A Positively Good Idea

Recently I attended a SCCV driving event. Part of their pre-event inspection is verification of a cover for the hot battery terminal. I checked my car a few days before, and realized the positive battery terminal was not covered. I spent a minute thinking of all the possible ways the positive terminal could be accidentally shorted to ground. If nothing else, when working on the car, a wrench or other tool could easily be accidentally dropped, causing a direct short. 

The positive terminal is just a few inches from the aluminum A/C lines, the inner fender, and numerous bare nuts and bolts. I can understand the concern, the battery could easily be accidentally shorted out. 

I went to the local auto parts store and bought a pair of universal battery terminal covers. I had to cut it a little to make it fit my car. Just for good measure, I used a red zip tie to hold it in place. 

I passed the safety check with no issues, they checked to ensure the battery was securely held down, that the hot terminal is covered, the front end was tight, and there was nothing loose on the body of the car. 

I have also decided that the hot terminal of all my cars will be covered, as an extra safety measure. The $5 spent for terminal covers is cheap insurance and piece of mind. These covers can easily and quickly be removed for display on show cars. 

My rear disc brakes with the emergency drum brake

disc brakes with emergency brake
An example of a drum emergency brake with regular disc brakes. 

This was the good news! Something strange happened to me last week. I loaded the garbage and the recycling into the minivan to do the Saturday trip to the transfer station, and the right rear wheel locked up when I backed up. As this happened, the rear axle made unpleasant noises. I thought the parking brake was seized, and was relieved when the wheel moved ok going forward. 

On the way home, the right rear wheel locked up while driving forward, making horrific noises. Again, I thought the noise was originating from the rear axle. I definitely heard the differential banging against the frame cross member it is mounted on. I drove up my driveway, with the wheel seized. I googled the problem, and found many stories of the rear differential failing, causing a rear wheel to lock up. Fortunately, the part is available rebuilt, but they are expensive. 

I planned on removing the differential to verify it was in fact bad before I purchased a used or rebuilt unit. I thought I should check the right rear hub first to rule out any problem there. Fortunately, I found the problem. This vehicle has four wheel disc brakes, with the parking brake on the rear. The parking brake has conventional brake shoes on a drum in the center of a “hat” type rotor. Somehow, something came apart with the parking brake assembly, and the whole assembly broke apart and jammed against the rotor. I have to replace the backing plate, caliper mount, rotor and the whole parking brake assembly. It is bad, but infinitely better than a bad differential. I have never seen anything like this before. 


A few more points about BEARINGS 

Pictured below, and the following is an article from the December, 1960, “Science and Mechanics” magazine. 

Bearing Lubricates Itself 

wheel bearings

Designed to replace ball bearings and have several times their life expectancy, this new Hy-Film bearing never requires relubrication. It utilizes the phenomenon of hydrodynamic oil film. The diagram at left: (1) Oil is drawn from reservoir through bearing window; (2) rota-tion of inner tace under load generates hydrodynamic oil film, supporting race without metal contact; (3) oil forced to bearing ends by film pressure lubricates thrust washer and (4) oil is picked up by slinger and returned to retaining cup, where it is reabsorbed by Permawick in oil return hole. Tann Bearing Company of Detroit, Michigan, designed and developed the bearing. 

What is hydrostatic and hydrodynamic bearing? Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and the pressurization is done by a pump. Hydrodynamic bearings rely on the high speed of the journal (the part of the shaft resting on the fluid) to pressurize the fluid in a wedge between the faces. 

What are the types of bearings? There are many types of bearings, each used for different purposes. These include ball bearings, roller bearings, ball thrust bearings, roller thrust bearings and tapered roller thrust bearings. 


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I am running out of ideas on what to write about in this column. If you have any ideas, or any questions you want me to answer, please let me know. 

Dave’s Garage…email: dasander@aol.com 

One Thing Leads to…

With no questions to answer this month, I thought I would share an interesting story. 

Have you ever been putting off a big job, expecting it to be difficult, only to be pleasantly surprised at how simple it is? I have had this happen to me. I have also had what should be very simple job turn out to be a nightmare. I recently had what should have been a simple job turn out to be a much bigger job. 

