Throttle Body Coolant Bypass (with pics), Want to bypass the coolant flow to your Throttle Body on you 5SFE? Options

[Spider77]

So, after quite a few PM's on how to do this I finally broke down and took some pics. You will notice however that I did not put everything back to "factory settings", ie, I just took a few pictures and hope that they'll help the ones who want to know how to do this.
First off though, a warning:
****THE COOLANT WILL BE HOT AFTER RUNNING THE ENGINE, THEREFORE TO AVOID BURNS I STRONGLY SUGGEST THAT YOU LET THE ENGINE/COOLANT SYSTEM COOL DOWN BEFORE ATTEMPTING TO DO THIS, I AM IN NO WAY RESPONSIBLE FOR PERSONAL HARM THAT MAY BE CAUSED WHILE ATTEMPTING THIS, YOU HAVE BEEN WARNED****

STEPS:
1:) You want to start by disconnecting your SRI/CAI/Stock Intake at the throttle body:

2:) Disconnect the 4 Vac lines (three on top, one that sits lower):

3:) Disconnect the Throttle Cables (one for Man, two for Auto):

4:) Remove TB by pulling the 4 12 mm bolts:

5:) Remove TB from Intake Plenum:

6:) You will notice three lines hooked into the TB, two outside line (coolant) and one middle line (vac). You want to "bypass" the TB by linking the two coolant lines together, using a 5/16th brass bard (male to male) fitting and screw clamps to tighten it down. Please do not use existing hardware as its probably been sitting there for a while and chances are it wont stand up. Please use new hardware (screw clamps).




7: After you insert brass barb (male to male fitting) and tighten down the screw clamps, you might want to install some vac caps on the coolant ports. Although I cant say if its required, for me its just piece of mind):

8: Reattach the Vac line (its the middle port)!

8.5: Totally optional, but at this time I did a minor cleaning of the TB, and the butterfly valve. Not required, but while its open, might as well, right?
9: Check your work. This is what you should have, two coolant lines "looped" together, two coolant ports capped (optional), and the Vac line (the middle port) reattached. Make sure that your screw clamps are tight (either use a socket or the right size four point to make sure its super tight...don't want leaks), and again, check another time. Once you are sure everything is done, place your throttle body back on the intake plenum, place the SRI/CAI/Stock Intake back on, and enjoy!

While I can not say this is how it is for different engines, the concept is the same. So, for all those people PM'ing me, this is how you do it (again ,mind you its not a pure step by step, but you'll get the idea), and for those who want to know how to TB Bypass on the 5SFE, here you go!
I hope this can help answer this question to some extent. If anyone sees anything wrong with this (ie mislabeling please let me know so I can correct).
Thanks and hope you enjoy!

[Bitter]

It may just be a coil spring to make sure the IAC fails fully open when it fails? Maybe it is a bi-metal spring and it's a backup in case it fails electrically? Someone should take one apart and find out, I'd be interested to know.

[Langing]

It may just be a coil spring to make sure the IAC fails fully open when it fails? Maybe it is a bi-metal spring and it's a backup in case it fails electrically? Someone should take one apart and find out, I'd be interested to know.

That ISCV looks very similar to the Idle Air Control (IAC) valve on my 2000 Tacoma that I was discussing above. The IAC valve is attached to the TB using four phillips screws (that are hard to get loose). In that photo, you can see at least two of the four screws and see how the ISCV is connected to the TB, just like the IAC is in the Tacoma. The central feature in this photo, where you see two phillips screws, is a cover that would cover the bi-metal spring being discussed. If I remember correctly, there was some kind of cover (less striking) on the Tacoma IAC.

I didn't take that apart since it seemed to be factory preset (notice the yellow paint in the photo?). Also notice in the photo that if you loosened the two screws you could 'adjust' the preload on the spring by slightly twisting the plate and re-tightening the screws. There may or may not be such a spring in the Tacoma IAC, since it is definitely computer controlled (i.e. there is a connector coming off the wiring harness that plugs into wires in the IAC).

I looked up the TB in my shop manual for my 7A-FE engine of my 94 Celica ST, and there was an Idle Up valve that seems to be controlled by engine vacuum, but no coolant hoses running to it. She isn't home today, so I can't visually verify that.

I DID take the IAC valve off of the Tacoma TB, and cleaned and tested it according to its shop manual. Seems the function of the IAC is to allow air to bypass the butterfly valve inside the TB when it is closed (IDLE), so the IAC allows some air to be going into the intake manifold during idle, else the engine could not start.

TESTING THE IAC: When I had the IAC off, and cleaned, I could clearly see the 'valve' was a 'shutter' (rectangular metal door that sounds just like the square hole reported by VavAlephVav) that closes -- or opens to let air bypass the butterfly valve). There is, on the Tacoma, an electrical connector to permit the ECU to control the opening of the IAC valve. There are three electrical pins going into the valve, the center of which carries 12 volts (when under test) and the other two go to coil windings that control opening and closing of the 'shutter'. Two kinds of tests are done on this valve. The first test is to determine the resistance of each coil winding. Though different, these resistances are both in the neighborhood of 20 ohms. The second test is comprised of putting 12 volts on the center pin and then ground on the other two pins, one at a time, and checking to see the 'shutter' opens with 12 volts across one winding, and that it closes with 12 volts across the other winding. The solenoid may be working against. the force of a spring to insure that a failure would leaves the 'shutter' open (to guarantee an ability to idle), but I cannot say for certain. I do not know if the spring in the IAC of the Tacoma, if there is one, is bi-metallic or not.

Perhaps the Celica ISCV is identical in function to the Tacoma IAC valve, but instead of a computer voltage controlling its opening, it uses temperature to control its actions mechanically, by causing a bi-metal spring to wind and unwind, whereas the IAC on the 2000 Tacoma the ECU uses Engine Coolant Temperature (ECT) to decide how much to open or close the IAC valve? But VavAlephVav mentioned that his valve had a vacuum port that he had to suck to determine which direction to install the bi-metal spring. There is no vacuum port on the Tacoma IAC.

This post has been edited by Langing: Sep 12, 2014 - 12:42 PM