Hey all i wasn't able to post this in the Engine section i guess cause i'm a newbie haha.
Anyways i just finished doing this mod I did this mod a long time ago back when i drove an LS1 Camaro and figured i could do the same thing to my k20 civic.
First here is the picture of the 2 coolant lines that go to the throttle body they are under the intake pipe so you will have to remove that to get to it. (borrowed from the DIY: Tb coolant bypass thread)
Things you need to buy:
1/4 inch to 1/4 inch Universal coupler (you can get at Home Depot in the plumbing/piping section) Looks like this except without the 3/8" barbed side it looks like the long 1/4" side on both sides of the coupler. (picture borrowed from home depot website)
Some small hose clamps (the ones for small tubing, they sell them at home depot as well)
Some rubber caps I think they were called screw head caps, or screwdriver caps (also bought at home depot i got the green ones they are about 1/4" in diameter from the looks of it) *edit* They are called Screw protectors
(by request I updated this to make a step by step version for easy reading, pics/video will be uploaded soon stay tuned)
1.) Remove Intake pipe from Throttle body. You do this by taking a screw driver and loosening the hose clamp attached to the intake pipe on the throttle body, and on the filter box then just slide it right off. (loosen the red circled ones and unclip the yellow circled MAF sensor clip)
2.) Now notice the two lines in the picture above at the bottom of your throttle body, those are your coolant lines to the throttle body. The bottom one is coolant into the throttle body and the top one is the coolant return line to the main engine coolant line.
3.) Take some pliers and squeeze the stock hose clamps and slide them down the coolant lines so they are not clamping down the hose. (In this picture the guy had a screw on hose clamp but they will both look like the bottom hose clamp. They are the kind that you squeeze the two ends together and they loosen up kind of like a hair clamp for girls)
4.) Remove the bottom coolant line by pulling it off of the TB line. (this takes a little bit of force since the lines are so snugly secured onto the TB so don't be afraid to pull hard on it ^^) the bottom coolant line will leak coolant when you take it off so after u take it off direct the hose upward allowing gravity to hold down the coolant in the line and not get it all over your engine. (Also put a rag or something into your air intake pipe so that you don't get coolant in it but if you do just take a rag and clean out the coolant in your intake pipe you don't want that getting sucked into your engine)
5.) Take the top coolant line off that's connected to the TB. (Same warning as the bottom line it's hard to pull off so put some muscle into it, but try not to Yank it, it will slide off)
6.) Now that you have both coolant lines off Take the 1/4"-1/4" coupler and put one end through one of the coolant lines then put your new hose clamps on both lines. (I guess you could use the stock hose clamps too but I just like the feel of the hose clamps that you screw in they just feel more secure to me)
7.) Now put the other 1/4" coupler end into the other coolant line, now you have a coolant circuit!
8.) Move the hose clamps to where u can feel the coupler inside the coolant lines and place them over that area and tighten down. (Make sure it's nice a snug)
9.) Now take your screw protector caps and put them over the TB lines that you took the Coolant lines off of just to plug them up
10.) All done! Clean up and start her up and take it out for a test.
Thank you to Galaxygrey13 for letting me take pics of his car and letting me do this on his car since mine is in the shop.
(I've also left the original post just incase i missed anything)
You basically just take both lines out (careful once u take one of them out it will start leaking coolant out of it, so keep your air intake pipe clear of it or just shove a rag into the intake pipe like i did) The lower line is the coolant into the throttle body line and the upper line is the coolant return line back to the main coolant line to engine. I would suggest take the bottom one out first so you dont have to work with coolant spilling out on you while you take the other line out I made the mistake of taking out the top one first now my hands smell like coolant. Take the bottom line out and point the end up and coolant won't fall out of the tube.
Slide the hose clamps on each tube, but don't tighten down on them, this is just so you don't have to try to put them on once the coupler is in. Then take the coupler and shove it into both coolant tubes making a circuit and allowing the coolant to recirculate back to the engine.
Then move the hose clamps over where you feel the coupler inside the tubes, preferably close to the open end of each tube, and clamp it down nice and tight (this line is under pressure due to coolant running through it so make sure it's tight but not too tight)
Then you take the (screwdriver caps/ screw head caps) rubber caps and slide it over the open metal throttle body lines that you took the coolant lines off of. (mine fit perfectly, they were nice and snug only problem was that they were a neon green color which doesn't match but it's hidden anyways so no big deal)
Then that's it! I DID notice that the throttle body runs much cooler. Before this mod, after i drove around, i touch my throttle body it's hot to the touch about as hot as the intake manifold sometimes hotter. After I did this mod I went for a drive for about 30 mins and i pop the hood and touch the throttle body and it's nice and cool about room temp maybe a little cooler than that.