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Discussion Starter #1
Hi Team M5,

I was at the track this past weekend and encountered an interesting issue....

So, here in the PacNW we get a lot of rain which means that at the track you will often need to run the heat to defog the windscreen or keep you warm while running with windows down. This weekend was no exception!

Day 1 @ Portland International: No Rain meant the heating / cooling system was off all day. No issues, car ran great!
Day 2 @ PIR: Rain Showers.

Session 1: Wet. I head out for a few laps and return early to inform our Novice group leaders of current track conditions. As I pull up, I start to smell a strong plastic odor. It is coming from the driver side up near the fire wall. No smoke - just smell. I park it for the session and investigate. Found nothing. Ran at Idle with the heat on and the smell did not really come back.

Sessions 2 and 3: No Rain - Heater Off. Only a slight odor the second session and nothing the third session.

Session 4: Rain - Heater On. Ran the full session. Burning plastic smell returns.

The car shows no issues other than the smell. No extra dash lights, no electrical gremlins manifesting, no loss of power.

Has anyone had something similar? Any Ideas?

Thanks!
 

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Have you checked the condition of the engine firewall (open the hood and look at the very back of the engine below the wipers)? They are known to crumble after a decade or so and should be replaced. Maybe one of the broken plastic bits was too near the engine and started to smolder.
 

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When my other car had the burning plastic smell, it was actually oil from the valve cover gaskets dripping on the exhaust. Easy to rule out at least.
 

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Discussion Starter #4
Thanks for the replies.

I removed the plastic cover at the rear of the engine compartment a while ago because it was crumbling. It is possible I missed a couple pieces and they fell onto the exhaust or something shifted but I was not smelling anything leading up to the event.

The covers have a small leak in on the lower front corners but I do not think it is happening fast enough to cause the smell.

I will keep monitoring and see what I find. Everyone else feel free to keep sharing ideas :)
 

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When you say "heater on" do you mean the fan? If you get the smell only when the fan is running, it sounds like the motor is overheating. The fan is buried in the dash on the drivers side.

Are the elbows that carry air from the HVAC filters to the firewall sealing tight on the firewall?
 

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Discussion Starter #6
When you say "heater on" do you mean the fan? If you get the smell only when the fan is running, it sounds like the motor is overheating. The fan is buried in the dash on the drivers side.

Are the elbows that carry air from the HVAC filters to the firewall sealing tight on the firewall?

Sealing tight = No. Definitely not.

Heater On = Yes, fan is running and pushing heat instead of AC. Never had an issue with the AC running since I bought the car.
 

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If you have the defrost button pushed you have heat and AC on. The car uses the AC function to dry the air. You will only feel heat but if you check under the hood you should see the AC clutch cycling.
 

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Discussion Starter #9
Does it smell like coolant at all?
Nope.

If you have the defrost button pushed you have heat and AC on. The car uses the AC function to dry the air. You will only feel heat but if you check under the hood you should see the AC clutch cycling.
Thanks for the clarification on that Sailor. AC alone seems to work fine.
 

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I would be guessing that the fan is drawing a smell that is always there in. Next time at the track, when the fan is not running pop the hood as soon as you are in and take a wiff. I think you need to do a full inspection or try somethings IE put the blower on def on your way to work and see if you get the smell. Take it for a blast on the highway but at high rpm then pull over pop the hood. Maybe pull the side covers off the HVAC system and have a look with an inspection mirror. Might be a piece of plastic stuck in the core. Would not be the first time a flap has fallen off and stuck itself in the heater core.
 

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Discussion Starter #11
I would be guessing that the fan is drawing a smell that is always there in. Next time at the track, when the fan is not running pop the hood as soon as you are in and take a wiff. I think you need to do a full inspection or try somethings IE put the blower on def on your way to work and see if you get the smell. Take it for a blast on the highway but at high rpm then pull over pop the hood. Maybe pull the side covers off the HVAC system and have a look with an inspection mirror. Might be a piece of plastic stuck in the core. Would not be the first time a flap has fallen off and stuck itself in the heater core.

Coincidentally, drove the car to work today and got the smell. Granted, I was driving in a fairly spirited manner but not like the track. Heater was on about half way in terms of fan speed.

Will drive home in a gingerly fashion tonight with the heater off for 8 miles and see if I get the smell. Then I will drive for the next 8 miles with the heater on and see if it comes back.

I suspect you are right, Sailor. Probably some of the crumbled plastic down in the heater core.
 
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