Transmission Cooler Radiator Bypass (92 240 AT)

dbille · Post by **dbille** » 22 Nov 2020, 20:52

Hey all, I recently bought a 92 240 Wagon and discovered the dreaded transmission oil cooler radiator failure. Needless to say I have not been driving it, but want to install a transmission cooler to completely bypass the radiator, then flush the cooling system and see if the radiator is salvageable (car doesn't overheat). And luckily there is no sign of coolant in the auto transmission (will be doing a drain or flush). But I also just generally would like your opinions' on a trans cooler bypass.

So I am curious what size trans cooler you think would be sufficient for a bypass?
Also, does anyone know what size hardware to use to plug the trans line inputs on the radiator when doing a bypass?
And what mounting location do you think would be optimal on a 240 and why? It seems many recommend in front of the AC condenser.

Thanks for your input with this!

Post by **volvolugnut** » 24 Nov 2020, 12:12

I think you may be better off getting another used radiator with the built in transmission cooler. Cost should be moderate and my experience with several 240 automatics, is they are fairly durable. Adding a separate cooler risks getting too much or too little cooling if the wrong size or location is used. With the built in AT cooler you will get very stable AT oil temperature.
volvolugnut

lummert · Post by **lummert** » 25 Nov 2020, 12:16

I'm guessing you may not want to run an external cooler if you live in a colder climate. The trans will take longer to warm up in cold weather.

Post by **MoVolvos** » 25 Nov 2020, 17:01

dbille wrote: ↑22 Nov 2020, 20:52
So I am curious what size trans cooler you think would be sufficient for a bypass?

Thanks for your input with this!

Still finding time to install the Hayden on my 03 S80 T6 but the same has been on the 03 Odyssey bypassing the radiator for perhaps close to 3 years. Van has over 230K miles and I believe it's the original transmission. I haven't yet, but if the winter is colder than usual I may zip tie a piece of plastic on the face of the cooler. Summer hasn't seen temps over 180 degrees using an infrared gun so it's been doing well.

Honda Odyssey's 3.5L motor, plus the size of the van has been known to eat transmissions but this one is still doing okay even with the radiator bypass. If the incoming air/ambient temp is 100 degrees, it's still much better than running the transmission fluid through the 180 degrees coolant temp. It is installed before both the radiator and air conditioning condenser.

Hayden Transmission Cooler / With Complete Installation Kit 26,000 GVW (OC-1405)

https://www.ebay.com/itm/Hayden-Transmi ... 2749.l2649

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dbille · Post by **dbille** » 29 Nov 2020, 11:42

Thanks everyone for your responses. I think I'll start by updating everyone of the oil in coolant investigation. I ended up installing a Hayden cooler similar to the one MoVolvos linked to on the front of the AC condenser. I then flushed the cooling system, put in fresh coolant, and have been driving it around for about a week. And I would feel the trans lines for temperature after a drive and they certainly weren't too hot.

There is still no coolant in the engine oil, and no oil in the coolant reservoir (sounds like my head gasket is fine). There is also no coolant leaking from the radiator where the stock trans cooler inputs go. And upon removal, inspection, and cleaning of the coolant overflow reservoir, I did notice some residual oil in a recessed hole on the top of the coolant reservoir, which was confusing at first (why is this covered in oil?).

This leads me to believe that someone before me topped up the coolant reservoir with engine or trans oil. My neighbor had suggested this to me but I dismissed it! Occams Razor or something right?

However, this is actually the best case scenario. And I think I will reattach the transmission lines to the original radiator cooler and keep an eye on the coolant for contamination and just switch it back if I find anything funky.

And I will just leave the extra trans cooler installed since I am going to be driving this loaded for 2000 miles across the country, and may want to hook up the extra cooler for long drives and hot Texas weather.

Thanks again for all you input!