Stock Trans Cooler BTU Rating

[heckler40]

I am up this year on the 2010 Pathy for the bypass. But, I am having trouble finding the BTU rating of the stock in rad cooler. Any ideas? I am probably going to go with B&M as I have used them a few times before.

Thanks!

[smj999smj]

If your Pathfinder was made in North America, there is no need to add an additional trans cooler for the bypass. The factory installed, auxiliary trans cooler does the job quite well for those who have done the bypass. IMO, if one is considering spending money to add an additional air to liquid cooler to work in conjunction with the factory air to liquid cooler, one would be better off saving the money and purchasing a replacement radiator, instead. Aftermarket radiators can be had for less than $100 and have had no problems with cross-contamination issues.

[heckler40]

The main concern I have with that is the line in the radiator is to warm up the fluid faster. This tells me the aux cooler doesn't have a valve that shuts when its cold, like the B&Ms.

Can anyone confirm this?

[smj999smj]

The factory auxiliary trans cooler does not have a valve to bypass it when the fluid is cold. If used with the radiator's integral cooler, the trans fluid should warm up rather quickly and a bypass valve would normally not be needed. Being that the trans fluid is synthetic in the R51, it would take some extremely cold temperatures to cause viscosity issues with it. If one was using a Pathfinder in that sort of environment, which would likely create a lot of other issues, one would definitely want the trans fluid to run through the radiator to warm it, rather than allow it to simply bypass the air to liquid cooler and be sent directly back to the transmission. The B&M trans coolers typically start around $75 and go up from there; aftermarket radiators for the R51s sell for the same price on Ebay and have not been plagued with the cooler failure issues like the original OEM Calsonic units.

[heckler40]

You will always have vis differences at different temps. We just had >-20F here. So, that's the concern.

Anyone know the specs on the aux cooler? Make and model? Thanks!

[smj999smj]

Yeah, that's pretty cold, but the pour point on most atf's is around -40 to -50 degrees F. You might consider AMSOIL; they have a Nissan-matic Type "S" compatible ATF that has a pour point of -60 degrees F. Seeing temps below 0 degrees F. is even more reason to not bypass the radiator's integral cooler, rather, it would be better to replace the radiator and retain the function of its cooler. If you want to replace the auxiliary cooler with the B&M, that would be an option, but I see no benefit of running both the Nissan auxiliary cooler AND the B&M unit.
As far as an answer to your question regarding the specs on the factory cooler, I don't think you are going to find it. I don't recall it ever being mentioned on the forum and I doubt that Nissan has published that info. You could try calling Nissan's customer service hotline, 1-800-NISSAN-1, and asking them, but I wouldn't hold my breath for any information that's useful. Still, doesn't hurt to try.
The part number is 21621-EA50A if it's on the right side and 21606-ZS20A if it's on the left side in front of the A/C condenser.

[heckler40]

Thanks, would replace it. I do like that it has brackets and is not right up against the radiator. Would need to fab those up.

Regarding the sides, is that if you are facing the front? Or sitting in the vehicle facing the front?

[smj999smj]

If you're in North America, left side is driver's side; right side is passenger side.

[Kestral]

With my 2012 I have driven in -20F and up to +95F towing a 5,000 pound camper with my AC on full going up hill and I have had no problems at all. I have confidence in the trans cooler.