The Massachusetts Institute of Technology is entering the second week of a crippling strike by 885 maintenance, custodial and dining hall workers.

Eighty-five members of local 185 of the Cooks and Pastry Cooks Association rejected an MIT contract offer and went on strike Wednesday, joining 800 members of local 254 of the Service Employees International Union (SEIU) who had stopped working last Thursday.

The strikes have forced MIT to close all but one of its dining halls and stop all mail pickup and delivery, outgoing shipping and custodial and cleaning services.

MIT and SEIU officials yesterday held their first federally-mediated negotiating session since the strike began, but failed to reach a settlement.

An MIT statement said yesterday that the SEIU asked for a two-year contract with 10 per cent pay raises in each year. MIT has been offering the maintenance and custodial workers a two-year contract with 7.5 per cent raises.

Edward T. Sullivan, chairman of SEIU local 254, would neither confirm nor deny yesterday that the union asked for 10 per cent raises.

Sullivan said he expects the SEIU strike to end within three weeks.

The MIT statement said MIT "does not intend to add to the value" of its pay raise offer to the SEIU workers, but since the offer includes 3 per cent raises in pensions and other benefits, MIT could conceivably meet the union's pay demands while cutting back its benefit offer.

Sullivan charged MIT with refusing to bargain in good faith before the strike by presenting the union with a single nonnegotiable offer.

The cooks' union refused a contract similar to the one the SEIU rejected, but 49 MIT security guards yesterday accepted a near-identical contract.

Harvard employs 550 members of the cooks' union, but their contract--which had a no-strike clause in it--does not expire until June 1975. None of Harvard's employees are members of the SEIU.

Hundreds of striking workers have picketed in front of MIT buildings all week.

John M. Wynne, MIT's vice president for administration and personnel, said in a memorandum last week that MIT will "continue to carry on all activities that can be conducted safely" during the strike.

MIT last week set up an "emergency closing" telephone number that gives round-the-clock recorded information on the strike.

Last night's emergency message gave an account of the security guards' contract decision and went on to say, "The strike is still in progress. The Institute is open, and classes are being held all week. All employees are expected to report to work as usual."