船到江心补漏迟（船到江心補漏遲）　

◎ 船到江心补漏迟 chuán dào jiāngxīn bǔ lòu chí

[It’s too late to plug the leak when the boat is in midstream] 船已经行驶到江中才补漏就太晚了,比喻对问题不及早解决,到时候就来不及了