extended. The jury is scheduled to disband Sept. 28.

It could not be determined yesterday if Glass was conferring with the grand jurors about their inquiry into the police department or about their request to extend their term.

One focus of the panel's investigation is a set of allegations that Montgomery County Police Chief Robert J. diGrazia has in a variety of ways violated the department's established administrative procedures.

These allegations originally were made by a group called Code 3, which is headed by the wife of a county police officer and which for months has been vociferously critical of diGrazia's efforts to introduce new training and personnel procedures into the department.

The foreman of the county grand jury has written diGrazia a letter informing him that the panel was looking into these allegations by Margaret Jacocks, the head of Code 3 - a group whose name derives from the police radio call signal meaning "Serious Crime in Progress."

Under Maryland law, a grand jury - an investigatory body made up of 23 citzens - is impowered - both to issue indictments against persons suspected of crimes and to investigate and make reports on local government agencies.

Ordinarily, a grand jury is impaneled for a term of six months, after which it is disbanded and a new grand jury chosen.

According to Montgomery County Circuit Court Judge Richard Latham, grand jury foreman Arthur E. Johnson wrote a letter to State's Attorney Andrew Sonner at least 10 days ago asking to have the panel's term extended.

In order to extend the term. Sonner would have to file a formal petition with Latham - something he had not yet done, according to court records.

Yesterday, outside the grand jury meeting room, Glass refused to comment whether he plans to do anything about the jury's request for an extension. He has the authority to petition the court for an extension on behalf of the jury, Sonner said.

It is not clear why the grand jury started looking into the allegations made by Mrs. Jacock, but, according to sources familiar with the investigation, the panel has seemed determine to conduct its inquiry on its own, instead of working under the guidance of an assistant state's attorney, as is usual.

On one occasion, the panel asked both the prosecutor and the court stenographer to leave the grand jury room while it questioned a police officer, according to Cpl. Jerry Boone, who was waiting outside the grand jury room when one of his fellow officers testified.

Mrs. Jaycocks and other members of Code 3 have, over the past several months, tried unsuccessfully to interest both U.S. and county officials in an investigation of diGrazia's administration of the county police department.

Mrs. Jaycocks has charged that diGrazia violated certain procedures for awarding nonbid contracts to outside consultants, and that the contracts were awarded because diGrazia knew the consultants who had done work for him when he headed the Boston city police department.

To date, Code 3's allegations have been examined by the federal Law Enforcement Assistant Administration (LEAA) - which supplied some funds for consultans' studies of current police operations - and by the county's chief administrative officer, the FBI, the county's auditing department and a county council staff member.

LEAA officials, however, determined no LEAA funds were involved in the allegations, and the county auditing department, after examining the police department's 56-page response refuting the Code 3 allegations, issued a statement that, "police department response to the Code 3 allegations adequately answers the charges . . ."

DiGrazia has maintained throughout that Jacock and a "minority" of officers are attempting to sabotage him because of their disagreement with his policies.