Replace trunk floor?

[Tom in seattle]

I have discovered a pinhole size rust-through in the floor panel of my 250sl.  The floor otherwise appears firm.  Is  replacement metal available?
But I’m not sure the best solution is maybe to coat it with Fiberglas ( no mat) and paint.  This minor flaw surprises me and appears the result  of water dripping into the trunk from the folding top boot.
What advice would you give?

[johnk]

Is this on the left side? K&K Manufacturing has a replacement for the entire center panel for about $200. Most cars just rust on the left side of this panel. Instead of replacing the entire center panel some of us have cut off the left 12 to 18 inches and replaced just that portion of the center panel. Its about 1/4th the work and yours does not appear that bad.

I would never put fiberglass over rust. It doesn't serve any purpose, it can trap in moisture and cause more rust, and will lower the value of your car. Not sure I could recommend anythng but replacing the metal on cars as valuable as ours.

[doitwright]

If the hole is as small as you say, a little welding and grinding will take less effort than replacing sections. Most good body men prefer to replace just the deteriorated sheet metal and only go for a replacement panel if fabrication time is not worth doing by hand. I had to buy the right side of my trunk floor. The part that fits under the Jack support. It had several pin holes but the depressed grooves in the metal would have taken too long to make so we just bought that part from K&K. We bought some pieces for the rear quarter panels and everything fit together just fine. My body guys said they fit much better than what they are used to getting with aftermarket parts for US made cars.

[Pawel66]

One observation as for th epotential cause of presence of water in the trunk: I noticed that even during washing the car, water may get in through (in my caase) 280SL, Automatic and the star. They need to be properly sealed. I overlooked it initially and then I was surprised - where do I get water from after washing the car.

[Shvegel]

For some reason the new floor from Mercedes is thinner than the original one.  I would definately patch the floor before replacing the entire thing.

[doitwright]

For some reason the new floor from Mercedes is thinner than the original one.  I would definately patch the floor before replacing the entire thing.

Thinner than the original? And the original was already too thin.

[Scottcorvette]

Never noticed any real problem with a difference in metal thickness when I cam to do mine, and I was joining a late floor to an early floor. For what its worth the two panels married up very nicely and I though the replacement a good panel. Its no mean feat though and not to be entered into lightly, at least it wasn't for me!

I would have a good poke around in there if it were me. It has been my experience so far on mine that one pin hole is being kept company by a few others once you start to dig. If it is just one pin hole and maybe a bit of pitting POR15 make a pretty good repair putty and a sort of urethane paint that goes over it. I used that on a GTO I had on the trunk floor and it worked well.

Fiberglass is a definite no-no though, not good on a steel car.

[laurie]

A little late picking up on this problem, maybe too late to help you Tom, but for others in the same bind here's my penny worth.
First the gas tank should be removed before any attempt to repair, weld or replace.
I bought a replacement, center floor panel and cut out the rotted one.
It seemed to me condensation between the gas tank and under side of the floor contributed greatly to the rot.
After removing the panel I used a nibbler and disc grinder to remove any bits left over around the perimeter frame.
The new panel fitted nicely enabling me to spot weld it in, after which I sealed inside and out side edges with black polyurethane caulk, working it into the join.
Prior to installing the gas tank I sprayed a few coats of truck bed coating on the tank and underneath the new panel and fitted new insulation pads.
(40 years of owning and summer running a 230SL)
Laurie.