Got a 2000 4Runner Im fixing up, not my daily driver. Got a slow coolant leak from a "nipple" at the firewall on the passenger side, at just about the height of the exhaust manifold. Its below the spot where the AC hoses enter through the firewall. I checked the manual but couldnt find any reference. It looks to be part of the Heater assembly?

My question is I know there should be an L-shaped aluminum tube attached to the nipple, but does anyone know if thats supposed to be open to air? Is it a breather or exhaust of some sort for the heater core? Since its leaking coolant, I know its connected directly to the heater core. It does leak slowly as the engine runs, but not when the engine is off.

Im tempted to simply seal it shut with some toyota rtv....

Without looking at mine to confirm, that sounds like the drain tube for the heater core/AC evaporator. You may have a leak in the heater core which would obviously only present itself when the water pump was running. If it's the tube, sealing it off will just cause it to drain into the cabin.

It's probably your rear heater lines, most of us bypass the rear heater so we don't have to fix the lines, it takes all of 3 minutes and its just unclipping and reclipping some rubber hoses. Ill elaborate more later.

So a blockage or leak in the rear heater would cause a drip out the front pitot tube? I'll search the forum for the rear heater fix....thx

Pitot tube? You a pilot? I think I know what your talking about. It's the little aluminum tube that comes out of the rubber grommet. It normally serves as the ac evaporator water drain, but apparently (and conveniently) also vents the heater core in the event of a leak. Sounds like you may need a heater core after a little more troubleshooting.

Hope this helps!

-John

not an actual pilot, but have put my time in flying. It just looks like a pitot tube, so why not. Exactly right Sawgunner, it does peek out from a little rubber grommet. Yeah, Im afraid you're right. I guess I should have known flipping a car wouldnt be easy.

Previously, I found the 90-degree rubber hoses feeding the upper AC/Heater lines (near top center of firewall) completely blocked with rusty sediment as this vehicle had a bad coolant leak and was parked for a year. I should have known simply replacing freeze plugs in the engine wouldnt solve it. Im going to have to completely check the coolant path in this truck, or I'll never be done with it.

Looks like the heater core is just another small alum radiator? Is it possible to repair a leak in these at the local old-school rad shop? I see even the crap replacements at autozone are nearly $200. I would rather not spend that much.

200 for a heater core?

Here ya go! Same as in parts stores!

SPECTRA PREMIUM 99287 Heater Core | eBay

I didn't read the whole thing you wrote, my bad, I would still check the rear heater lines right next to the frame rail on the passenger side of the car right under the body, it's 2 lines running parrarell.

Thanks for the ebay part! Only problem I see is the tech manual diagram doesnt show the pitot tube, and the picture on ebay/autozone doesnt show it either. Im going to tear things down before I commit to making this purchase.

But yes, first thing I will check those rear heater lines. I dont recall seeing them there and have had this truck on the lift many times by now (twice engine removed!) and didnt see anything running near the cat (which I replaced), but will check again. We are talking about outside of the vehicle, not inside, under the carpet?

That tube you are seeing is from the A/C Heater core drain pan. Not the actual HC. Remove the glove box, Heater core is enclosed in the housing behind it. right above the blower motor!

Does the entire dash have to come out to access the HC and pan? Anyone done this? I wouldnt think so but cant count the number of times Ive been wrong...

This is a 2000 Sport Pkg but I cant recall if that means rear heat. Im not seeing those rear heat hoses at all. I wonder if the truck doesnt have it....

ok, finally have time to address this, and hoping I dont have to remove the entire dash. Does anyone know if that is necessary, or can the heater core be squeezed out through the hole made by removing the glove compartment?

Oh, and I verified this 4runner does NOT have the rear heater option, so this leak has nothing to do with the rear heater.

I realize this is an old thread that never posted a solution to the problem. I found others that seemed to end with no resolution to the problem. I'm having this very same problem with my '99 4Runner withe the V6 and rear heater option.

A week or so ago, I noticed a small puddle on the ground underneath the front passenger side. I crawled underneath the vehicle and noticed a slow drip coming from small tube with a 90 degree elbow below the passenger side firewall. Upon further examination I confirmed it was coolant. The coolant level was also down around 16 ounces or so, and I'm having to add more in small amounts on a regular basis. I'm assuming this is caused by a leak in the heater core? If so, where can I find a tutorial for replacing the unit? Thanks for any help......

This might help.

Heater core removal

google site:toyota-4Runner.org/3rd-gen-t4rs/ heater core replace