PSA: Check your in radiator transmission cooler for plug!!!!

Summary - buddies sister's 07 4runner v6 w/ A750 trans, no tow package. Overheated trans into limp mode which prompted a full transmission flush with the addition of an aux trans cooler installed upon her return home from her trip. We found the following factory plug in the inlet (top port) of the radiator trans cooler blocking any external cooling of the trans! CHECK YOURS PEOPLE!




Long story.

Mid July, hot as hell, Buddies sister decides she wants to take a detour through sequoia national park on her way to meet all of us at our yearly lake trip. Her 07 4runner 4wd sport has been an awesome rig, no issues because well we know how bulletproof the Single VVTI 1gr and A750 trans is! Its 105+*F out and shes cruising at 10mph up steep grades and AT temp check light comes on, followed shortly by full limp mode. Lets it cool down for an hour, makes it to the lake, then proceeds to go drive another 500 miles through Yosemite and mammoth area before getting home where my buddy and I can have a look. We figured lack of tow package aux cooler and slow steep driving in hellish heat were to blame.

So a BnM auxiliary cooler was purchased, we installed it and then proceeded to do a full transmission flush. Pulled the last soft line on the return side of everything to push old fluid out and, nothing. Absolutely NOTHING came out. Perplexed we continued to go down the line till we got to the softline at the top of the radiator (first inlet to any auxiliary cooler). Pulled it and found a factory plug in the nipple blocking all flow of any transmission fluid. It had been this way for 150,000 miles!!!!!!

Needless to say its a testament to the trans but also, do yourself a favor, if you havnt done a trans flush and verified that you do actually get trans fluid flow through all the coolers, DO SO!

 

its gone 11 years without the rad cooler working? did you ever do a drain and fill and if so what did fluid looks like?

 

man thats insane! I need to check this!

 

yup!

Flushed the trans added the cooler, and she drove from CA to Texas without issue and hasnt had any issues since!

 

Why would that plug be installed in the first place?

 

Some new radiators have little red plugs to keep out debris during transit or protect the fittings I assume someone was sleeping on the assembly line. Have heard of something similar on a Ford truck with an aftermarket radiator. Most plugs I've personally seen wouldn't allow you to assemble without removing.