Union officials pleaded with supporters to remain disciplined outside the headquarters in Braamfontein of the Congress of SA Trade Unions (Congress) but said after an hour they would need to disperse.
Marshalls for the National Union of Metalworkers of SA (Numsa) manned the entrances to the park near the building, where they had gathered.
Supporters, many in black Numsa T-shirts, sang songs criticising Cosatu president Sidumo Dlamini.
“Sidumo Dlamini has no manners and does not respect older people,” they sang in Xhosa.
The metalworkers’ union has to give the CEC reasons why it should not be expelled, or suspended, after being accused of contravening the trade union federation’s constitution.
The CEC had apparently spent most of the morning debating credentials.
It was deciding whether Cosatu second deputy president Zingiswa Losi should remain in the meeting.
Losi resigned from Ford earlier this year, where she was a shop steward for Numsa.
This called into question her eligibility to continue to serve as a Cosatu leader.
Following her resignation she joined the Police and Prisons Civil Rights Union.
She was suspended by her local Numsa branch in Port Elizabeth in the Eastern Cape last year.
Meanwhile, red Numsa posters were fixed onto the fence surrounding the park.
“Reclaim Cosatu for workers unity”, “Defend Numsa! Defeat factionalism!” read some of the posters.
Earlier, Numsa president Andrew Chirwa told supporters the union’s leadership would be “slaughtered” during the meeting, but it would fight.
The High Court in Johannesburg on Thursday postponed an application to stop the CEC from meeting on Friday.