Trans Cooler Bypass/Temp Sender All In One

Budrbean · Postby **Budrbean** » Tue May 18, 2010 1:59 pm

Ok so after arguing with my pressure port and still not getting the dang sending unit to thread in, I gave up and came up with a better idea. I undid my previously bypassed radiator setup and installed a 3/8 in. tee. Two ends I installed barbed hose connectors and the top, the temperature sending unit. Turned out quite nice and its an all in one package. Plus this should theoretically be where the hottest fluid is because its the intake hose for the cooler. So now Im waiting on my new fan (org one was defective)....I have all the wires ran and ready to hook up.

**For anyone considering this.....learn from my mistakes. You have to ground the sending unit because obviously its not grounded in this method. You MUST ground it under the part where the sending unit screws into the tee or adapter. If you ground it where the sensor hooks up, it will ground your connection to the gauge and it will show 250 degrees at all times. Apparently there is some sort of insulator between the two. Hope that makes sense.

Fossilfuleburner · Postby **Fossilfuleburner** » Tue May 18, 2010 9:32 pm

What temperatures are you reading? I'm really curious to know what they are under normal driving vs climbing a long hill.

Budrbean · Postby **Budrbean** » Wed May 19, 2010 4:33 am

Only got to do a little driving yesterday and it read just above 100. I'll let ya know more tomorrow.

Budrbean · Postby **Budrbean** » Wed May 19, 2010 9:32 am

I did about a 15 mile drive today at highway speeds and the highest I saw it get was around 165 degrees. Im guessing the fluid is gonna read hotter in this location so Im expecting to see it around 180 at most times in normal driving.

eieio · Postby **eieio** » Wed May 19, 2010 9:47 am

Budrbean wrote:I did about a 15 mile drive today at highway speeds and the highest I saw it get was around 165 degrees. Im guessing the fluid is gonna read hotter in this location so Im expecting to see it around 180 at most times in normal driving.

at those temperatures, do you still think a fan is necessary?

Budrbean · Postby **Budrbean** » Wed May 19, 2010 9:50 am

Definitely not necessary. Thats why Im just putting it on a switch so I can flip it on when towing or in a lot of stop/go traffic. Just a nice option to have when needed and not much more $$$ to add to the project.

Budrbean · Postby **Budrbean** » Wed May 19, 2010 1:54 pm

Alright so heres the real verdict. Just got home after driving about 50 miles. At highway speeds is stays around 160 degrees. But it doesnt take much of a lead foot to throw the temp to it. Literally one stop at a red light and a quick take off will rocket it up to 180 almost instantly. Of course once the air gets flowing it goes back down. Also its interesting how riding behind another vehicle will keep the temps around 10 degrees hotter. I can see myself on the highway searching for clean air like a NASCAR driver LOL. I didnt think the temps changed so much but you'd be surprised. If I had a 180 degree sweep, the gauge would travel about as much as the speedometer at times.

So considering I did see 180 a few times, its definitely a good idea to have the fan....especially if towing. And if there is anyone doing the bypass without an external cooler, Id be willing to bet you are well over 200 degrees....not a good idea.

Outside temps were around 75-80 degrees

eieio · Postby **eieio** » Wed May 19, 2010 3:04 pm

It sure would be nice to see some comparative pre-bypass figures

bellwilliam · Postby **bellwilliam** » Wed May 19, 2010 4:13 pm

eieio wrote:It sure would be nice to see some comparative pre-bypass figures

I doubt by-pass changes much under towing condition. coolant enters radiator around 200F when engine is completely warmed up. it looks like with towing, transmission fluid temp is going to be 180F +, so radiator will neither cool or warm transmission fluid significantly.

I would like to see if fan makes a difference while towing at 60MPH.

Fossilfuleburner · Postby **Fossilfuleburner** » Wed May 19, 2010 7:24 pm

Budrbean, the temperature readings you provided are very informative. Please keep us posted as you accumulate more drive time and a wider range of driving conditions. I expect to see much higher temperatures when towing and when there is a prolonged strain on the transmission. For example, when towing up some long hills. The continued high temperatures coming out of the tranny (where you're measuring) will eventually raise the fluid temperature in the pan so the fluid going in the tranny will be hotter causing the fluid coming out to be even hotter. The needle on your gauge may be pinned on 250! I've seen my temps (after the cooler) at 210-220 before. This was from towing on a 90 degree day.

It sure would be nice to see some comparative pre-bypass figures

The pre-bypass figures would be the same. The temperatures Budrbean is reading is at the transmission output, before the radiator cooler.

I would like to see if fan makes a difference while towing at 60MPH.

The fan should not make a difference at 60mph. The purpose of the fan is to generate airflow when no airflow is present (vehicle stopped or traveling slow). At 60mph, the trans cooler is already getting the maximum amount of airflow across it.

pawjr74 · Postby **pawjr74** » Wed May 19, 2010 7:35 pm

Does anyone know what is the max trans fluid temp considered safe for the Pathfinder?

Budrbean · Postby **Budrbean** » Thu May 20, 2010 5:36 am

pawjr74 wrote:Does anyone know what is the max trans fluid temp considered safe for the Pathfinder?

Ideally for any automatic transmission, 180 or below would be perfect. It is said that if you keep temps below that at all times, you can actually get 100,000 miles out of your trans fluid. Every 20 degrees above that you can cut that mileage in half. 220 starts to enter the danger zone and constant temps above 240 will start to deteriorate the seals.

bellwilliam · Postby **bellwilliam** » Thu May 20, 2010 11:10 am

Fossilfuleburner wrote: The fan should not make a difference at 60mph. The purpose of the fan is to generate airflow when no airflow is present (vehicle stopped or traveling slow). At 60mph, the trans cooler is already getting the maximum amount of airflow across it.

are you saying I shouldn't turn on the fan, even if I was towing at 100F weather going uphill, as long as I am at freeway speed ?

bellwilliam · Postby **bellwilliam** » Thu May 20, 2010 12:27 pm

op:

where did you buy the adapter (with 1/8" NPT) ? everywhere I looked online is 5/8" hose adapter. not 3/8".

thanks

Budrbean · Postby **Budrbean** » Thu May 20, 2010 4:09 pm

bellwilliam wrote:op:

where did you buy the adapter (with 1/8" NPT) ? everywhere I looked online is 5/8" hose adapter. not 3/8".

thanks

I went to a local Ace hardware/building supply store. They were in the plumbing section with all the brass fittings. Im told Lowes and Home Depot carry them but I havent checked.

Trans Cooler Bypass/Temp Sender All In One

Trans Cooler Bypass/Temp Sender All In One

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