In August I lost the clutch in one of my Saab 900s. This car was from Southern California. It has never seen salt, and rarely saw rain. It is a fun car to work on. Nothing is rusted or frozen. 

saab 900s clutch

Now, on a Saab 900 the engine is bolted on top of the transmission, and the whole assembly is mounted backwards in the car. The clutch is on the back of the engine, which is up front by the radiator. I have done a complete clutch job in about an hour. It is a relatively quick and simple job. 

I realized the problem with the Saab clutch was the master cylinder. I ordered a new one and attempted to install it. It is a traditional master cylinder attached to the firewall with two studs. I was just finishing the installation when one of the studs broke off. I was just tightening the nuts on the studs when the wrench came loose. I had just begun to snug the nut, I hadn’t even begun to apply much tightening force. I removed the part to find that the ear, the stud was threaded into, actually broke off. It was a defective casting. Ok. No big deal. I obtained a replacement and installed it. 

When I drove the car to work the next day I noticed the cruise control no longer worked. Somehow while working under the dash I broke the cruise control. On the way hone, I lost the clutch again. A quick inspection revealed the hydraulic hose between the master and the slave burst. Ok, not a big deal. I replaced the hose. As I was bleeding the clutch, the slave cylinder blew. To replace the slave cylinder the entire clutch assembly needs to be removed. When I removed the clutch assembly, I noticed the rear main seal on the engine, and the pilot shaft seal on the transmission were leaking, the clutch had oil on it, and the pilot bearing was seized. I ordered a complete clutch kit, and new seals. I resurfaced the flywheel while it was apart, and installed the new seals and the new pilot bushing. 

I had a bear of a time installing the new clutch, it just did not fit. I couldn’t align the pressure plate quite right to install the bolts, and the pilot shaft just would not fit in the clutch disk. After wrestling with it for over two hours, and cutting my hands several times, I realized I had the wrong parts. They were boxed wrong. I had ordered the right parts, but the parts supplier gave me the wrong parts. After a conversation with the parts supplier I received the correct parts, and again attempted to install the clutch. I had it almost installed, when I realized one of the dowel pins fell out of the flywheel. I had to take the assembly apart to get the pin out of the bell housing. After reassembly I was installing the slave cylinder bolts when one of them stripped. I could not understand how it stripped, as I never snugged the bolt. Again, the whole assembly had to come apart to fix the stripped threads. I realized someone had installed the wrong bolts at some point, these bolts were too short, and one was cross threaded. 

The project is almost done. Hopefully I just have to bleed the clutch and finish putting it back together. Should be done this weekend, almost four months later… 

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.

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.

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.

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.

It’s in the Bag

When doing engine work or restoration work, organization is key to success. I recently overhauled an engine in my shop, and I was greatly aided by a careful and thoughtful organization when I took the engine apart.

I carefully catalogued the nuts, bolts, hardware and parts in zip lock bags, carefully labeled with a sharpie marker. The valve cover bolts were placed in a sandwich sized bag, labeled valve cover bolts, Left. The head bolts and miscellaneous hardware were placed in quart sized bags and labeled. These bags were then placed, in a gallon sized bag, labeled and Left.

This method continued through the engine disassembly. The oil pump bolts were bagged, and placed in the bag with the oil pump. All of the bags of parts were placed in a box with all the other parts.

When I reassembled the engine, all of the nuts, bolts and miscellaneous hardware were easily located, and the order of opening and unbagging the parts, easily gave me what I needed without wasting time searching, and minimizing the risk of placing the wrong hardware in the wrong location. When installing the left cylinder head, I grabbed the bag labeled Left, and all of the hardware was clearly labeled. When I was done, all the hardware was accounted for. There was nothing missing, and nothing left over.

I also use this strategy when I take a car apart for major work or restoration. There is nothing more maddening than not being able to find a part when needed.

Zip Lock freezer bags have an extra strong zipper, and provide a white rectangle for labeling. The next time you are in the grocery store, I would suggest buying a few boxes of sandwich, quart and gallon sized zip lock freezer bags for your shop.