Rust Repair

Recently I have had two cars in the garage for rust repair, a Saab 900 and an MGB.

The interesting thing is, on each car the rust was caused by poor body work. Each car had plastic body filler repairing a dent. The body filler was applied to bare metal. At some point, the body filler cracked and moisture seeped in. Body filler does not stop water.

Water can creep down through the filler to the bare metal, and cause rust. On each car the metal behind the body filler had rusted away, leaving rust holes.

After I do the hammering and welding, I coat bare metal with epoxy primer BEFORE I apply any body filler. I also start with aluminum body filler first, then transition to traditional polyester body filler. Aluminum body filler does offer some resistance to moisture.

To fix these rust holes, I used a cut off wheel to cut out the rusted metal. Next, I traced the cut out piece on new sheet metal with a sharpie marker. I carefully cut the piece out, subtracting about 1/16” on each side. The new piece was carefully mig welded in, only welding about 1/4” at a time to prevent heat warpage. After the weld-ing is finished, the welds are ground flush and the metal is hammered flat. Next I apply a layer of epoxy primer, followed by a light skim coat of body filler.

 

Automotive Primers

1018 primer adMy last column discussed the evolution in paint technology. This month, I will talk about what is under the paint and talk about primers.

Automotive primers have come a long way in the last few decades. Primers serve several functions. First, they bond to and protect bare metal. Second, they fill very small imperfections. Third, they provide a stable base foundation for the top coat, or color paint.

Why are there so many types of primer? Not too long ago, primers were lacquer based. If the top coat was lacquer this was simply applied over the primer. If the top coat was an enamel paint, an enamel primer/sealer was applied over the lacquer primer. These primers were often unstable, and did little to protect metal from corrosion. Lacquer primers would shrink months or years after being sprayed, showing sanding marks and causing the top coat of paint to crack. Lacquer base primers do not shed water, they actually absorbed some moisture. This moisture would then find its way down to the bare metal. Of course, lacquer based paint will go back to a liquid when exposed to a solvent, like lacquer thinner.

auto paint sprayAcid etching primers did a good job of adhering to bare metal, but offered little corrosion protection.

Epoxy primers, or “2K” primers bond well to bare metal, and also offer excellent corrosion protection. Epoxy primers are not sandable, and do not work well as a primer surfacer.

Primer-surfacers are used for final body work to give a smooth, flat surface foundation for the top coat or color paint. These primers have filler in them, and are easily sandable. These are the primers that are laboriously block sanded until the surface is smooth and flat.

Once the block sanding is done the primer is sealed with a sealer primer.

Final paint will show color shift if painted over different color primers, and will also show any sanding marks. Color paint is only a pigment, and will not hide anything underneath.

Confused yet? Don’t be. There is a system to priming. You may remember about 20 years or so ago car ads talked about the multi layers of paint. As urethane paints began to dominate the automotive paints, these “multi-layer” paints became standard.

First, an epoxy, or catalyzed primer coats and seals bare metal. There may be a self etching or acid etching primer under the epoxy primer. Epoxy primer has exceptional adhesion and corrosion protection.

Over the epoxy primer is a primer surfacer. This primer is sanded smooth and flat. Over the primer surfacer is a sealer. The purpose of the sealer is to provide a thin, hard, smooth surface over the primers for the color coat. Without the sealer primer, sanding marks and color changes will show in the top coat of paint. Sealers need to be top coated relatively quickly for the color paint to bond well.

If the color coat is a base/clear system, then there are two additional layers of paint on top of the primers.

I am amazed at how well these new primers work. I have had excellent results with using epoxy primer for rust repair. The rust repair actually outlasts the factory corrosion protection. Two part catalyzed primer surfacers are easy to sand, and remain stable forever. No more sanding marks showing up months after a car is painted. I often use epoxy primer thinned with reducer as a sealer. It is a bit more expensive than sealer, but it is one less product to have on hand, and I have been very pleased with the results.

Automotive Paints

This month’s question comes from Wendell Nobel:

Dave, I would love to read a little dissertation on automotive paints. I recall a day when GM cars were all painted with acrylic lacquer and Fords were acrylic enamel. Now we have polyurethane base coat with clear coat, single stage urethane and even some water based stuff. What is an antique car guy to make of it all? Should we use what was on the car when new or get up to date? Will environmental laws make the question moot?

Let me first briefly explain the history of automotive paints. The early autos were painted with the same paint people had been painting carriages with for years. There was no “automotive” paint. Not paint in the traditional sense we think of when we talk about paint today. Early paint was basically linseed oil and a binder, with pigment, or crude shellac. This paint was applied with a brush and took a long time to dry. These paints were not very durable, often literally falling off the metal in a year or two. These finishes offered very little U/V protection and broke down quickly.

