Transmission cooler installation

Tiny
MRENGINEERGUY
  • MEMBER
  • 2008 LEXUS IS F
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I’m replacing the radiator with a better cooling one not stock and it came with a transmission cooler. My question is, it doesn’t use any old hardware but the two lines coming from the transmission mark blue and red does it matter what side it goes into on the transmission cooler?
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Wednesday, July 22nd, 2020 AT 10:47 PM

5 Replies

Tiny
STEVE W.
  • MECHANIC
  • 15,358 POSTS
Usually the red line is the hot fluid coming out of the transmission and blue is the return line to the sump on the transmission. If you have a single cooler with no flow markings it doesn't really matter, if it has flow markings then the red would go to the in side and blue to the out side. If you have a cooler in the radiator as well as a cooler outside the radiator then yo would normally route the fluid through the radiator cooler then to the external cooler.
Be sure that an external cooler is in the path of airflow, it won't do it's job if the air cannot get to it.
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Thursday, July 23rd, 2020 AT 3:06 AM
Tiny
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Thank you for your answer. These coolers don’t need to be pre filled correct? The system will run it course when I top off the radiator fluid.
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Thursday, July 23rd, 2020 AT 4:49 AM
Tiny
STEVE W.
  • MECHANIC
  • 15,358 POSTS
Correct, they are basically the last thing the fluid does on it's trip through the transmission and back to the pan. So get it all in place. Start the engine, cycle it through the gears and then check the fluid level and top it up.
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Thursday, July 23rd, 2020 AT 10:48 AM
Tiny
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Thank you, thank you, clarity makes these projects well worth it. Stay safe!
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Thursday, July 23rd, 2020 AT 3:23 PM
Tiny
STEVE W.
  • MECHANIC
  • 15,358 POSTS
You are welcome. Thank you for using 2CarPros.
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Thursday, July 23rd, 2020 AT 5:24 PM

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