owenxguo

Asked some friends where is this going they said can not see another site
anybady can tell me?
I think I got big trouble might have to remove lot of things
help plz

jimmyv13

That should go to the coolant nipple on the backside of the waterpump housing.

owenxguo

where?

NZConvertible

Here:

owenxguo

oh Are you sure?
Cause............
look my pic
there is wut I am doing...........

jimmyv13

When you bypass your BAC, you can connect those two coolant nipples with a coolant line.

owenxguo

Actualy............I dont really understand???????

owenxguo

you mean like this?

1SxyRXy

yeah.. it looks like it does go there because i know when i took mine off, coolent came out of it.

SonicRaT

iTrader: (6)

Uhm. You've got it all wrong. Once you run the coolant line from the block to the back of the water pump, you no longer have coolant running from the throttle body to the BAC valve, so that line that's connected to your bac valve (in the first picture, with the open nipple) Is a complete waste of space.

NZConvertible

Yes I'm sure.

What you've shown in your picture is exactly what I told you. Normally coolant flows from the nipple on the rear plate to the bottom of the TB, then from to top of the TB to the BAC valve, then from the BAC valve to the nipple on the back of the water pump. If you want to bypass the TB (I presume that's why you're asking this) then you need to run a long hose with a preformed 90deg bend from the rear plate straight to the water pump, as you've drawn. You don't tee off to the BAC valve, that's pointless.

BTW, as advice for the future, if you'd studied the FSM you'd know all this.

owenxguo

ok thx
I am asking this because my old engine is gone
so this is a S5 J-spec engine and i replace all old parts on it except the turbocharge
but when I almost done them , I cant remember wuts this connect. But i checked the pics which I took b4 i take off the old engine, I think there was nothing connect on BAC valve b4(but not sure)
so just ask to know where is connect
thx a lot guys!

owenxguo

and i have a question
what's BAC valve for?
and if it just need coolant come in, I can find any nipple which has coolant come out is that right?

NZConvertible

The Bypass Air Control (BAC) valve is the ECU's main idle speed control valve. When you turn on loads like the A/C, headlights, rear demister and fan it allows more air to bypass the throttle (hence the name) to keep the idle speed smooth and avoid stalling.
The water that passes through it doesn't really do anything, except maybe stop it from seizing in extreme cold. You probably don't need the coolant connections at all, just run the bypass hose as you drew in you picture.

SureShot

Unless you need the cold start fast idle cam, that circuit in unnecessary, in the way, and can fail without warning.
Just cap both ends.
It's the best part of the TB mod.