Horrid chemical smell from defroster vent

Ok folks I need some brain power because everything I’m coming up with isnt going to be fun…

2019 tundra, bought new, 49500 miles.

lots of upgrades but nothing in the coolant system or dash area around the heating system.

Issue: When I run the truck for a long time (1 hour or more solid) and then turn off the truck (rest stop) then back on fairly soon the heater vents make a god awful chemical smell that smells like burning plastic or chemicals. No smoke, no clouds or mist just chemical smell. I blast the heater with all the windows down and two minutes later its gone.

Interesting, last summer I had to top off the coolant but it was only half gallon. I wrote it off as its been almost 4 years.

Now I can only guess I have a small leak in my heater core or hose clamp at the core but looking online Im not seeing much. Does anyone know a way to isolate and test the core without ripping the dam dash out? I thought about pulling the coolant lines on the firewall and adapting a rubber hose with an air compressor fitting along with a air gauge to pressure it up and let it sit.

Also does anyone know how to change out the heater core on this beast?

Any other ideas before I jump down this rabbit hole….

 

What does your cab air filter look like? I’m thinking you would have replaced that already, but if not, do that first. Check for any signs of rodents too.

 

Filters good and I fixed a rodent issue years ago. This is defiantly a strong chemical smell

 

Is I possible you ran over a plastic bag or anything like that? My wife has a similar situation on a car….I crawled under and there was a melted plastic bag under the car. Tried to scrape off as much as I could but it lasted a long time.
If it’s a coolant type smell then I would bet you have a leak or heater core problem although I would be surprised if a heater core went bad on a 2019.
Either way, good luck and hope you figure it out soon.

 

Checked the underside today and found nothing as far as plastic trash.

Anyone have the steps for changing out the heater core?

 

I wouldn't change heater core out unless you know 100% it's leaking. Any vapor or humidity with the smell? Windows fogging?

 

No humidity, or wet damp carpet. What else could get into the air system that would smell like chemicals. It’s not outdoor air either because it happens when I’m in the woods alone too.

 

As stated before, there is no way I would tackle changing the heater core unless you’re 100% sure that it’s the culprit. The chemical smell could be many things. In the jeep wrangler I have, you would know it was the heater core when there was a puddle of antifreeze in the passenger floorboard. I would take it to a mechanic to diagnose and then decide if it’s something you would be comfortable doing. In order to change the heater core you likely have to rip apart the entire dash.

 

Just went out to check the truck and look around. Lost another half gallon of fluid. That’s a gallon in about 8 months…. The carpet is perfectly dry.

 

Is your battery leaking? Maybe you have a freon leak? Does it smell like something else that would help us identify it? Does it smell like febreeze or like battery acid or....

Usually coolant just smells sweet

 

It smells like a dry, stale, air. It’s hard to explain it doesn’t smell like anything really. It takes your breath away. It has been very cold lately and yesterday never got out of the 20’s… Im using an AGM battery.

 

It definitely don’t smell like fabreeze lol

 

AGM still utilizes lead-acid technology. The smell would be....pungent like sulfur.
If you're talking coolant, it's almost like...chemically maple syrup?

Really hard to describe smells. Hope you find the issue.

 

If it was coolant it would smell almost sweet like said above. Transmission and differential oil smells awful and will take your breath away - if it’s possible that you’re leaking that fluid into a heat shield or exhaust it makes sense that it COULD be that. Not sure why it would only happen at start up though.

 

Actually, here you go OP: https://www.cenex.com/about/cenex-i...g-page/general-interest/diagnosing_car_smells

Any sign of theft / attempt on your catalytic converter?
How about wear on brakes? E-brake left on?

 

The Freon in my last fridge that failed smelled like magic markers

 

The way you describe it now, it could be just your typical stinky evaporator smell that is pretty common. If it were mine, I would try a good cleaning before tearing anything apart. Good luck.

https://www.youtube.com/watch?v=eRy23TFpM4I

 

Cats look good, brakes are good. Im going to see if I can find my old radiator coolant pressure tester and hook it up over night. It really doesn’t smell like anything listed. It’s just a chemical smell that steals your breath away. I walked down to a local shop not far from my place. They said Toyotas good about adding a weep drain hole in the bottom of the heater box that is either vented through the firewall or underneath the passenger seat/center console. If i can’t find the vent and the pressure test holds I might have to take it in for diagnostic st a bare minimum. The dang truck is not drivable at this point.

