New radiator or Radiator bypass and add aftermarket cooler?

I've got a 2006 Nissan Pathfinder SE 4WD with the potential problem of coolant and transmission fluid mixing in the cooler in the bottom of the radiator. I was wondering if I can get away with just bypassing the radiator cooler and adding a Hayden 679 external cooler. I feel like it would keep it cold enough I was just wondering if it would over cool it. I live in NC and sometimes it gets below freezing in the winter and I don't want to over cool it if it's possible. If I got a derale Transmission thermostat then it would end up costing as much as a new radiator. What would be the best option and do I really need the derale thermostat? Btw there is already a factory external cooler as well but it seems too small and I plan to tow occasionally.
 
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JC1

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Are you planning on changing the radiator? I would change the radiator to get the leak issue resolved. If there is a factory cooler already you are probably ok with towing using that existing setup.
 

Dogred08

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Monroe, North Carolina, USA
I wasn't planning on changing the radiator because it's not leaking I was just wondering about preventing it from possibly happening by bypassing the stock radiator cooler and adding an extra external cooler. I just didn't want to over cool the transmission if it's possible.
 

Astro14

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If you don't want to cool it too much, then add the thermostat. Is total cost a big concern? You can do a thermostat, remote filter, and new plate-type cooler for about $150 in parts. Bypass the factory system, make changing the filter much simpler, and increase cooling. Here's a write-up on how I modified my Volvo - note that I've done all three of them the same way, just have pictures from the first one. Now, in my case, I wasn't worried about contamination, so I left the factory radiator cooling loop in place. You could easily delete that loop to allay your concerns. https://www.volvoxc.com/forums/showthread.php?27334-02-XC70-Transmission-Flush-From-Bottom/page2 I should add that this transmission is known for failing in Volvos of this year. I've got over 258,000 on the XC-70 on the original transmission. I contend that longevity is due to better cooling and reasonable fluid changes.
 
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Dallas
Replace the radiator first. The reason for the Strawberry Milkshake Of Death is the original in-radiator coolers were a bit defective and would leak. Even if you bypass the stock trans cooler, you have the problem of it then just leaking coolant onto the ground when the cooler goes instead. Replacing the radiator has to be done first.
 
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Alberta
if a new radiator has been updated and doesn't have the same potential issue, I would go that route. You won't overcool the fluid in SC if you choose to bypass and add a bigger oil to air cooler either, but the potential for the coolant in the original radiator to pass into the defective oil cooler is still a possibility, even when it has been bypassed, possibly leaking or getting contaminated, which is why I would replace the original radiator completely if possible with an updated version that won't leak.
 

Dogred08

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Monroe, North Carolina, USA
Is the derale thermostat the best thermostat option? I already have the Hayden 679 I got a discount on it for about 38 bucks and the derale thermostat is around 50. And a new radiator of decent quality seems to be around 160. And there is already a filter in the pan so I'm not sure if an in line filter is totally necessary.
 
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Dallas
Originally Posted by Dogred08
How could it still contaminate if it's completely bypassed? I was obviously gonna seal the Barb's on the end of the radiator to keep it from possibly leaking coolant on the ground.
The coolant could become contaminated. Capping the barbs off with vacuum caps and hose clamps isn't a great idea - those usually fail in a few months. If you buy a new Nissan radiator, it will have all the fixes - some of the aftermarket ones are copies of the original, defects and all. Also, the plastic end tanks on those radiators mean they do eventually need to be replaced anyway - the similar one on my 4Runner finally failed this January after being in service some 20 years (and it probably should have been replaced 3-4 years prior due to developing issues that could be seen in visual inspection). The 4Runners also have the SMOD issue, though to a lesser degree and it takes longer than the Nissans do. I would replace the radiator if for no other reason than age alone and then hook up the trans cooler you bought in series with the one in the radiator.
 
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Any 15 year old plastic radiator is on borrowed time. If you're going to touch this at all, change out the radiator and be ready for another 15 years.
 

