Heat smells like melting plastic
10-15-2017, 09:09 PM
#1
Drifting
Thread Starter
Heat smells like melting plastic
I noticed today that when I have heat coming through the vents after a while I get a melting plastic odor. I'm sure it is not antifreeze - I know that smell - so I don't suspect a ruptured heater core.
My wife and I were on some backroads today and we had windows down with heat on set to 80. The engine had been up to full operating temp for at least 15 minutes prior to turning the heat on. After about 20 mins of heat a melting plastic odor came on quickly and strongly. I turned the heat off and within a few minutes it disapates. Turn heat on and it comes back.
Any idea what this may be? Should it matter, the car is a 94 with C68. Nothing seems out of place under hood - no wire loom touching the headers.
My wife and I were on some backroads today and we had windows down with heat on set to 80. The engine had been up to full operating temp for at least 15 minutes prior to turning the heat on. After about 20 mins of heat a melting plastic odor came on quickly and strongly. I turned the heat off and within a few minutes it disapates. Turn heat on and it comes back.
Any idea what this may be? Should it matter, the car is a 94 with C68. Nothing seems out of place under hood - no wire loom touching the headers.
10-16-2017, 12:28 AM
#3
mine was the spark plug wire holders. a piece had broken off and was melting on the manifold. the heater drew outside air in and it smelled.
10-20-2017, 01:10 PM
#6
Drifting
Thread Starter
Ok - so I've found nothing happening under hood that would cause this smell. In addition, if I let the car up to full operating temp and THEN
turn the heat on the smell won't show up for 15-20 minutes. And also, once the smell is present if I open the hood and sniff around there is no smell by the engine. Whatever is making this odor is happening INSIDE the hvac unit.
The only time I get a smell is during use of heat. So this has to be something that is getting hot from the heater core and once the air is channeled over the heater core the smell is picked up and transmitted to the cabin. What in holy hell can this be? If I stick a hose in cowl and flush with water am I asking for loads of trouble or should the water come out the a/c drain? Obviously I'd use a gentle stream of water. Any chemical type product to mix in to clean things out?
side note: many many years ago I had a pos chevy beretta. That car has some kind of foam liner inside the air box that has disintegrated. It smelled (don't recall if it's similar to this smell) and blocked airflow. Any such thing on the C4? My airflow is fine.
and lastly - I stated in an earlier post in this thread but will mention once more just to reaffirm. The heater core is for sure not leaking - this does not smell like coolant, there is no steam, there is zero loss of coolant.
turn the heat on the smell won't show up for 15-20 minutes. And also, once the smell is present if I open the hood and sniff around there is no smell by the engine. Whatever is making this odor is happening INSIDE the hvac unit.
The only time I get a smell is during use of heat. So this has to be something that is getting hot from the heater core and once the air is channeled over the heater core the smell is picked up and transmitted to the cabin. What in holy hell can this be? If I stick a hose in cowl and flush with water am I asking for loads of trouble or should the water come out the a/c drain? Obviously I'd use a gentle stream of water. Any chemical type product to mix in to clean things out?
side note: many many years ago I had a pos chevy beretta. That car has some kind of foam liner inside the air box that has disintegrated. It smelled (don't recall if it's similar to this smell) and blocked airflow. Any such thing on the C4? My airflow is fine.
and lastly - I stated in an earlier post in this thread but will mention once more just to reaffirm. The heater core is for sure not leaking - this does not smell like coolant, there is no steam, there is zero loss of coolant.
10-20-2017, 01:18 PM
#7
Racer
Apropos of nothing
This won't help, but it may amuse you. Many years ago I worked for a Volvo and Alfa Romeo dealership. I was lent a new Alfasud for demonstrations and my own use. When I used the air vents or heater, a smell would enter the car that took my breath away.
After much searching, the workshop discovered that the alternator was faulty, and was always charging the battery, even when fully charged. This was boiling the battery acid, and the fumes were being blown into the car. Scary stuff!!
After much searching, the workshop discovered that the alternator was faulty, and was always charging the battery, even when fully charged. This was boiling the battery acid, and the fumes were being blown into the car. Scary stuff!!
Last edited by maddogwyatt; 10-20-2017 at 01:19 PM.
10-20-2017, 02:17 PM
#8
Drifting
Thread Starter
This won't help, but it may amuse you. Many years ago I worked for a Volvo and Alfa Romeo dealership. I was lent a new Alfasud for demonstrations and my own use. When I used the air vents or heater, a smell would enter the car that took my breath away.
After much searching, the workshop discovered that the alternator was faulty, and was always charging the battery, even when fully charged. This was boiling the battery acid, and the fumes were being blown into the car. Scary stuff!!
After much searching, the workshop discovered that the alternator was faulty, and was always charging the battery, even when fully charged. This was boiling the battery acid, and the fumes were being blown into the car. Scary stuff!!
10-21-2017, 09:34 AM
#10
Zen Vet Master Level VII
let the car up to full operating temp and THEN
turn the heat on the smell won't show up for 15-20 minutes. And also, once the smell is present if I open the hood and sniff around there is no smell by the engine. Whatever is making this odor is happening INSIDE the hvac unit.
The only time I get a smell is during use of heat. So this has to be something that is getting hot from the heater core and once the air is channeled over the heater core the smell is picked up and transmitted to the cabin. What in holy hell can this be?
turn the heat on the smell won't show up for 15-20 minutes. And also, once the smell is present if I open the hood and sniff around there is no smell by the engine. Whatever is making this odor is happening INSIDE the hvac unit.
The only time I get a smell is during use of heat. So this has to be something that is getting hot from the heater core and once the air is channeled over the heater core the smell is picked up and transmitted to the cabin. What in holy hell can this be?
I doubt you have melting plastic issue. You state that you only smell this odor inside your car (the HVAC cavity) and only hot. Although water temps are hot, it won't melt plastic.
Now, what I think is happening, is that some of the foam insulators or rubberised insulation is coming loose and resting on hot water tubes- this will get "melty" and have a definite plastic-ish smell.
My guess is the smell will dissipate over time however, if you want to get to the bottom of it you will have to take apart your system-- doing a full on heater core repair-- to find your issue.
A 94 heater core repair is a Beeotch- 12-14 hours at a competent shop (I asked my tech).
10-23-2017, 06:14 PM
#11
Intermediate
I've experienced similar odors after a long run of heat at higher temperature setting. I now never use heat more than 74-75 degrees and have sweatshirts in storage bins for early spring/late fall. If that's not enough, the top goes back on.
10-23-2017, 07:10 PM
#12
Drifting
Thread Starter
I did have the heat set at 80. I think 85 is as high as it will go. Will try it at 74 next time around and see what happens.
11-20-2017, 11:27 AM
#13
Drifting
Thread Starter
Just a follow-up. I drove it this past weekend with the heat set to 74 - no smell. Not a great solution but a solution nonetheless for now. I’m not diving in to replace the heater core and inspect whatever else is going until it fails.
