Need some undercoating advice, To undercoat or not to undercoat. Options

[FourBlades]

What have people used for undercoating their cars? Is undercoating a necessity
or is it optional? The car will be used for occasional street/AX/DE driving.

Should I strip the old undercoating from my wheel wells? It looks pretty stable.

So far I have cleaned the underside and painted with eastwood silver rust
encapsulator.



Thanks for any advice.

John

[charliew]

My experience with POR 15 is you HAVE to use their light blue Tie Coat primer to get anything to stick to either black or silver Por 15. I used it under the wheel wells and in the floorboards of a Jeep truck hunting wagon and the rubber under coat just fell off after about two years.
They say to top coat it while it is still tacky and maybe I waited too long to apply the undercoat.
I recently used the black on the bottom of a dune buggy pan and applied Gator Guard over it while it was tacky so this will be my last attempt if it comes loose.
On the jeep truck I tiecoated the complete front end with the front fenders off and it seems to be holding paint ok.
Undercoating will add weight but makes the car quieter and protects against rock chips but is a mess to take off if you need to remove it.
The area you did looks really nice and clean.
Por 15 rust encapsulator turns funny colors in the sun.

[Wilhelm]

I am in the process of stripping (sandblasting) my car to the bones and I think it must have won the "Let's see who can slather the most seamsealer into das Porsche?" contest at the factory. As I sand blast and dig out kilograms of seamsealer I am noticing rust especially on the bottom seams of the car where seam sealer has sealed in water and in area where the stuff is gobbed on under the wheel wells, especially the fender seams. My thought is that teeners collect water through open windows, leaking windscreens and worn out top seals. That water runs down hill and would leave the car in many instances except that goes through the metal seam only to be stopped by the externally applied seam sealer and is trapped in the vehicle. I'm thinking of primering all surfaces I can reach with epoxy primer then spray on bedliner on the inside floor of the trunks, floor of passenger compartment, gas tank compartment, and inside of the wheel arches in continuous panals so there is no edge for water to get under. I am also thinking of placing some self draining rubber valves (those soft thin wall floppy kind) in areas like the trunk or under the seats to help water exit. Basically as they say in the construction business I'm trying to think like a raindrop. Thought anyone????????????????????????????

[FourBlades]

I think you have a good point. 914s rust where water is trapped, either by
their design or by the foam and sealer Porsche added. My car was completely
rusted out on the lower 2 inches. The higher parts of the car look brand new.
Seems like insuring good drainage from all trouble spots is key.

I hate to put rubberized undercoat on my newly cleaned and painted
underside but it seems this is the only way to avoid paint chips and
subsequent rust.

[r_towle]

I am in the process of stripping (sandblasting) my car to the bones and I think it must have won the "Let's see who can slather the most seamsealer into das Porsche?" contest at the factory. As I sand blast and dig out kilograms of seamsealer I am noticing rust especially on the bottom seams of the car where seam sealer has sealed in water and in area where the stuff is gobbed on under the wheel wells, especially the fender seams. My thought is that teeners collect water through open windows, leaking windscreens and worn out top seals. That water runs down hill and would leave the car in many instances except that goes through the metal seam only to be stopped by the externally applied seam sealer and is trapped in the vehicle. I'm thinking of primering all surfaces I can reach with epoxy primer then spray on bedliner on the inside floor of the trunks, floor of passenger compartment, gas tank compartment, and inside of the wheel arches in continuous panals so there is no edge for water to get under. I am also thinking of placing some self draining rubber valves (those soft thin wall floppy kind) in areas like the trunk or under the seats to help water exit. Basically as they say in the construction business I'm trying to think like a raindrop. Thought anyone????????????????????????????

couple of thoughts, some if which I have heard from alot of the 356 guys.
First and foremost...the car is 35 plus years old now.
Be thankful they DID use some sort of undercoating or else it would have rusted more...
Water can and does run uphill, even more than you think in a car...its wicks up the seams into the car. Condensation forms inside closed cavities and gets trapped in seams that are/were bare metal...the best you can do is deprive the area of air and hopefull slow down the process of oxidization.

I would suggest you open up every joint, clean it out and reseal it for the next 35 years...use new chemicals, but dont rely just on piant...its to weak of a top layer for the underside of a car.

Wheel wells and the bottom of the car will see ALOT of dirt and never ever see you waxing or cleaning it...just a fact of life. Rocks chip paint...exposed paint will rust fast.

The one word of advice I got from a 356 guy was so to the point.
Once you are done restoring this car, it will never get restored again. It will be done (provided you do it right). It will never see the neglect it got in its first part of life because of the cars classic collectible nature.
It will live inside, it will get waxed, it will be kept ALOT cleaner than it ever was in the 70's 80's or 90's.....

So, whatever you choose to do will be cared for and kept in good condition...dont loose sleep over it...
If you put no undercoating and no seam sealer you are asking for a short life on the car. All cars need seam sealer, just do a good job and make sure the drain holes in the longs are kept open.

Rich

[beech4rd]

I'm not sure that bedliner is a good idea for the floors and trunk. My car came with bedliner material ( Rhino Liner) sprayed liberally on the floors and around the trunk. I removed it all and found tiny pools of water (and the beginnings of rust) at many of the seams and especially in the low points of the floors. I think that the exterior of the car should get the underseal and the interior should be seam sealed, epoxy primed and painted. Regular cleaning will allow you to check for any possible rust. Bedliner will conceal rust. I'm not sure about the tar based floor liners that were installed on the cars at the Karmann plant either- I've restored a Mk 1 VW Scirocco that was made the same way and I discovered rust when I removed the tar liners from that car, caused, I presumed, by rail/melted snow being brought into the car on shoe soles, wetting the carpets and eventually finding it's way to the metal floor. On both the 914 and the Scirocco, most of the floor rust seems to have started inside rather than outside the cars.
Chris

[Lou W]

I stripped mine down, primered and applied 3m body schutz. You can then cover it with a body color, leave it alone or shoot clear over it like I did. It's suppose to work real well against rocks and debris.

Rich, I think you made a very good point with what the 356 guys are saying about doing it right, "it'll never be restored again".