Brooks Ayers Threatened To 'Tell-All' About Vicki Gunvalson During Nasty Split -- Left 'Furious' After She Canceled Their AmEx Credit Card!

The split between Vicki Gunvalson and Brooks Ayers got so ugly that her ex-lover threatened to go public with information he believed would damage her reputation, RadarOnline.com has been told.

The on-again, off-again pair split -- via text message -- in March when the Real Housewives of Orange County star, 51, finally decided enough was enough and put an end to their troubled romance.

But Brooks, who who began dating Vicki in 2011 in the wake of her divorce from ex-husband Don, was left "furious" after he never got an explanation for his spectacular dumping.

What's more, Vicki secretly canceled their shared American Express card, without telling him!

"Vicki dumped him via a text message," a source revealed.

"He was furious. Brooks told her that if she said anything negative about him in the media, he wasn't going to hold back. He was adamant that he would take her down. He said in no uncertain terms, 'Be very careful Vicki.'"

Brooks, who previously fought off claims he was a deadbeat dad, didn't take the split easily: He inundated Vicki with calls and text messages, said the insider, but the Bravo reality star simply ignored his advances.

At one point, she courageously barked at him, "Lose my number!"

"Brooks repeatedly would call and text Vicki and try and reconcile," the source said.

"It dragged on and on. At one point, he was in Las Vegas, with his children, when he discovered that Vicki had cancelled their shared credit card. Brooks was p*ssed. He felt that she purposefully embarrassed him in front of his children."

Speaking to RadarOnline.com in July, Vicki confirmed the split, declaring her "love tank was empty" after a tumultuous few months during which Brooks was accused of cheating on her with various porn stars.