a heat exchanger bypass system comprises a liquid circuit , a first fluid circuit , a second fluid circuit , a first heat exchanger , a second heat exchanger , a liquid bypass line and a heated bypass valve . the first heat exchanger thermally couples the first fluid circuit to the liquid circuit . the second heat exchanger thermally couples the second fluid circuit to the liquid circuit . the liquid bypass line circumvents the first heat exchanger . the heated bypass valve controls flow through the liquid bypass line .