 

Burning wires, etc. Could be rodent issues.

 

Just a thought but if you have a bore scope you could drop the blower motor from under the glove box and run it down the vent to see if anything is going on in the heater evaporator under the dash. Try this first.
https://youtu.be/fPOfecY7MF0

 

If it’s undriveable, you must really have a problem going on. Take it to a professional and have it looked at.

 

You could pop the lid on the coolant overflow bottle when the engine is warm to compare the HVAC smell to super long life coolant. Notice I said overflow bottle, NOT the rad pressure cap, as that will try to burn you.

If it doesn’t smell like coolant, but is more of a nasty sock smell, you should also check that the drain tube isn’t plugged. I know you said you couldn’t find the drain, so you’d either have to search again, or take it in to have it checked out.

Does it have the same smell after a short drive? I’m also wondering if the blower motor is overheating for some reason, and causing the stench.

 

Pressure test the coolant system?

 

Watching this thread. Keep us updated OP!

 

Super frustrating issue - I want to know what it is. Keep us posted with updates.

The fact that the odor only occurs after long running and then a stop (to me) indicates that being in motion stops it from being in the cab. For what it's worth that sounds to me like an engine bay or undercarriage source, rather than the heater core, which is closed and if it's a problem should smell bad while underway as well

 

Ok so today I played around with the truck. My coolant pressure tester doesn’t have an adapter to fit the truck. Removed the trans and cat guard plate and found the drain. Its wayyyy up there in the tundra but by the time I found it, it was dark outside.

I played around with the ac controls. Fired the truck up all hvac settings no smell. Let it idle for about 10 minutes the smell started to creep in. Once the smell was there slightly i changed the vents from defrost to face vents and holy crap was it bad. Let it run for another five at full flow windows down while I was outside of the truck. Ran for another five most of the smell went away. Changed back to defrost and bam nasty ass crap again. Called a buddy over to take a wiff lol. He agreed doesn’t smell sweet at all but nasty chemical mixed with musk. Once again no plastic I’ve ever burned smelt like this. Left it idling in the driveway for a little longer with the vents on blast. Now it just smell hot but not nasty.

Couple hours later went to the gas station for fun and to see what it would do. Drive 3 blocks and turned on the defrost windshield mod and dam the smell was super strong asap. The truck wasn’t even warmed up. Turned it all off and gave up.

I’m taking it to the local shop in town. They are a good old boy shop that has been around forever. I’ve never used them but all my neighbors do and come in highly recommended. They said for $50 (half hour) they will play around and see what they can find. Obviously not tearing anything apart just testing the feon, coolant, and checking the drain hole. If they can’t figure out the smell I’m calling Toyota. Less than 50k miles and cant even drive a few blocks. I love the truck but wtf is this about.

 

So couple other things I thought of today. This happened in the past but only last 2-3 minutes very short periods and only like once or twice in the last 3-4 years. This time it’s not going away. When it started this time I was using 4high driving in the snow and ice but all on a horrid paved road. Not off roading just a nasty snow storm.

my kiddo had frozen hands from playing in the snow so on the ride home we turned to face vents to get the rear vents pumping out the best we could. That’s when the smell started. Come to think of it we NEVER use the face vents unless its summer. In Oregon its always on defrost and feet during the winter.

There was a ton of deicer on the roads and i wonder if that could be my chemical smell. But I have zero clue why it would only smell from my vents. Under the hood and outside there is no smell it’s only from my vents.

Also a few months ago I did have some mice issues finding poop on my hvac filter. I pulled the front cowl and screened up the fresh air intake and never found another turd by my truck. The air filter didn’t have any holes so i never thought they made it through that area. I do wonder if maybe they got past the filter and messed up the blower but I would think it would make noise and would have acted up months ago.

I don’t know, I’m out of ideas. Hopefully tomorrow we will have a better guess.

 

Thanks for the updates, let us all know how you make out.

 

My bet is a dead mouse.... Or a nest with a few dead baby mice.

Where? Who knows.

Hope you get it figured out. Make sure if you or someone else finally finds it to clean / sanitize / deodorize 10 times better than you think is needed or it will never go away.

 

X's 2 on the dead mice theory. I think you have dead, rotting mice corpses in the vent system.

Will be very interesting to read the conclusion to this.

Goos luck! Hope you get it sorted sooner rather than later.