Heater Core Hoses

[BDE]

Hello Everyone:

I recently bought a 2003 4Runner Limited V8 with dual temperature controls (i.e. the passenger front can get hot air while the driver gets cold air.) It also has a vent near the center console rear (to blow on the back seat passengers.)

I have attached a picture of two hoses connecting my engine to two metal tubes which I think go through my firewall to my heater core. The picture shows where the top hose connects to the top firewall metal tube at one end and to the engine at the other, and also where the bottom hose connects to the bottom firewall metal tube on one end and the other end disappears behind the engine after running to the left a bit.

My mechanic connected them like this after I found out that the heater core had been totally disconnected and asked him to reconnect it. According to him, the hose that is on the top takes coolant into the engine and out from the heater core via the top metal tube, and the hose at the bottom takes coolant from the engine (from the water pump) into the heater core via the bottom metal tube.

I have looked up many diagrams on the internet and still cannot figure out if the heater core uses a specific one of the metal tubes for incoming coolant and the other for outgoing coolant. The diagrams I have seen seem to show that the vents for the backseat passengers have their own heater core and I am wondering if one of the metal tubes leads to that one (in which case both the outgoing tubes/hoses from the heater core are somewhere else and not shown at all in the picture.)

Can anyone help me clarify what the two metal tubes lead to and if it matters which one takes in coolant and which one brings the coolant back out?

Thanks,
BDE

 

[BlackWorksInc]

Couldn't tell you which one is which honestly, not that it should matter; most heater cores I have had the displeasure of replacing didn't seem to have a specific inlet or outlet.

That being said, your current set-up looks exactly like the FSM, so you're good. If it means anything to you, the bottom tube leads to the top of the heater core while the top tube is the bottom of the heater core, which I would assume flow is going to be top to bottom.

 

[V8Man]

I will have to check mine, but its on the way to colorado. most heater cores I've seen the flow is bottom in top out to eliminate air pockets. In some late models the heater is higher than the radiator. I would also suspect that you may have a diverter flap problem or a leaky heater core that was hidden by the previous owner.

 

[BDE]

Diverter Flap?

Hey V8Man,

When I checked out my evap core it was terribly dirty and like caked in mud. No idea how that could have happened! Anyway I had to have a mechanic change it and unfortunatley I could not change the heater core at the same time so that will be a separate several hour job!

Now I am getting a new heater core because I guess its probably just as dirty. Does the heater core contain the diverter flap? What is the diverter flap?

On another note, I hear a gurgling noise sometimes under the dash more or less where I would expect the heater core to be ... not sure if that could be related to the diverter flap thing. I dont think I have a leaky heater core because Im not losing coolant and my carpet isn't wet.

Thanks,
BDE

 

[200mileshighclub]

Hey BlackWorksInc,

This is an old thread, but I'm hoping you could help. I have a 3rd gen 2003 4.0l v6 and am trying to replace the PCV ventilation valve. With my (very) limited toolbox, the easiest way seems to be disconnecting the heater core hoses, removing and replacing the valve, and reconnected the hoses. I'm wondering if there would be any issue in removing the hoses while the car is off - whether it be fluid coming out, pressure release, or anything else. Let me know if there'd be problem or not, or if you know of any better way to replace the PCV valve! Thanks!

 

[twa318]

Hey BlackWorksInc,

This is an old thread, but I'm hoping you could help. I have a 3rd gen 2003 4.0l v6 and am trying to replace the PCV ventilation valve. With my (very) limited toolbox, the easiest way seems to be disconnecting the heater core hoses, removing and replacing the valve, and reconnected the hoses. I'm wondering if there would be any issue in removing the hoses while the car is off - whether it be fluid coming out, pressure release, or anything else. Let me know if there'd be problem or not, or if you know of any better way to replace the PCV valve! Thanks!

Welcome!


PCV is a super simple job, see here for pics: http://www.toyota-4runner.org/4th-gen-t4rs/194970-pcv-valve-v6.html

Not sure what the new member restrictions are in regards to search access, but in the mean time put this code in google.com to find anything on the forums:

site:http://www.toyota-4runner.org/4th-gen-t4rs/ "your search terms here"

 

[200mileshighclub]

Welcome!


PCV is a super simple job, see here for pics: http://www.toyota-4runner.org/4th-gen-t4rs/194970-pcv-valve-v6.html

Not sure what the new member restrictions are in regards to search access, but in the mean time put this code in google.com to find anything on the forums:

site:http://www.toyota-4runner.org/4th-gen-t4rs/ "your search terms here"

Thanks twa318! Very helpful.