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MJEasly
11-08-2003, 11:56
Dr. Lee,

As you know, the 6.5TD has an oil cooler mounted in front of the radiator with oil inlets mounted on the bottom. If changing the cooler, how would one go about not trapping air in the top section? Why doesn
tom.mcinerney
11-10-2003, 17:38
The coolers are designed similar to radiators, with a header either side, flow from side-to- side . I can't directly answer why they don't trap air. Earl's Performance automotive accessories sells thermostatically-controlled sandwich oil-cooler adapters[take oil from beneath filter flange, feed to cooler and return to filter, only when oil hot] . These adapters are described as always running 10% oil-flow thru cooler to purge air. This stuff isn't in experimental stages. The flat plate style coolers on our trucks were designed for aircraft operation, and are very good in adequate air flow.
MJEasly
11-11-2003, 15:03
Well, it looks like when I go to change mine, I'll fill the lines with oil and let it idle a minute or two with the cooler below the oil pan before I bolt it back in place.

Thanks
CleviteKid
11-12-2003, 06:45
Hi Mark,

You asked a good question. When I installed my B&M plate-style tranny fluid cooler, the instructions were to put the fittings at the top, so the cooler would fill with oil before delivering it to the outlet.

As to the factory cooler: any air trapped in the cooler would be compressed to oil gallery pressure, typically 45 psig, (60 psia) which would reduce its volume to 1/4 of original, meaning your cooler is at least 3/4 full. Also, the internal passages may be small enuf that oil is forced to travel up the inlet header and push air ahead of it in all the passages before rejoining in the outlet header and returning to the engine. Also, on a start-up you don't have to wait for the cooler to re-fill before delivering oil to the engine - some of the oil will go straight across the bottom of the cooler and back to the main oil gallery in the engine.

You won't hurt anything by lowering the cooler during refill after an oil change, but I don't think it is necessary, either.

Dr. Lee :cool: