All engine faults/repairs/maintenance Performance/Longevity
Engine air inlet source Hot summer conditions:-
Fortunately, the vehicle's air drag goes down more than the power does in hot ambient conditions, but picking up fresh, cool ambient air is still important, rather than hot engine bay air. The higher its picked up above hot tarmac, the better; there can be a large temperature difference between hot tarmac and air 2 metres above it in summer sunshine, up to 5 degrees C. Engine bay air can be anyone's guess in these conditions, 50, 60 or more? That sucks power and as well as that, means peak combustion temperatures go up and if turbocharged, reduces turbo efficiency giving even more of a temperature rise.
Oil Coolers: Considered very important for longevity of turbo-diesel engined T25's, due to the massive amount of heat generated in these rear-engined vehicles running with hot engine bays. The original fitment oil cooler is really an engine oil/coolant-water heat exchanger, designed as much to warm the oil up quickly as to subsequently cool it. A separate dedicated oil cooler is recommended, especially for 1.9TD and TDi diesels, and even the 1.6's.
Low oil pressure on all these vehicles seems sometimes to be more the result of overhot oil as slack clearances and wear and wouldn't become so critical if the oil temps were kept below the 120C max. Oil temps can easily approach 130C on 1.9TDs if the performance is used and sufficient cooling isn't provided (up-front 19 row oil cooler is recommended). Oil capacity can be increased by using quite large bore oil hoses to front oil-cooler, e.g. 1/2" and even 3/4" bore (the latter increasing capacity to about 7 litres (from 4.5), providing some sort of buffer to short-term oil temp rise and more oil to ansorb any pollutants).