Can someone tell me what the smaller fan on the back side of the radiator is for,is this a fan for the aux. trans cooler.If so what activates it and do you feel another aux in line cooler is necessary when towing.I have elimated the radiator cooler already with the bypass method. Iam planning on towing a 4000 lb trailer and dont want to heat up the tranny.Lastly can you tell me the best place to mount a temp. sending unit.

The electric fan is a two speed deal and turns on in response to engine temperature, not transmission temperature. With the AC off, it will turn on low @ 208 degrees and on high @ 221 degrees. With the AC on, it gets more complicated. There's a grid in the factory service manual that tells you when this fan will kick on and off.

If you tow and you've done the bypass, I'd recommend a second cooler. There's plenty of room up there. I have a picture of my setup in some similar thread around here that I can't seem to find.

08Datsun wrote:If you tow and you've done the bypass, I'd recommend a second cooler. There's plenty of room up there. I have a picture of my setup in some similar thread around here that I can't seem to find.

depends on what year the truck is
the early ('05-'07, i think) have the external trans cooler in front of the right side of the radiator, with components that do not appear to be re-locateable & would be in the way of a second external trans cooler installation on the left side
that's the problem that i've been trying to solve
that leaves the options at either:
installing another cooler behind the existing one
or adding a fan to the existing one, and i'm not sure that either of these options are wise as they might restrict air flow through the existing components and defeat the purpose
or

I installed a fan on my cooler and Im honestly considering taking it off. It does seem to run about 10-15 degrees warmer since I installed it. So yes technically it does block airflow. And with my driving, I havent got to the point of needing the fan. Ive kicked it on for fun sometimes and it honestly doesnt make much difference.

Budrbean wrote:I installed a fan on my cooler and Im honestly considering taking it off. It does seem to run about 10-15 degrees warmer since I installed it. So yes technically it does block airflow. And with my driving, I havent got to the point of needing the fan. Ive kicked it on for fun sometimes and it honestly doesnt make much difference.

good to know, thanks
i'd consider an additional trans cooler in front of the left side of the radiator but that's where Nissan put the power steering cooler on the early models, and it doesn't look like there's any reasonable way to relocate it
and even if there was, blocking air flow to both sides of the radiator might not be too good an idea
sooo..............

Blocking both sides is a valid concern. I happen to have mine set up this way right now. I have both a cooler and a fan on the passenger side, and the factory cooler on the driver's. There's been no cooling issues - so far. It did the King's Canyon grind, trailer in tow, without issue. There is still a nice sized area under the grille where air comes through. The setup I have I did simply because I had those parts lying around.

You still have the option of doubling up the coolers on the same side like the Xterra guys have been doing. Another option is just to replace the factory cooler with a much thicker one.

eieio wrote:

Budrbean wrote:I installed a fan on my cooler and Im honestly considering taking it off. It does seem to run about 10-15 degrees warmer since I installed it. So yes technically it does block airflow. And with my driving, I havent got to the point of needing the fan. Ive kicked it on for fun sometimes and it honestly doesnt make much difference.

good to know, thanks
i'd consider an additional trans cooler in front of the left side of the radiator but that's where Nissan put the power steering cooler on the early models, and it doesn't look like there's any reasonable way to relocate it
and even if there was, blocking air flow to both sides of the radiator might not be too good an idea
sooo..............

Honestly it is my belief that people are blowing this cooler thing out of proportion. I bypassed the radiator and run only the external cooler. According to my temp gauge, the hottest temps I have seen was 210 degrees. That was stop and go driving on a 100 degree day. And as stated before, the fan didnt cool it but maybe 5 degrees. This temp measurement is the fluid going into the cooler. On most days with regular driving, I see temps from 165-185......at highway speed it stays around 165. So yeah, I wouldnt sweat adding another cooler unless you are gonna be towing a lot.