False floor/bottom in rear trunk

TomasL

TomasL

True Classic
In my rear trunk there is a false floor/bottom, that I needed to remove in order to gain axess to the bottom screws in the inspection/axess hatch to the engine bay.
I was a piece of sheet metal screwed in.
Is that supposed to be there or is it something a previous owner fitted?
 
TomasL said:
Is that supposed to be there or is it something a previous owner fitted?
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If this is what you are referring to it is a factory item. Should be a few inches of insulation under it to keep the trunk floor heat from the exhaust at bay. Once you remove the panel, take a quick peek under the insulation as that trunk floor is notorious for tin worm.

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TomasL said:
Yepp, no insulation, as far as I can recall
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If the car is not your daily driver, then you are better off without the insulation IMHO. I don't even have the tray in my 85x. I never reinstalled it after the car was painted. My 85 also lacks a cat, so that reduces the heat under that area.
 
The early cars without the engine compartment access panel don't suffer so much from rust in the smuggler's compartment.
 
The early cars didn't have the engine compartment access panel so it's very difficult for the water to get in there.

That engine compartment access panel is an invitation to water to meet the fiberglass insulation in the smugglers compartment - if you drive the car in the rain - because it's not sealed up. That panel is fitted to the trunk side, so water gets in when you drive your car in the rain.

I suppose you could put something in the truck that leaks into the trunk, like a bottle of water, or maybe a cooler? Any idea how the water got into yours NEG?
 
MikeHynes said:
Any idea how the water got into yours NEG?
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I'm not picking on you Mike, just offering answers to the question. In the case of my '79 there are also other possibilities for water leaking into the trunk, aside from the rotted weather seal. Through the four holes the dealer drilled into the lid when they installed a chrome luggage rack, without any seals. Or the huge hole drilled through the lid for the old school mobile phone antenna. Or the age rotted/shrunken "Fiat" emblem mounting grommets. Or the two rust holes on either side at the rear corners behind the wheel wells. Or the body seams around the trunk area that never got properly sealed at the factory. Or the miscellaneous screw holes for mounting various components like the carb fan, smog solenoids, etc. And then there is the rot from below where the exhaust heat baked all of the finish off the sheet metal and it rusted through into the space between the two trunk floor panels. Oddly enough, that service access panel between the trunk and engine bay had some sealant around it that looked 'factory' to me. Not that it sealed any better than all the other so called "seals". But my point is I think water gets in from all over. ;)
 
I’m not sure, mine has new seals when I bought it, the Emblem badge is a prime suspect as Jeff says. The seals would have to be disintegrating to actually leak afaik, also the hidden floor has holes in it factory fitted, moisture laden air can easily get between the layers with the insulation keeping it there along with condensation especially over here in the wet UK. My 1500 with the access panel had no such issue but then it was 10 years younger
 
Going to a rigid insulation which doesn’t absorb and hold water would be worth changing to, reflective rigid urethane foam insulation would work well here. Do not use polystyrene insulation as its melting point is quite low. Urethane insulation is not a thermo plastic, it is a thermoset material so can deal with the reality of the heat in that part of the car. It is also a closed cell foam so it won’t hold water either.

The other reason it rusts out under there is the insulation below it holds water (it is fiberglass and it holds water very well) against the steel which along with heat makes a dandy environment for rust propagation. That insulation could be replaced with rock wool which doesn’t hold water and rejects it.
 
I wouldnt use rock wool since it can hold tremendeus of water (you use it in hydroponic growing as well, just because it adsorbs water)
Some heat resistant closed cell insulation is the best I think.
 
Sorry, way off topic. But these posts just reminded me of a test question on the medical board exams way back when. It pertained to something involving chemistry and biology and utilized the word "adsorb" (as opposed to "absorb"). Frankly I wasn't aware of the distinction and in the hurry to get through the long difficult exam I paid no attention to the spelling. Unfortunately it changed the whole meaning of the question and almost everyone got it wrong. Funny what still sticks in our minds so many years later, yet I can't remember important stuff for more than a few minutes. :rolleyes:
 
Question is, how hot does it get?
you could allways mount an heat shield above the silencer, and reduse the radiated heat.
 
The early cars have issues too. I've done 3 floors in California cars (all '74s). None showed issues with water intrusion and they were relatively rust free in all the other usual areas including the corner pockets. I think the heat cycling and humidity levels have something to do with it on some cars. My '75 came out of a very wet environment and was stored outdoors for several years. The lower floor was very clean and the insulation had no telltale signs of being wet at some point, but you can see where the heat has blistered the finish. Luckily caught in time, it would have progressed into rot at some point. I have never replaced the insulation with anything other than high temp tunnel shield on the bottom of the drop in tray, and the same underneath over the top of the exhaust assembly.

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