Rear Bumper Clean-up

On the drive to the coast for the family gathering for Independence Day, I realized that something in the drive-train was leaking oil.  Drips would hit the air turbulence under the bus, atomize, and the resulting mist would get caught in the vacuum behind the moving bus.  Within the vacuum, it would splatter against the rear of the bus; especially the rear bumper.  Over the last few posts, I explained how I solved the leaking oil (it was a bad input shaft seal, damaged by a faulty oil slinger, which was either damaged because I didn't have a pilot bearing in my flywheel or because AA transaxle used an old bell-housing).  Now that the oil leak is solved, I can focus on the last thing I wanted done before the Fall (see Setting and Re-setting Expectations): cleaned up and painted rear bumper.  Today's post covers the start of that journey.

The Missing and the Modesty Skirt

scrub clean first

Like the bolts holding the front bumper on, the square-lock bolts holding the rear bumper are in pretty bad shape.  Rusty.  Painted over with what looks like interior paint.  Missing.  I'll need at least 3 replacements when I'm all done.  At some point during the engine swap project, I removed the splash pans from either end of the rear bumper.  I'm sure that was a good idea at the time, and it gave me the opportunity to troll through my garage looking for them in my boxes of parts.  Like a trip down memory lane, it took longer than it should have, but I found them.  I set them aside and removed the modesty skirt from the bottom of the bumper.  I don't know why the bus has one of these; and I don't see any on the handful of buses I regularly see.  Maybe 1972 was an especially shy year for cars.  Anyway, I hammered it semi-straight-ish.  Then, I taped the front, bottom and sides and put it with the splash pans.  On a sunny day, I spray painted the pans and the unmasked front of the modesty skirt with rubberized undercoating.  Once dry, I removed the tape from the modesty skirt so rest of it could be painted white like the main bumper.

Sanding and Banging
Unlike the front bumper which had 3 distinct pieces, the rear bumper is a long stretch of curved steel.  The curves run top to bottom as well as curl in on the ends.  This made banging it straight more challenging.  Again, like with the front bumper, I aimed for 'good enough for camping kwality' in my bodywork.  Unlike the front bumper, the rear had a couple of very old bumper stickers on it and when they were removed, they took a couple coats of crappy paint with them.  This led to some unwelcome contours I tried to solve with 150-grit sand paper.  I learned along the way that the sand paper could help me identify minor dings by bringing up a lower level of paint around an area.  It was with this technique that I discovered that the bolt holes were centered on dimples the size of US quarters.  Some more banging with the hammer got them flat.

Paint, Wet Sand

undercoated

Once I declared "good enough" on the cyclical sand, hammer, sand process, I pulled out the white Rustoleum I used on the front bumper.  It's been about a year since I did that front bumper, so its time to review how it is holding up.  To be fair, the bus hasn't seen many miles (probably less than a thousand) since it was done, but it has been outside in my driveway where the kids are playing when it wasn't driving to music festivals.  The bumper looks good, and I mean really good.  No rust staining, no blemishes, no cracks or chips.  I applied straight Rustoleum with a foam brush inside and out and set it to dry.  The next morning, it was totally dry.  Total drying time was over 12 hours, but some ranters on the interweb claim it takes forever for this paint to dry.  False.  Just apply it properly: spread a thin coat always keeping a wet edge by brushing into the already painted surface.

Spackle?
After the paint set up, I could see large sections where the paint underneath had been pulled away by bumper stickers.  In a real body shop, they'd probably strip the whole bumper down.  I thought about that.  In a cheap-o body shop, they'd fill with Bondo.  I thought I could experiment with spackle, since that was what I had, and see how it behaves over time.  Worst case, it looks like crap and I strip the bumper down later.  Big deal.  First, I wet-sanded the paint.  I needed to do it anyway, and I figured that would give some teeth for the spackle.  So, with a basic putty knife and a small tub of spackle, I smeared paste over the bigger spots, and some small ones.  I slipped inside and watched some football for a couple hours while it dried and then cuffed the spackle down with 150-grit sandpaper.

More Paint
Once smooth, I wiped the bumper down with a damp paper towel and applied a second coat of white Rustoleum.  Same method, similar results.  This time, though, you could tell where the spackle spots were because the white paint wasn't shiny in those spots.  At this point, I figured I probably should have done something else, but I just plowed ahead: wet sand with 320 grit, another coat of paint, more 320 grit wet sanding.  This time, you really can't tell where the spackle is, but I wasn't 100% sold.  SO, I decided to wait a week and look again next weekend to see if another coat of paint would be needed, would help, or if I'd just be throwing product at a bad idea.