ATF heat exchanger bypass?
07-05-2009, 04:29 PM
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ATF heat exchanger bypass?
My 1986.5 uses an in tank ATF heat exchanger and a small cooler in front of the radiator. I am scared to death of the heat exchanger failing and introducing engine coolant to the transmission. I wonder if it would be a good idea to bypass the radiator heat exchanger and use the cooler alone. Is the factory unit in front of the radiator sufficient to cool the transmission properly? I realize that doing that would make the transmission heat up slower in the winter, is that a problem if synthetic ATF is used? Any thoughts will be appreciated!
07-05-2009, 07:02 PM
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While such a failure is possible, and does happen, it is rare. I don't think that it is worth worrying about unless you have some indication (such as, you know that you have twisted the cooler fittings trying to remove them).
07-05-2009, 08:21 PM
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The stock cooler pair does a more-than-adequate job provided the engine coolant portion of the radiator is in reasonable shape. Remember that the whole system was designed for all-day driving at autobahn speeds, so what we do in the US is generally a lot less load.
The radiator cooler sections for oil and ATF are some pretty nice aluminum pieces. The coolant side looks a lot like the air side of the radiator itself. It's pretty robust, and as others mention its failure will almost always be linked to physical abuse from someone trying to get the hoses loose without counterholding the cooler ring. There are o-ring seals where the nozzles pass through the plastic radiator end tank, there to keep coolant from leaking around the fitting and out to the engine bay. No coolant-to-ATF seals at all.
Unless you are supercharged or turbocharged, and need the extra radiator capacity used by the transmission, I wouldn't be concerned. Even then, the too-common trans cooler 'solution' just adds another exchanger in front of the radiator and AC condenser. Just moves the heat transfer around in the same airflow, with the radiator and engine coolant still treated to the trans heat load in the end.
The radiator cooler sections for oil and ATF are some pretty nice aluminum pieces. The coolant side looks a lot like the air side of the radiator itself. It's pretty robust, and as others mention its failure will almost always be linked to physical abuse from someone trying to get the hoses loose without counterholding the cooler ring. There are o-ring seals where the nozzles pass through the plastic radiator end tank, there to keep coolant from leaking around the fitting and out to the engine bay. No coolant-to-ATF seals at all.
Unless you are supercharged or turbocharged, and need the extra radiator capacity used by the transmission, I wouldn't be concerned. Even then, the too-common trans cooler 'solution' just adds another exchanger in front of the radiator and AC condenser. Just moves the heat transfer around in the same airflow, with the radiator and engine coolant still treated to the trans heat load in the end.
