300 tdi radiator engine oil cooler

**TonyC** · 25th February 2025, 03:00 PM

Originally Posted by shack

I'd probably like them separate, but 1 good point of the integrated is that it helps the Auto warm up.

After that, the Auto adds more heat to the engine and the engine adds more heat to the Auto... Depending on operating conditions of course.

I've never actually got to the bottom of what an ideal Auto Trans temp is... But it's better under 100°.

Modern engines often operate at that temp or hotter.

Isn't the auto trans cooler in a D1 separate?
At least it is in the one I'm trying to remove the motor from.

It's the engine oil cooler that's in the radiator.

Tony

**TonyC** · 25th February 2025, 03:06 PM

Originally Posted by MLD

i've researched alot about engines, cooling, autos and the like for the LS conversion. GM with the 6L80 thermostat was 98 deg C from its intro until 2020. in 2020 GM recommended as a service item to replace the thermostat for that auto to 79 deg C. GM found the higher thermostat was causing premature failure of the gearbox. Granted they didn't move fast on implementing the change. A mate who is one of the best auto specialists on the east coast is of the view that you can run the 6L80 without a thermostat in Australia. He also buys random stuff from the auctions because it catches his eye, so i'm not convinced of his sanity. I am going with the 79 deg C thermostat and a large separate cooler as a compromise between all the opinions.

The higher operating temps of modern engines is mainly to do with emissions. There is a reasoning for the near 100 deg C thermostat temps on forums that at that temp the moisture is boiled off the oil. But lets be honest, there are 2 flaws in that logic. First, engine oil and transmission oils operate under pressure. increase pressure, increase boiling point of the fluid. So the boiling point of any moisture in the system is not going to boil off at 100deg C, but a higher temp based on the pressure. for example, the coolant system that operates at 17psi has a boiling point of around 114/116 deg . The second point, the logic relies on some magical threshold that below boiling temp, the moisture remains in the oil and above that temp it boils off. Evaperation starts much lower temps. Granted oil at 80 deg might take longer for moisture to evaporate, but it will do so.

rant over. carry on gents.

The oil in the engine sump and trans pan are at atmospheric pressure, or near enough.

Tony

**RANDLOVER** · 25th February 2025, 06:45 PM

I suspect the water and oil will emulsify and the moisture won't boil off.

**MLD** · 25th February 2025, 10:25 PM

Originally Posted by TonyC

The oil in the engine sump and trans pan are at atmospheric pressure, or near enough.

Tony

good point.

**MLD** · 25th February 2025, 10:36 PM

Originally Posted by RANDLOVER

I suspect the water and oil will emulsify and the moisture won't boil off.

I'm not convinced that is correct. Emulsification is typically as a result of an addative. Soap is an emulsifier of oil by breaking the surface tension of the oil globule permitting it to form smaller aggregated balls of oil. The water and oil never mixes (becomes homogeneous). The oil is held in suspension in the water (due to their respective denisty). If you left the mix to settle, it would find its own laying according to its density. If the oil and water do not bond, the water is a free agent to boil/evaporate off.

I'm getting off the topic of the OP.

**shack** · 26th February 2025, 08:06 AM

Fwiw, any moisture in engine oil will absolutely boil off if the engine is hot enough and it runs for long enough.

You will be surprised how much will boil off actually.

As a side point to back this up, for many years car owners manuals made the point that if you only did short trips and monitored the oil level it may never move, but then you do one long trip and the oil drops drastically, this is likely due to a buildup of moisture from short trips that gets boiled off on a long one.

**Blknight.aus** · 26th February 2025, 10:29 AM

Originally Posted by MLD

i've researched alot about engines, cooling, autos and the like for the LS conversion. GM with the 6L80 thermostat was 98 deg C from its intro until 2020. in 2020 GM recommended as a service item to replace the thermostat for that auto to 79 deg C. GM found the higher thermostat was causing premature failure of the gearbox. Granted they didn't move fast on implementing the change. A mate who is one of the best auto specialists on the east coast is of the view that you can run the 6L80 without a thermostat in Australia. He also buys random stuff from the auctions because it catches his eye, so i'm not convinced of his sanity. I am going with the 79 deg C thermostat and a large separate cooler as a compromise between all the opinions.

The higher operating temps of modern engines is mainly to do with emissions. There is a reasoning for the near 100 deg C thermostat temps on forums that at that temp the moisture is boiled off the oil. But lets be honest, there are 2 flaws in that logic. First, engine oil and transmission oils operate under pressure. increase pressure, increase boiling point of the fluid. So the boiling point of any moisture in the system is not going to boil off at 100deg C, but a higher temp based on the pressure. for example, the coolant system that operates at 17psi has a boiling point of around 114/116 deg . The second point, the logic relies on some magical threshold that below boiling temp, the moisture remains in the oil and above that temp it boils off. Evaperation starts much lower temps. Granted oil at 80 deg might take longer for moisture to evaporate, but it will do so.

rant over. carry on gents.

when the oil is past the pump in the galleries and bearings on the crank its under pressure, in the sump and getting splashed around inside the crank case it should be at atmospheric pressure, the mositure thats getting boiled off is generally the water thats created as a byprodct of combustion. The poor crank case ventilation of the old 3.5 v8s used on continual short runs without enough time to reach operating temperature and sufficient duration once there to evaporate the water is a great example of this. The rocker cover that went to theventilation system would usually be relatively clean, the side that didnt was usually full of junk.

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