Annual Sill and Rocker Panel Rustproofing Thread & Poll

It’s getting to be that time of year again so I thought I would ask a few rocker panel rustproofing questions that I have been pondering for a while.

1) Does anyone who has used Penetrol in their rockers have any updates on how effective it has been? And how did you apply it, garden sprayer?

2) For anyone who has bought the Moss Waxoyl kit, it seems like $50 for their special pump is kind of expensive, do you think it would work with a hardware store pump or garden sprayer?

3) If I apply Penetrol, Fluid Film, or Waxoyl can I then apply a different product over it next year or am I pretty much committing to use that same product every time?

4) Does anyone have any photos of exactly where they drilled the holes used to access to the rockers? Did you drill holes in both the front and back, and what about the doglegs?

Just for fun let's add a poll about what rustproofing product is the most popular.

Fluid Film. It's on the shelf, it sticks reasonably well, and I don't drive in any sort of rain that would wash it off.

I used various methods with Penetrol. Some areas with a garden sprayer, some areas a brush, and some areas a rag with the end of a long piece of Romex wire wrapped around it.

If you do a thorough job with Penetrol, I don't see any reason why you should have to redo it for at least a decade or so. It's a varnish-like coating that dries very tough.

$10 for Penetrol. If I ever do it again I won't bother with the sprayer, but if you do use one the small ones are less than $10 at Walmart.

When my front fenders were off I cut a flap of metal in the rocker. I used the Romex and rag to swab the rockers all the way back. Removed the upholstered panels behind the doglegs and used the garden sprayer there, until it ran out the bottom.

I asked the same question about the holes, and got little to no responses. I did a lot of my resto using Penetrol. I bought some el cheapo spray bottles/doz at Homo Depot. They get into a lot of spots and just throw them away when they tack up. I used a garden sprayer, but it is a real bear and a PITA to clean up. I bought a SS steel undercoating sprayer kit from ??? brain fart??? eastwood!!!!! and it works like a charm. The wands will go any where and they sell a drill bit with plugs to get into the tough areas. Clean up is a snap. I got the upper dog legs with the spray bottle and the tight spots with the eastwood undercoater. I am getting ready to drill the sills and frame for the same treatment. Good luck. David.

Have been meaning to do some rustproofing myself but have'nt been able to because its been very wet round here recently and i didn'nt want to trap any moisture under the waxoyl.
Having just read a little bit into how penetrol works, am I right in thinking this should be alright to use (in damp conditions) as it gets underneath the water and forces it out. or have i understood this wrong?
thanks.

I'm not saying Penetrol absolutely won't work over moisture, but I think it would be much more effective over a dry surface, as well as one with as little loose rust as possible.

my kingdom for a garage.

I honestly think there is no hope. Unless you keep out of the salt, the car will rust out. Poor MG's just have no resistance to body corrosion. I have used a bunch of these rust-proofing methods, and they all attract too much dirt, which leads to moisture, then rust. I just try to use good paint coatings, make sure all my drain holes are free, and I make sure I do not get dirt build up in any of the confined spaces. I have been known to drill extra drain holes to make sure I have good air circulation to dry up moisture.

The cars that didn't rust out, are the ones that had open bottom rockers like the Mercedes Benz 220S. Dirt was washed away, and moisture was allowed to dissipate.

Penetrol. It dries rock hard and does not collect dirt. Plus it goes on easy and seeps everywhere.

how different is Dinitrol from Penetrol??

When I restore a car I wash out the rockers with a pressure washer and then let it dry about a week in my basement. I then pull it outside and fill the rockers with penitrol and rotate the car making sure every thing is coated. I then coat everything under the car with POR 15 and then prime with an epoxy primer and paint with the same paint that I paint the exterior of the car. The only drawback is when I forget to put some cardboard under the car to catch the excess penitrol that drains out of the rockers.

I'm repairing my doglegs at the moment and so have access down through the inside of the rockers. I had read on the POR15 page that a spunge on a stick was a technique that was used to coat the inside of tailpipes. I was planning on coating the inside of my rockers with POR15 using this technique. What are your thoughts to that?
Thanks

Penetrol and an old plastic spray bottle (throw away.)

Robert, I don't think you can coat everything inside the rockers with the POR. you will have areas that are coated and other areas that are not coated. That is the reason I use penitrol. I use a garden sprayer with a flexible wand where I can coat everything inside the rockers. When I do mine I have the car on a rotator which makes it easier. I fill the rockers as full as I can and rotate the car where everything is coated. I generally use about a gallon of Penitrol per car. Of course a lot of this drains back out but I know that everything is coated.

Holes for rust proofing. OK. Sorry only one photo, but I'm not sure the rest of the areas are necessary.

1) One in each of the small closing panels at the rear of the rocker boxes (front of the rear wheel wells). See photo as to where. This hole allows you to snake a long tube or hose for spraying all the way to the front of the rocker box on its outward side (side to the outside of the inner diaphram panel). I use a nozzle that sprays 360 and pull back slowly as the fluid (your choice) is applied. A plastic plug inserted when done with seam sealer or silicone seal on it. This area gets a lot of road wash, so the better the seal, the longer your dog leg sections will last.

2) One at each end of the top of the inner rocker box section (on the IN side of the diaphram and one in the center. These holes are made on the top of the door sill so that a small hose can be inserted into these areas (aiming both forward and backward). When done, the holes are capped with plastic plugs, and the top of the door sill recovered with the Rubber or carpet sill covering.

3) The area between the actual fender skin (the part you actually see exposed) at the rear dogleg can be effectively treated by removing the interior trim panel, and spraying between the fender skin and the interior portion (rear of) the exterior rocker panel which the fender covers up. Fluids will drain out the bottom, and that is not a bad thing.

4) The area between the actual front fender skin and the forward extension of the outer rocker panel can be treated both from the rear (at the forward door opening where the hinges reside, and by drilling a hole in the closing panel at the rear of the front wheel well. This area is similar to the dogleg area in that dust will accumulate between the fender skin and the rocker panel, trapping moisture. It is best to lay the preventatives on thick here as it is not easy to get to or to seal 100%.

5) Forward frame member box sections. Generally pretty well sealed as is, but you can drill holes and spray in much the same way as for #1 above.

6) The crossmember under floor. There are already holes in these and they are usually great sand, silt, and roadwash traps, because most POs never paid them much mind. When I replaced my floor pans, I rebuilt these as necessary (had to replace the driver's side half), removed crap and rust to bare metal and then used Marine epoxy (POR-15 would have been as good or better) inside before closing with the floor pans. Afterwards, sprayed heavily with preventative, and then seam sealed the cross member to the pans and plugged every opening either with plugs or seam sealer (as required). Leaking oil does not prove to be that good a rust preventative INSIDE of the crossmember, altho you can be fooled by looking at the oily outside.

7) The gap between the underside of the fender (on top) and the top of the "Trumpet section" (that oddly shaped box section over the wheel arch in the front wheel well). This area simply collects debris over time, and altho exposed to drying air, the usual accumulation of silt and debris does a remarkably good job of holding moisture for longer than you'd like and causing rust ~ both on top of the Trumpet section and, if enough crap has accumulated, the underside of the front fender. Mostly, all you can do here short of pulling the fender, is to clean away as much accumulation as possible, possibly paint it (POR-15 comes to mind), spray with preventative, and then wash the area out at least once a year.

As a general rule, anywhere you see silt and crap collecting under or outside on your car is a potential candidate for eventual rust. Sweep them clean, spray with whatever, and pay attention to these areas when you find yourself in the area.