Tata Motors' Jaguar Land Rover has announced an additional week of production stand down from 8 to 12 April due to potential Brexit disruption.
Yesterday, Ford said a hard Brexit would cost it as much as US$800m (GBP614m) this year alone as a result of World Trade Organisation (WTO) tariffs and the weakening pound.
Sky News said this was one of the biggest individual company hits forecast so far from the UK crashing out of the EU.
Ford executives, who had already outlined plans for a wide-ranging restructuring of operations in Europe, had privately calculated a no-deal departure would have a severe impact on the company's profits in the first nine months of Britain's post-Brexit existence.
Honda said earlier this month its Swindon plant in the UK would shut down for six days in April as part of the company's Brexit planning measures. It said the step was needed to ensure it was able to adjust to all possible outcomes caused by logistics and border issues.
The firm said it would help in recovering lost production if shipments of parts were held up at borders.
In a statement, the company said: "We are planning six non-production days in April 2019. This is to facilitate production recovery activity following any delays at borders on parts.
"These contingency provisions have been put in place to best mitigate the risk of disruption to production operations at the Swindon factory."
Other UK car manufacturing companies are also making contingency plans for the UK's exit from the EU on 29 March. At this late stage, it remains unclear what border check changes may be needed because a proposed exit terms deal between the UK and EU is yet to be ratified by the UK's parliament. If the deal is in place, new border checks on traded goods are expected to be minimal, but a so-called 'no-deal' or disorderly Brexit would likely see a raft of new checks on UK-EU trade, as well as new tariffs.
Carmakers with UK plants are worried because of the high volume of UK-EU trade in components.
Honda's UK car plant employs over 4,000 and makes the Civic.