Body: Undercoating Removal, Part II

Today I finished scraping the undercoating off the underside of the body. Last weekend I completed the front section of the underside. This week I tried to spend one hour each night doing some scraping, and today I polished off the rear of the car. This is tedious work, though not that physically demanding.

Mid-week my heat-gun from Harborfreight ($19) broke down, so I exchanged it for a new one under their 90-day waranty. In general I try to buy high quality power tools, but if I can save some money on a tool I’ll use on a very limited basis I will buy from Harborfreight.

During last week I tried to spend one hour per evening after work scraping away at the undercoating. This enabled me to break-up the tedium into more tolerable increments. I made decent progress, completing the area directly beneath the rear shelf over a three-day period, as well as one of the rear wheel wells.

This morning I removed the undercoating from under the passenger side rear wheel well. This area was pretty tricky to do because it is difficult to reach and also has a nearly continuous curve that makes scraping with a flat-edged scraper difficult. I started on the front lower edge.

I applied heat by holding my heat gun, set on high, about two inches from the surface for ten seconds. That softened the tar enough that I could scrape down to the metal.

I worked my way up the front edge and around the apex of the wheel well towards the rear.

After removing the undercoating the seam in the middle of the wheel well was visible.

That left the remaining area under the trunk to be scraped.

On the underside of the trunk I began on the left side and worked my way across.

I also scraped the tar off the underside of the rear fenders.

Here is the completed trunk area.

This completed the undercoating removal. It was a long job that would test anyone’s patience, but necessary to reveal the condition of the underlying sheet metal. Here is a shot of the exposed underbelly of the body and the pile of tar chips I removed.

Body: Undercoating Removal, Part I

This weekend I spent several hours removing the tar undercoating from the underside of the body. The tar coating was originally applied to the bare metal; I am removing it to see if/how much rust damage there is. The coating serves to cushion the body from stones and other road items that may contact the metal. It also insulates the inside of the car from heat and noise. For this reason I will most likely replace the coating with a modern version after treating any rust and applying a rust preventative to the sheet metal. But first I had to get down to the bare metal.

To remove the coating I used my heat gun and a metal scraper to do most of the work. On my scraping hand I learned to wear a thick work glove to protect my skin from molten tar. This is not particularly difficult physical work, but it is tedious and takes time and patience. Anyway, after spending several hours on it I am probably around halfway done.

I started with the areas underneath the front fenders, which were coated in the material. I applied my heat gun a couple of inches from the surface, allowing around ten seconds for the material to soften. Then I scraped down to the metal.

The very front end of the rocker panel (also covered by the front fenders) had a thick coating on it as well, where there was no rust. I scraped it off in a similar manner. So far this area, along with the lower edges of the fenders, has been the most rusty on the car.

Next I moved on to the outside of the engine bay area. More heating, more scraping.

Here are some shots of the under-fender area after the bulk of the coating was removed. There remained some tar residue on the bare metal, which I will address later.

Next I addressed the lower portion of the firewall opposite of the footwells. More heat.

More scraping, and the material came off.

Then I moved under the body, starting on the driver’s side.

First I cleaned the inside of the rocker panel up the length of the car, then I moved up the underside of the body. I found it easier to scrape front-to-back over the ridges in the metal in order to more effectively remove the coating from the elevated and recessed areas.

Here is how it looked after I completed the passenger side, leaving only the transmission tunnel coated.

Next I went to work on the transmission tunnel. The odd shapes and reinforcement brackets in the tunnel made it difficult to scrape, but eventually I finished it.

After spending around five hours of total work time, working intermittently, I had the front portion of the tub complete. I have become proficient at perching underneath the body and reaching upwards with the heat gun in one and and the scraper in the other.

The rear quarters, trunk area, and wheel wells remain. They will be tricky because, unlike the front end, they consist of many small angular surfaces which are harder to clean-up than large, relatively flat ones.

Body: Floorpan Undercoating Removal

Today I removed the tar undercoating material from the tops of the floorpans. This material is supposed to act as an insulator for sound and heat. It was applied to the bare metal by Nissan prior to painting. I want to get under there as part of my process of fully stripping the body in order to find and neutralize rust.

The two most popular way to remove this stuff are (1) using a heat gun to soften it and then scrape it off and (2) using dry ice to freeze it so it becomes brittle enough to shatter-off. Having used the former method I would highly suggest that anyone else use the latter. It would have probably been faster and less messy to use the dry ice.

Here are a couple of pictures of the undercoating, which was in two sections (front and rear) on each side of the cabin. I began with the rear section on the passenger side. I applied heat to the corner with my Harborfreight heat gun.

When the material started to bubble on the surface, I used a metal scraper to lift it at the corner. I pushed underneath, scraping up the material and moving the heat gun to stay ahead of the scraper.

I opened up both garage doors because the smell was pretty strong. I worked my way across the front edge, and then back along the door opening.

Next I worked across the panels and up the opposite side (front to back) along the transmission tunnel. Then I scraped all in between to remove the bulk of the material.