The biggest challenge with producing the Model T Ford and other early cars was the time and space needed to paint cars. The parts were laid out on the floor and took days to dry. This bottle neck in the production was a huge problem.

Nitrocellulose Lacquer paint was developed to alleviate the time/space problem. Nitrocellulose Lacquer paint is made from the nitration of cellulose plants (boiling down plant fibers and mixing with nitric acid). This is also how celluloid film was made. The solvents evaporate from the paint, leaving a glossy durable paint finish. These paints need to be “rubbed out” to produce a shine. This paint does not “cure” and will return to a liquid state when solvents are applied. A popular early nitrocellulose lacquer paint was DuPont “Duco” paint.

Nitrocellulose Lacquer dominated the automotive paint market from the early 1920s well in to the 1950’s when it was displaced by Acrylic Lacquer, a synthetic polymer acrylic resin based lacquer. Acrylic Lacquer dried quickly, however, still needed to be buffed to a high gloss.

Enamel paints used enamel resins. This type of paint takes much longer to dry than lacquer and actually dries in two steps. First, the enamel reducer evaporates and the paint becomes solid. Next, the resin oxidizes when it reacts to the air. This is why the new finish cannot be waxed for 30 days after application. The enamel paints dry to a hard, glossy finish and do not need the rubbing out as lacquer needs. The drying of enamel paints could be accelerated by the use of a baking oven.

Enamel paints required the need for clean spray booths. The paint took so much longer to dry than lacquer paints; the finish was much more susceptible to damage from debris before it dried.

Lacquer and enamel paints were much more durable than the paint they replaced, but still offered minimal protection against U/V light and corrosion.

Lacquer and enamel paints are very unstable, and begin a color shift almost immediately. This fact makes them very hard to color match. People go to great lengths to match original colors. Unfortunately, the reality is the “original” color was so unstable there really is no true original color. Two cars painted the same color at the same time would not match each other after a few years time.

Today’s urethane paints offer much more protection than the lacquer and enamel paints they replaced. Urethane paint cures in three steps: evaporation of the reducer, oxidation of the resin and an irreversible chemical reaction between the resin and the isocyanate catalyst. Urethane paints began to be widely used in the late 1980s.

Base/clear paints offer even more protection. The color coat is completely buried under a protective clear coat. The clear coat provides the gloss in the paint.

Modern catalyzed urethane primers and paints offer a finish that can easily last the life of the car. I have found bare metal painted with epoxy primer and top coated with urethane paint offered very effective protection against corrosion.

So, what is an old car person to do?

Nitrocellulose Lacquer is almost impossible to find today. It also cracks easily, and will return to a liquid when exposed to solvents. Lacquer requires sanding and buffing to get a good gloss. Enamel paints are harder to paint, do not have stable color pigments, and oxidize quickly.

An authentic restoration would require the use of the original type of paint. Modern urethane paints do not have the same gloss and color hue; however, they are much more stable. Enamel paints are still available, although somewhat hard to get. Given the time and expense involved in a proper paint job, you have to consider the service life of the paint. Do you want to paint it again in 10 or 15 years?

Modern urethane paints are very forgiving to paint, and last a long time. Modern urethane finishes have a fantastic shine, and require minimal maintenance.

If you want to exactly duplicate an original car, you may want to consider a period correct paint. If you want the best shine, great corrosion protection and minimal maintenance you probably want a modern catalyzed urethane paint. I guess it is ultimately up to the user to decide which way to go.

Just to complicate things, there are new paints being used now which are replacing urethane paints. Waterborne paints are now on the market. Waterborne paints do not have the Volatile Organic Compound exposure of urethane paints. Use of waterborne paint, is being mandated slowly, due to environmental concerns.

Your Car Engine on an Oscilloscope

Guest mechanic this month started with an article from Ken Barber and finished by Wheel Tracks

0818 engine oscilloscopeWhen an oscilloscope is used by a mechanic to tune your engine, the picture to the left is what one good cylinder looks like during one firing cycle.

An oscilloscope allows you to see the voltage pattern of anything that uses voltage. They were first developed in 1932 and can be great for tuning your old car, even if your car is a 1901 vehicle.

The pattern to the left tells you how well your equipment is working, that produces the spark that explodes the fuel in your cylinders, that gives you car the power to drive down the road.

A…. Indicates the level of voltage the coil produces to make the spark at your plug. That little flat part just below and to the left of ’A’ is the moment your points close.

B…. Is called the “Spark Line” where if working properly as in this picture, should decrease in a smooth action to zero. The little wiggles to the right of ’B’ is the final remnants of the spark being absorbed by your condenser. When this does not happen, people radios and tvs get lots of interference, plus your engine can not be properly ready to begin its next firing cycle.

