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BILLSHEILA is on the right lines I think.
Several years ago I was flying my 337G from France to the UK. It was a much much colder than ISA day. Seem to remember something like minus 20c at 12000feet. We had been in the cruise for over two hours when I noticed the rear engine oil temp gauge "going off the clock". The problem was confirmed by low oil pressure. I reduced power on the rear and started a descent. The intention was to divert to Cardiff in Wales. At about 7000feet the oil temp started to reduce together with an increase in pressure. Power was gradually increased and the engine ran normally and the flight continued to Leeds Bradford.
I reported the problem to the Chief Engineer at Knight Air ( who were very "au fait" with the 337 ) and we concluded that there is a thermo valve in the oil cooler which stops oil going thro' the cooler when cold. In this instance because ambient was minus 20 or so, the cooler had shut off, then causing the oil to overheat then the low pressue. If there is then congealed cold oil in the cooler, the valve will not open to let the hot oil through. Then overheating. The only reason oil started to flow thro' the cooler again was due the the rise in ambient temperature.
Hope all this makes sense.!! It's my input for what its worth !!
Sunnysky
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