I used to have an RX-8 and I did the throttle body coolant bypass. This was the best way I have heard it explained.

Many cars run engine coolant through the throttle body in order to warm it up so the throttle body doesn't get filled with ice due to a mix of cold temps, humidity, and condensation. This is done because car manufacturers cannot design a car to work for "most" people, they are expected to make cars that work in any condition.
Lucky for almost all of us, we don't live in subarctic locations... It's a no brainer for anyone living in the south.
The throttle body's purpose is to control the amount of air that goes into the engine. With 180-200 degree coolant running through it, we are essentially heating up the air moments before it goes into the engine.

 

As I understood it the coolant line was to keep the throttle body from overheating b/c of the Intake Manifold temp...the line is supposed to come from the side of the waterpump that pumps in cooler coolant, then the coolant is run through the throttle body for cooling, just like some F150's have the oil filter coolant line.

 

Hmmm -- which is the right answer then? Does it HEAT the throttle body or COOL the throttle body??

 

i believe this is right. when i was younger i worked for a catering company and one of the work vans had a 351 and it was known to have throttle sticking problems when it was hot and i got stuck with that van during one job and it stuck open at WOT on the highway. after the mechanic finally looked at it he determined that someone had bypassed that TB cooling at one time and the TB was getting too hot and warped causing the butterfly's to stick. once the coolant was ran through the TB again it worked fine.

 

WOW!!!





WOW!! It's amazing how when you said the right answer you think to yourself 'DUUHH of COURSE that's what its for!!!'

Makes PERFECT sense now!

The throttle body barrels and butterfly maintain tight tolerances -- if it gets to hot it warps ever so slightly preventing the valves from closing - thus the coolant line prevents this!

GREAT ANSWER - THNX! And also a great SAFETY tip -- that story you told of the butterfly getting stuck open at WOT is enough to scare anyone to NOT bybass this line -- wow - I never knew that's what it was for!

 

Notice how close the EGR is mounted to the Throttle body. Mucho Hoto! I'm voting for a "modulation" of the T/B temp. both high & low temps.

 

i tell you that was a lesson in driving for me, i was maybe 17 at the time and it scared the **** out of me. when that kind of stuff happens you dont immediately think about killing the ignition, first instinct was to slam on the brakes but even with both feet pressing the brake that 351 at WOT easily overtook that braking system. i collapsed both front rotors and blew both rear wheel cylinders and overheated the trans. after what felt like an eternity i finally thought to kill the ignition. lesson learned the hard way for a young inexperienced driver.

 

Sweet lucifer - that story is scaring the out of me and I'm just sitting there in the house! Man that must have been something...

Now I think about those who commented here how they lived in hot climates and bypassed this...

On a side note, I generally avoid WOT in any vehicle for fear of what you just discribed! That since the butterfly valve never typically opens that wide that the tube is not 'keyed' ,for lack of a better word, for the valve to open without getting stuck.

 

This makes perfect sense too! But I suppose the TB is not getting anything but cold water flowing through it on a cold start-up -- so logic would suggest that the point is to heat it rather than cool it.

Its confusing because on some other cars the TB is heated by a coolant line which opens up a wax pellet that kicks down the high/cold idle...

These coolant lines are common on most TBs of many cars - now I know not to mess with them....

BTW - to the MODERATOR: ...for reference, how HOT was the outside weather that day you almost perished??

 

i dont remember it being terribly hot, just a normal summer day here. maybe 70-80 degrees id guess.