Dogred08

Thread starter
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65
Location
Monroe, North Carolina, USA
What radiators would you recommend? They all look about the same just prices seem to vary. There's a no name on eBay for about 60 and prime choice on Amazon for 64 a koyorad for 141. And quite a few others but they all look the exact same is there really a difference?
 
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Dallas
Originally Posted by Dogred08
What radiators would you recommend? They all look about the same just prices seem to vary. There's a no name on eBay for about 60 and prime choice on Amazon for 64 a koyorad for 141. And quite a few others but they all look the exact same is there really a difference?
Yes, there is a big difference. The Koyorad should be okay, they're a Nissan supplier and will have updated their product. The no-name or random aftermarket one will generally not hold up in a Nissan or Toyota and will likely have the same defective cooler design. Go with a Nissan or Nissan OE radiator, don't go cheap. Don't forget to replace the radiator cap with Nissan or Nissan OE while you're at it.
 
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Dallas
Also, Nissan has the Value Advantage line, which is aftermarket parts that pass Nissan testing. You can get that for less than the original - Rock Auto carries the Nissan Value Advantage version of the radiator for $204. Rock Auto also sells a Denso radiator (another Nissan supplier) for $115.79, which would be what I'd get. Check any radiator bought through the mail carefully for damage, they're often not packed well.
 
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125
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Dallas
Originally Posted by Dogred08
Is a OSC radiator a good option I'm trying to avoid using Rock Auto I've had bad experience with them on defective parts. it has the brass Barb's and looks identical to denso
No. Amazon has the Denso radiator as well: https://www.amazon.com/Denso-221-3409-Radiator/dp/B004J317JC The Denso part number is 221-3409. Summit Racing and others carry them. You can also go with the Koyorad.
 
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Messages
691
Location
Connecticut
Originally Posted by Astro14
If you don't want to cool it too much, then add the thermostat. Is total cost a big concern? You can do a thermostat, remote filter, and new plate-type cooler for about $150 in parts. Bypass the factory system, make changing the filter much simpler, and increase cooling. Here's a write-up on how I modified my Volvo - note that I've done all three of them the same way, just have pictures from the first one. Now, in my case, I wasn't worried about contamination, so I left the factory radiator cooling loop in place. You could easily delete that loop to allay your concerns. https://www.volvoxc.com/forums/showthread.php?27334-02-XC70-Transmission-Flush-From-Bottom/page2 I should add that this transmission is known for failing in Volvos of this year. I've got over 258,000 on the XC-70 on the original transmission. I contend that longevity is due to better cooling and reasonable fluid changes.
Based on Astro's post in the xcvolvo forum I installed the Volvo OE Setrab remote AT cooler in the 240 wagon. Normally the AT fluid cools only in the radiator. Volvo didn't include a thermostat with the remote AT cooler. Apparently they didn't feel one was necessary. I use this car primarily for long distance trips in the summer. It's heavily loaded with 2 mountain bikes, a rocket box, an awning, gear, luggage and people. The decrease in coolant temps was immediately apparent. During cruise or climbing the coolant temps were lower than the similar trip the previous summer. The highest AT temp was 187 degrees, recorded at the top of Mt Lemmon in Tucson - a 36 mile climb. I concur with Astro that regular fluid changes and lower fluid temps should help the unit last a long time. An interesting side note concerning the lack of a thermostat. I purchased the cooler from a Volvo 240 enthusiast who lives in Nenana Alaska. He had it on an 89 240 - his daily driver back and forth work in Fairbanks and Anchorage. He never bothered to add a thermostat and said the tranny shifted perfectly. He got tired of the automatic and swapped a manual in its place.
 
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I've had the in-radiator trans cooler bypassed in my truck for 15 years. No trans-cooler thermostat either. Never a problem.
 
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Colorado
I have a 2010 Frontier I bought in 2016. I had a warranty provided in purchase which was for 4 years or to 100,000 miles. My warranty was to end on Jan 1 of this year. A week before the end of the coverage, I had radiator replaced, transmission serviced and a few other simple things done. Cost me 1,100 plus change. He is a little pricey but any thing replaced is guaranteed for 3 years parts and labor regardless of mileage. Shop is AAA approved so maybe that is why.
 
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