3RZ Water Bypass No. 3 Hose Routing

Can anyone with a 3RZ tell me where this hose connects? 1997 Tacoma Ext Cab

Comes off the tee from water bypass pipe, Toyota calls it "water bypass hose no. 3". Apparently I need to take better pictures on future rebuilds, lol.

 

Does that go to the heater core?

 

It’s a little guy that look like it goes to the charcoal canister but there’s no home for it there. I’ve got a few pictures that show it going under the intake manifold but unfortunately I didn’t grab one that shows where it lands.

 

There are two lines that go to the IAC (Idle Air Controller) on the throttle body, maybe one of those?

 

Yeah I think you may be onto something there, didn't think to look at the throttle body last night. I'll check this evening after work.

 

On the long end of that steel tube ( at very back lower engine)......that feeds into the heater ....splits off into two lines

the big fat one feeds into the heater core or its switch........

the little hose that looks like twisted spaghetti thats marked in yellow, feeds up into the egr valve......thats how egr knows if engine is hot or cold....

then that egr valve has an exit hose.......and that feeds into the IAC.......
thats how the iac knows whether engine is hot or cold......

and with the iac hugging the bottom of the throttle body.....that also preheats the TB when its ice cold outside.....
so it cant freeze up like a scuba regulator in ice water.....
......thats what killed Will Rodgers and Willey Post.......carb froze up within a minute of full power flight....


then that line comes out TB and rejoins into a 'Y' behind the head rejoining the heater core output

that 'Y' mounted to the back of the head is what seats the ECT sensor that tells the ecm what engine temp is....



This is how toyota's cylinder management works from all this..
by controlling inert gases injection.....
keeps/runs the heads cooler.....for very long life
has zero due to epa mandates or milage

 

...



I recommend everyone replace those little hoses with brandnew silicone braided ones from Napa or Amazon

 

Good info here, did some learning on why an IAC valve need coolant lines and it makes sense. I think I can see where it goes in this picture:



Gonna have to source some reinforced silicone lines per your suggestion.

 

Yeah its kinda expensive....use to be able to get at just certain napa stores by ft

but 5 years ago couldnt find and bought a whole roll from amozone

$39 HPS 5/16" ID blue high temp reinforced silicone heater hose 10 feet roll, Max Working Pressure 85 psi, Max Temperature Rating: 350F, Bend Radius: 1-1/4"

Amazon.com: HPS 5/16" ID blue high temp reinforced silicone heater hose 10 feet roll, Max Working Pressure 85 psi, Max Temperature Rating: 350F, Bend Radius: 1-1/4" : Automotive


also bought a 8' roll of 5/16 snowmobile fuel line for like $8 to replace anything with vapors.....like pcv vent line...


that braid hose has gone up about $10 in last 5 yr......
and the HPs large heater core water lines have doubled in that time
.....now $150 for a three piece set.....oooouch

I'd be hard pressed to recommend that much

 

That spaghetti one I could not trust with the silicone......could get pinched or bent over shut

so ....did I not only replace with brandnew oem one.........I have brandnew spare oem one in a sealed pkg
.....for inevitable day they discontinue


just on that one hose I'm a two faced bitoich ......


https://autoparts.toyota.com/products/product/hose-water-by-pass-1626775010

 

Yep, hose did indeed go to the IAC valve, thanks for the help!

To anyone else that has this question and finds this in the future; water bypass hose no. 3 feeds from the hard line tee up through the intake manifold (clips off to the intake for support) and hits the IAC valve on the bottom side close to the valve cover.

 

Prices are only going up from here so not a bad idea at all. If you plan on keeping your vehicle, all rubber/silicone hoses will need replaced eventually. The trick is finding the storage space...