Smelly '84 240D - how to remove?

Hi Experts,
The interior of this old car is really smelly - like decomposing plastic -, especially if I keep the doors and windows closed.
I tried a large dish of baking soda in it for a week, with everything
closed, but there was no change.
I have heard of zeolite crystals that can adsorb odors on the surface and can release them when exposed to the sun, allowing the crystals to be re-used. Has anyone tried this, or any other solution, with success?
TIA
RF
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Odd that 23 year old plastic would be off gassing. Suggest you pull up the floor mats to see if a rain leak isn't the cause of the problem. Sunroof drains may have rusted out by now to cause such a leak.
--
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-->> T.G. Lambach <<-- wrote:

Thanks TGL.
Something is outgassing. The car is garaged most of the time and not very often is exposed to rain. I live in northern California where there is little or no rain between May and November. I take it out typically once a week and I pick the dry days. It has not been exposed to rain for at least six months. I'll remove the mats for a while to see if they are causing the odor.
RF
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Where are the sunroof drains located? I have a similar problem with my 84 300D that I know is letting water in to the rear passenger floorboard. It has filled up at least twice during summer thunderstorms, and I can't find the source. I thought it was the rear passenger door seal, but a trip to the car wash ruled that out (I think).
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The sunroof drain pipes start at the sunroof well and must go down the front and center pillars. The only way to know is to look and feed a wire into each to learn where each terminates. The get clogged with dirt and debris and eventually rust out.
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I live there too and know the conditions well. Two thoughts come to mind: a coolant leak from the heater core or battery acid corrosion that's pierced the firewall, behind the battery.
--
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