D… This show when the points close to allow voltage back to your coil and be ready to make the next 25,000 volt spark. That little oscillation between D and C is normal and show the voltage settling down while your coil initially starts it’s recharge.

The distance between D and E is called Dwell and is simply the time adjustment for your points to be closed allowing voltage to your coil.

The distance between A and E is simply a time period that one cylinder needs during one cycle. During that one cycle, four things happen.

  1. The gas and air mixture explodes from the spark at the plug.
  2. The exhaust is pushed out the exhaust pipe.
  3. The next mixture of gas and air is pulled into the cylinder.
  4. Then it is all compressed to be ready for the next big spark.

8 cylinder engine oscilloscopeThe picture on the left shows an 8 cylinder engine, all cylinders doing what they are supposed to be doing with the spark plugs firing with 14,000 volts. If a mechanic sees the 3rd vertical lines at, say, 5,000 volts, then he might pull the spark plug from #3 cylinder to see if it is defective.

If the little condenser oscillation is not there like we can see between B and D above, the mechanic can suspect a bad condenser.

On the right is a normal set-up for connecting a scope to your engine.

Scopes are inexpensive these days and you should not let yourself get duped into thinking this is complicated… it is not. The more you use it and the more you see the patterns, the easier it is to find problems and make your engine run as smooth as possible.

A scope can even be used in one-lungers, so hit Napas and ask some questions.

connecting oscilloscope to engine

 

Z Car Update

1972 datsun 240z wheel arch restorationAbsent any questions this month, I will give a brief Z car update. The car is a 1972 Datsun 240Z receiving a total restoration. The car had significant rust in the lower body panels and floor. The left side was much worse than the right side.

Work on the left quarter panel is progressing. The rusty inner wheel well was totally replaced. This involved drilling out the spot welds and removing the old panel. Fortunately, well made replacements are available. The new part was an exact fit. With the new inner wheel well in place, the repair of the outer quarter panel could proceed.

1972 datsun 240z wheel arch restorationWe obtained a Tabco rust repair panel. This panel is made of nice thick steel, but the fit is poor. I like to keep as much of the original car as possible. We went just above the rust, cutting the metal out, just above the rust area. We only cut out the rusty part of the quarter panel, and will weld in the replacement panel.

When fitting a weld repair, I do not like straight lines or sharp angles. I find it easier and stronger to have the weld seam a series of curved lines.

The repair panel was carefully trimmed to fit, and will be welded shortly. It will be spot welded along the wheel well, as original. I may also use two part panel epoxy, this will produce a much stronger, more weather tight bond than it had at the factory.

1972 datsun 240z

Editor’s notes….David and son, Sean, will have the Datsun 240Z at the Shelburne Show on Father’s Day weekend. A beauty of a car, as witnessed in the file picture to the left, is outstanding. Hiratsuka, Kanagawa in Japan is where they were built from 1970 to 1973. The 240Z was meant to compete head to head with the MGB-GT and won the race with its great de-sign and relatively low price.

Time is Money

My Chrysler minivan got a little rusty over the winter. This vehicle is too old to be worth much, but still practical and useful. It is a great vehicle to make the weekly dump run, go to Home Depot and to run errands with. It is also fantastic in the snow with the all-wheel drive system. With these duties, and with two teenage boys in the house it makes sense to keep it, and I can’t justify replacing it.

The lift gate is really too rusty to feasibly repair. A new lift gate is unjustifiably expensive. At the salvage yard I was told a decent used lift gate would be $275, and unless I got lucky and found a silver one, I would still have to paint it.

I found a van with a totally rust free lift gate, but it had a large dent in it. I asked how much they wanted for this one and was given a price of $50.

I had to buy paint to fix the rocker panels, one quarter panel and the front fender anyway. With a couple hours of work, the dent was removed and the lift gate is ready for paint. A couple hours of work saved me over $200.

Above,

Sounds Good – A Bright Idea

led headlightsOne of the headlights recently burned out on one of my Saabs. No big deal, this happens every so often. A set of premium brighter bulbs costs almost fifty bucks, and I have noticed they do not last as long as the regular bulbs. A pair of LED bulbs is only fifteen dollars more, and these will outlast the car. I decided to order the LED bulbs and try them. They are a direct fit replacement for the standard halogen bulb. Unlike many LED bulbs on the market, these bulbs are an engineered replacement for the incandescent bulbs.

On some vehicles, like my Chrysler minivan, the headlight needs to be removed to replace the bulb. This requires removing five bolts and takes time.

In addition to lasting much longer, the LED bulbs do not generate heat, takes far less energy, and you can actually touch the bulb without destroying the bulb. Interestingly, I noticed both old headlight bulb pigtails were partially melted when I installed the LED bulbs.

I will drive with these bulbs for a few weeks to make sure they work, at least, as well as the incandescent bulbs.

