YOU SAID:

You make my undercarriage warm.

INTO JAPANESE

私の脚を暖かくします。

BACK INTO ENGLISH

My legs warm.

INTO JAPANESE

私の足は暖かい。

BACK INTO ENGLISH

My feet are warm.

INTO JAPANESE

足が暖かいです。

BACK INTO ENGLISH

Warm feet.

INTO JAPANESE

足を暖かく。

BACK INTO ENGLISH

Warm feet.