300TD Floorpan Repair: POR15 Floorpan Kit or Fiberglass?

[aaronkobi]

I recently discovered a few holes in the floorpan of my 300TD. The holes are surrounded by good metal, so it's a good candidate for repair (and not floorpan replacement).

Initially I purchased the POR15 floorpan repair kit, but I have been reading more about fiberglass mat/resin repair and thinking this may be stronger. Of course I would still treat the exposed metal with POR15 to keep rust from creeping back, but does anybody have opinions on the POR patch system as opposed to fiberglass mat and resin? They supply mat/mesh as well, but it seems they provide putty in place of resin.

Thoughts? Opinions? Thanks!

[Stoney]

The "putty" is actually the same thing that the paint is made from but in an unthinned version. It comes in a tube, fills cracked open seams and holes up to 1/4" dia and in 24 hrs sets to the equivalent of concrete.

When I made repairs to a Volvo trunk, I wire wheeled the surface around the hole to bright, painted with Metal Ready/Metal Prep and then used the POR Putty then scuffed the surface of the hardened putty and painted the entire area with POR 15 paint (both sides) and then reundercoated and had no problems after.

Now the area was NOT "structural" in nature. If I was doing a floor pan or any area that was supporting a seat track or the like, I would use something different than Fiberglass and Resin. If the area requires structural reinforcement, I wiuld use steel channel (10 ga type used for Exterior wall systems in new houses) and use the flange section of the channel, cut down with agrinder and prepainted with POR 15. Attach by riveting (SS Aircraft type rivets with a layert of POR Putty as sealant around the rivet holes and between the contact areas) and then fill the holes with POR and or Fiberglass from top side and then coat the underside with POR Putty and then a coat of POR 15 paint.

But first assess the extent of the corrosion. Remove as much undercoat as you can and do a test of the metal to see is it is rusted/corroded. At that time decide if the job is worth a local repair procedure or calls for replacement of the whole area with same part from a clean donor car.

If you cannot find a donor, I suggest going to a junkyard with a battery sawzall or grinder and cut oversize repair panels from the roofs of same age sedans or wagons and the cut repair pieces from that.

[Dee8go]

These were 1/4" and smaller holes, Stoney?

[aaronkobi]

Thanks Stoney. On an area of rot around the passenger side seat bracket, I plan on welding a bar of steel to bridge the gap between clean metal. I'm going to then bolt a 2nd bar UNDERNEATH the floorpan to create a rock-solid bridge of metal where the hole is. I purchased a new seat bracket from mercedes and will weld this to the steel "bridge" that I've created.

Once the structural reinforcement is complete, I'll prep and drown everything in POR15 and then either lay fiberglass or use the POR repair mesh to coat the entire area of damage. Here's the repair kit that I bought:

http://www.por15.com/prodinfo.asp?grp=FPTRK&dept=11

I really want to take care of this once and for all. Before even starting the floorpan repairs, I've been replacing all weatherstripping and clearing drains to make sure the inside of the car stays bone dry.

[Stoney]

1/4" and smaller one treatment will fix it. Larger needs two treatments with the first around the edges to reduce the hole to 1/4 in or smaller. the stuff sets up best in humid environment (it is a moisture cured urethane product).

Originally Posted by Dee8go

These were 1/4" and smaller holes, Stoney?

[Chad300tdt]

I repaired the rear driver floor in my wagon. I cleaned everything up and treated with POR-15 and then glued in some sheetmetal using JB-Weld. I used the POR-15 floorpan repair kit with the fiber sheets and put a layer over the top and bottom. I sealed that with the chassis black and then undercoating. It wasn't near the seat mounts for me so this has been holding up great so far.

[Dee8go]

Where can you get POR-15 products? Do they typically sell those at Auto Zone and places like that?

[Chad300tdt]

Originally Posted by Dee8go

Where can you get POR-15 products? Do they typically sell those at Auto Zone and places like that?

I order them from their website:
http://www.por15.com/

They're based in NJ and it gets to me in PA in 2 days.

[Dee8go]

Thanks. I don't need any yet (I hope), but I like to file stuff like that away. I'm sure i wall.

[Chad300tdt]

I just remembered ... do yourself a favor and use a fan to exhaust the interior while you do the floorpan repairs with POR-15. I used a vapor mask but didn't ventilate, and I got a thumping headache that lasted about 10 hours.

[Dee8go]

Thanks for the warning. I am wising up a little bit as I get older, too.

[asnowsquall]

Careful of rust near the rear of the floor, basically where the heels of peoples feet are when riding in the back. This area has bolts the go to support part of the rear suspension. If this needs restoration I would recommend welding in new metal. Shouldn't do cosmetic styled repairs here. Cut rust out and weld in metal.

[Dee8go]

That's a good point. Finding that out the hard way would be, . . . er, well, HARD.

[bob_98sr5]

aaron,

i had rust eat away some of my metal near the seat bolt area. i cut away all the rust, welded in new metal, and then treated (for good measure) it with POR15. read through my blog...i believe i did that in jan or february

the floor is structural since your mercedes is unibody---of course, a small fiberglass repaired hole probably wont compromise the integrity of your vehicle. The only places where i used the fiberglass repair product was in the wheel well and they were smallish holes.

bob