I bought these bulbs from superbrightleds.com. I am very impressed with their quality, selection service and price. They list replacement LED bulbs for virtually every bulb in the car.

Sounds Good

sounds goodI recently lost the radio in my every day Saab. I went to crutchfield.com to look at a replacement stereo. I wanted something inexpensive that would simply replace the radio in my car. I was surprised to see the many options and reasonable prices.

For less than 200 dollars, I can fit a replacement radio, with a CD/DVD player, Bluetooth, a video screen and a touchscreen. For a couple bucks more I can add a back up camera.

A unit with all of these features and GPS is roughly the same cost as a stand alone portable GPS unit. Of course, buying the unit from a place like Crutchfield includes plug and play wiring and all hardware needed to make the installation look factory original.

I am amazed at how many features these aftermarket stereos have, and at how much the cost has come down. Now, if I can figure out how to add side curtain air bags, collision avoidance and adaptive cruise control I would never need to buy a new car again.

EASY OIL SEAL INSTALLATION TOOL

easy oil installation toolAnyone who has replaced oil seals without removing the shaft that seals against the seal knows what a struggle the seal installation is. Think of replacing the front main crankshaft seal in place without removing the timing cover or the crank shaft. This job requires applying equal pressure around the circumference of the seal, or it will warp or bend.I have taken several pieces of scrap PVC Schedule 40 drain pipe and cut it in lengths of three inches or so. Interestingly, the diameter of many grease seals is the same diameter of PVC drain pipe. The thickness of the PVC pipe is the perfect thickness to use as an oil seal installation tool.

I have diameters of inch, inch and a half, two inches, two and a half inches, three inch, etc., sitting on my tool shelf, standing in the ready to use for seal installation.By placing the appropriate diameter pipe over the seal the seal can be easily tapped in to place with a mallet. For larger diameter seals, and pipe installation tools, I have a piece of 2 by 4 to place over the pipe before tapping with a hammer.

I Just Can’t Stop!

Let’s face it. Old cars have lousy brakes. Model T Fords only have brakes on the rear wheels, and even those do not work very well. To be fair, the Model T seldom goes over 30 miles an hour.

In the 1950’s and through the 1960’s, cars got bigger and much more powerful. As cars were getting heavier and faster, most still had single circuit drum brakes, many without power assist. Safety standards allowed single circuit brakes through the 1967 model year in the United States. If any brake line or hose ruptured, you had no brakes. If you have an older car with questionable brakes, and you enjoy driving it, you may want to consider upgrading the brakes.

lousy brakesThere are many aftermarket suppliers offering kits to upgrade brakes. Often, the parts were manufactured for later models of similar vehicles, and the parts easily bolt on earlier vehicles.

I believe if you actually drive and enjoy your car, simply upgrading to a dual circuit brake system is an important upgrade. This usually requires simply changing the master cylinder and adding a hard line or two. You may have to also add a proportioning valve. Often, this modification can also include adding power brakes by adding a vacuum booster servo.

Adding front disk brakes is another upgrade to consider. This can also be done after upgrading the master cylinder to a duel circuit system. Adding front disk brakes may involve changing the spindles. There are many kits available with all of the hardware needed for an out of the box bolt on installation.

I recently purchased a new, duel circuit master cylinder kit for the 1959 Corvette. This car is fun to drive, but just can’t stop. This kit is designed to also work with a front disk conversion kit, if I ever decide to go that route.

If you are considering improving the brakes on your car, check parts suppliers catalogues and on line forums to see what is available for improving your brakes.

Engine Management Upgrade

1987 saab 900The distributer in my 1987 Saab 900 Turbo recently broke. Even though it is a Bosch distributer, it is no longer manufactured and parts are not available. This distributer was only used on model years 1986 and 1987. I was able to find a used one; however, several people suggested I upgrade the engine to the later fuel in-jection and ignition system.

The fuel injection and engine management electronics on this car were state of the art, in 1987. Engine management technology improved significantly since.

Saab continued to use this same basic engine right up to the end, and the engine was updated to coil on plug ignition and an improved fuel injection/engine manage-ment system. By upgrading the engine, the engine performance was significantly improved, as was engine efficiency. I have been told to expect an extra 6 miles to the gallon, and an extra 40 horse power with the change to the later components. Another benefit is OBD 2 engine management. Diagnosis and repair of problems is easily handled with a universal OBD 2 code scanner, no more dependence on a Saab Tech II code scanner.

To make the change, I can either take the components off a newer Saab, or buy a conversion kit. The process involves removing the distributer, coil, electronic control module, and the various electrical components and installing the newer components with some extra sensors. Many cars from the 1960’s through the early 1990’s have engines that continued in production through the evolution of modern engine management. Upgrading these engines to modern engine management could be a fun project, with great rewards.