In Cantonese, 車 has two pronunciations: [ce1] and [geoi1].
In Mandarin, 車 also has two different pinyin: [che1] and [ju1].
[ce1] corresponds to [che1].
[geoi1] corresponds to [ju1].
In most idioms, 車 is pronounced as [geoi1] in Cantonese. For example: 閉門造車, 車水馬龍, 前車可鑒, 螳臂擋車, 學富五車 and 舟車勞頓. All have the character 車 pronounced as [geoi1].
*杯水車薪 is an exception with 車 pronounced as [ce1] (車 is a classifier here. The above mentioned idioms all have 車 as a noun).
It confused me when my friend wrote: "two of the Mainland dictionaries (including 現代漢語詞典) use [che1] to correspond [geoi1]" and list 閉門造車 as [bi4 men2 zao4 che1] instead of [bi4 men2 zao4 ju1], which correctly corresponds to [geoi1] in Cantonese.
After reading some forums, apparently dictionaries in Mainland China, are contradicting each others, with some listed 'che1' and others listed 'ju1' for all the idioms I mentioned. It means the opinions on how to pronounce 車 in idioms are not unified in Mainland China.
With that said, the question remains. "Is it acceptable to pronounce 車 in the idioms I listed as [che1] in Mainland China?" I mean, if I said: "bi4 men2 zao4 che1" would some people correct me and tell me that I should pronounce 車 as 'ju1' instead? Most importantly, which one do teachers teach to students?