Then I turned my attention to the front section of undercoating on the passenger side. I started on the floor.

Then I moved up the firewall using the same scraping procedures. It took around 90 minutes to complete the passenger side.

Next I did the driver’s side, which took about another hour.

After the scraping was completed, I moved the body outside. There was still a lot of tar residue remaining on the floorpans because the scraping just removes the bulk of the material. I used a tar-removing solvent known as “Goof Off” to remove the residual tar.

The solvent has some fairly awful fumes and can be tough on skin, so I used my heavy stripping gloves. I poured a bit of the solvent onto the floorpans and then agitated it with my scrub-brush, as recommended in the product instructions.

Then I wiped the residue off using a clean rag. The solvent did an effective job of loosening the remaining tar from the metal but I had to physically remove it by wiping. The solvent was oil-based but tends to evaporate fairly quickly, so it was important to remove the material quickly.

I used the same method on the other side of the car. In no time the bare metal floorpans were exposed. The verdict is good, at least from the top: there is minimal rust around the drainage holes only and the floorpans are largely solid. Here are before and after shots:

The solvent I used was pretty nasty stuff, although effective. For this reason I would recommend trying the dry ice method.

While I was working with the solvent I decided to remove the remaining horsehair padding stuck on the top of the front wheel wells. I applied some Goof Off and then scrubbed the hair and adhesive with my scrub-brush.

That got them pretty clean. I applied a bit more solvent and used a scouring pad to remove any remaining adhesive from the rear shelf and side areas, as well as the wheel wells themselves.

Then I used a wet rag to wipe away any remaining solvent.

Detailing the Engine: Valve & Timing Cover

Today I spent some time stripping and cleaning the valve cover in preparation for polishing it. I also cleaned-up the aluminum timing cover for the same reason.

I removed the valve cover first. It was held in place by two cap nuts, which I removed using a 15/16″ socket. I then removed the washers underneath the nuts.

Next I removed the oil cap.

Then I pulled the valve cover off and then removed the rubber gasket from the valve cover.

I covered up the exposed head with some aluminum foil to keep out dust, rodents, etc. But first some gratuitous head shots:

I removed the small triangular vent cap by first unbolt the three nuts that held it in place using a 10 mm socket.

Someone previously painted this valve cover a tomato red color. Originally the U20 valve covers came in bare aluminum. I intended to return a more stock appearance to the cover by stripping off the paint and then cleaning and attempting to polish the aluminum cover so it will be shiny. I set-up my work area outside for stripping the paint. I used more Kleen-Strip, which I had previously used for stripping the intake manifold and carburetor heat shield. I began to apply the stripper in one heavy coat using a cheap paintbrush. As the instructions stated, I avoided going back over stripper I’d already applied in order to maintain its seal against the paint.

I coated the entire valve cover in a thick layer of paint stripper. Because it was a fairly warm day (>80 degrees), I covered the stripper with a layer of plastic wrap to prevent it from drying out before it had a chance to work on the paint.

I peeled off the plastic wrap after 30 minutes. The Kleen Strip really worked well–after one application the paint was bubbling off the surface of the valve cover.

I scraped the red paint off using my plastic paint-scraping tools to avoid damaging the aluminum.

I then applied a second coat of stripper to those areas where the paint remained. After allowing it 30 more minutes to work I used a scouring pad to scrub at the painted areas.

After the majority of the paint was removed I sprayed down the valve cover to neutralize the paint stripper. Then I sprayed on some Simple Green to clean the piece.

I scrubbed the valve cover with another scouring pad and then rinsed off the cleaning solution.

The next step was to begin the polishing process on the valve cover. For this I sanded the piece using 320 grit, 400 grit, 600 grit, 1,000 grit, and 1,200 grit sandpapers. Since I was wetsanding, it was very important to continually spray the part as I was sanding to rinse away the fine particles coming off, otherwise the sandpaper could become clogged and become ineffective. For this reason I used my parts washer, with plain water, to continually spray water on the part to keep it clean.

After several hours of sanding with progressively finer grits of sandpaper the valve cover was becoming cleaner and more shiny.

Then I went to work on the timing cover on the engine. I removed the front inspection cover first. I used 10 mm and 12 mm sockets to remove the bolts holding it to the head.

Then I removed the cover and pulled the gasket off the inner edge. I will replace this gasket when I reinstall the inspection cover.

Then I removed the water pump from the timing cover. Initially I wasn’t planning to replace the water pump, but the shaft where the pulley mounts is fairly rusty and I’d rather replace it now while the engine is out of the car. I unbolted the water pump bolts using 12 mm and 13 mm sockets.

I removed the water pump, which I will replace.

I made a plug out of a ball of masking tape to stuff into the water inlet hole to prevent any water or dirt from getting inside.

Underneath the water pump was an area I was unable to access to clean before the pump was removed. I sprayed this area, scrubbed, and rinsed it clean.

Then I wetsanded the timing cover, continually spraying it with water to rinse away the dirt coming off. After working through all of the grits (320, 400, 600, 1,000, and 1,200), the timing cover was fairly shiny.