Confirm my diagnosis!

[rwordenjr]

Had light smoke randomly start coming out of vent today on a drive. Got home and went right to look at the heater core weap hole… light drip. That will never happen unless heater core is leaking correct ?

View: https://youtube.com/shorts/E-VtRvax-NU?si=1SqfV11_o3pXv3kl


View: https://youtube.com/shorts/dIhnQpB5kA4?si=DEgMPpwrr80ZK_Z-

 

[Noobz347]

Water coming from the drain in the engine bay is normal. Even on defrost, the A/C compressor runs and causes condensation that will run out the drain.

The appearance of 'steam' out of the vent indicates water in the vent and that can come from a leaking heater core.

Check for water/antifreeze on the passenger side carpet.
Check for the smell of antifreeze or a film forming on the inside of the windshield.

 

[rwordenjr]

Water coming from the drain in the engine bay is normal. Even on defrost, the A/C compressor runs and causes condensation that will run out the drain.

The appearance of 'steam' out of the vent indicates water in the vent and that can come from a leaking heater core.

Check for water/antifreeze on the passenger side carpet.
Check for the smell of antifreeze or a film forming on the inside of the windshield.

No film, and nothing on carpet. I swear the fluid in the video looks clear (water like) so I was a bit confused. Once it cools down, I’m going to put my finger on the weep hole and see what color for sure. No accessories were on either when smoke started coming out of vent.

 

[rwordenjr]

I started car again and put finger down where the weep is hole… sweet smell . Put on heater full blast and it still works good

 

[rwordenjr]

You can hit it with the harbor freight pressure tester. It connects in place of your radiator cap. Then you pump the little pump and watch the gauge. If it's not holding pressure, have somebody sit inside the car while somebody else pumps and see if they can hear the leak.

Even with a pinhole, your heater will continue to work as long as there's coolant cycling through the system bringing heat from the motor. But the leak also keeps the system from being able to get up to pressure. Unpressurized cooling system will boil faster.

This should be the reason why was getting light smoke out of vent right ? Also, interesting note that on my coolant reservoir tank, there is the full hot and full cold. Mine is at full cold but when I parked car earlier today after drive and car was hot, the reservoir tank did not rise to full hot.

 

[rwordenjr]

I can't say for sure thats why you're getting smoke/steam through the vents. This could also be caused by something outside the car smoking and getting pulled through the fresh air duct. You are correct in that it is a possible cause. It is not the only possible cause.

Like was mentioned earlier, turn on the defroster and let it run. If its the heater core blowing steam, you should see signs of it on the glass.

Ran on defrost for 5 min straight but no change to glass

 

[rwordenjr]

Won’t consistently smoke either. Can’t get it to do again. Definitely light drip out of that weep hole though. Sticky sweet

 

[rwordenjr]

None has dripped on floor yet. I live in California so not worried about heat working but I don’t want puddle of coolant on my carpet. I have the Dorman bypass kit I bought years ago just in case. Even with bypass kit though, I’m still at risk to have coolant on carpet once ehh?

 

[rwordenjr]

Not if you bypass the heater core, then blow the core out with air before you cap it off on the firewall.

I'd do a pressure test before I bypassed the heater core, though. You may be barking up the wrong tree.

This what you talking about ?

 

[rwordenjr]

Thats one of them. I think the maddox one they sell is cheaper, but doesnt come with as many adapters because they're sold separately. It should still have everything it needs to test the cooling systems in the fox cars.

 

[AeroCoupe]

I’m just going to say it. The heater core is leaking or fluid is leaking where the hoses connect to the heater core and are somehow traveling down those tubes and into the hvac box. Nothing else is going to be sticky sweat. Condensate from running the AC is just water. My money is on the heater core. NPD sells new copper ones so you may try them.

 

[rwordenjr]

I’m just going to say it. The heater core is leaking or fluid is leaking where the hoses connect to the heater core and are somehow traveling down those tubes and into the hvac box. Nothing else is going to be sticky sweat. Condensate from running the AC is just water. My money is on the heater core. NPD sells new copper ones so you may try them.

Bone dry on the hoses going to heater core at firewall and bone dry on the opposite end where they go into back of intake area

 

[nickyb]

Take a sample piece of carpet ,put it on passenger floor,bypass the core and fogettaboutit

 

[rwordenjr]

Take a sample piece of carpet ,put it on passenger floor,bypass the core and fogettaboutit

You think leave heater lines uncapped ?

 

[gkomo]

I’m just going to say it. The heater core is leaking or fluid is leaking where the hoses connect to the heater core and are somehow traveling down those tubes and into the hvac box. Nothing else is going to be sticky sweat. Condensate from running the AC is just water. My money is on the heater core. NPD sells new copper ones so you may try them.

Did the new updated brass ones come out? I was supposed to get notified but never did.

 

[nickyb]

You think leave heater lines uncapped ?

Yes, hag mine like that for seven winters here in Nevada,finally changed the core and all good since.

 

[rwordenjr]

We’re here for now.

 

[AeroCoupe]

Did the new updated brass ones come out? I was supposed to get notified but never did.

Engine Post in thread 'Is this a good heater core?'

Dec 30, 2025

I emailed NPD yesterday and got a response this morning with regards to their brass/copper heater cores.

Our M-18476-2B copper/brass heater cores are still in production and not yet available. We have 50 on order and are awaiting fulfillment from the manufacturer. We do not have an ETA, but we know they are in progress.
We appreciate your patience!!!!!!
Please let me know if you have any other questions.
Best Regards,
Derek De Beliso

Customer Service Manager

National Parts Depot
900 S.W. 38th Avenue
Ocala, Florida 34474-1883
800-874-7595 (Toll Free)...

• AeroCoupe

• 

 

[Qtrhrse23]

I've seen smoke coming from my vents on very humid days. Many a time.

I could see why you think heater core, but that isn't the only scenario that produces the smoke in vents.

Another is when it's 100+(Texas) and you turn the AC on. When it's real bright in car from sun, the smoke is there. No wet carpet?

And the coolant won't rise in the overflow everytime.

 

[Qtrhrse23]

Yes, hag mine like that for seven winters here in Nevada,finally changed the core and all good since.

What's a winter in Nevada like? Just curious. I'm guessing you'd only need the heat is for defogging in morning and night.