Mon Sep 24, 2007 4:55 pm
Shade Tree Rehab: Water Outlet Elbow
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As I was working on the '51 front end, a little mission creep started to happen. The next thing I know, the radiator casting was removed from the engine which left the water inlet and outlet pipes exposed. So off they came to be cleaned up and painted. And all I wanted to do was paint the front wheels and mount new tires... Anyway, I pulled the water oulet elbow off the head, sand blasted the casting inside and out and noticed lots of pits in the neck. Here is a picture of the water outlet elbow when it was removed from the tractor:
As I looked at the corrosion, it became clear that band clamps on the rubber hose were not going to be enough to stop coolant leakage on top of the engine. I know the Cub is water cooled, but I doubt that IH meant for the coolant to dribble onto the head. This is how I rehabilitated the water outlet elbow. The same techniques could be applied to other fittings as well.
- Getting To Competent Metal
The first step was to get to competent metal around the neck area. The pits I saw could have been caused by rust or they might have started as molding sand cavities which became rusted. After wire brushing the neck area, the metal looked smooth but these funny looking black spots did not seem to get shiny like I would have expected from brushing. Using a pocket knife, I dug around in a few of the pits and non-metallic flakes fell out. They were almost like the flux glaze left over after brazing. Once I dug out all these inclusions, I wire brushed the surface.
- Crater Filling Materials
Once I had good metal, the decision was how to fill the craters or pits left by the corrosion and sand inclusions. There are several options depending on the depth and severity of the damage. For very severe craters or holes, I fill as much as possible with brass brazing rod. This solution fills the spaces with metal which has expansion and contraction closer to the parent metal than other filler materials. If the damage is less severe, I use JB Weld and/or a 2-part body putty. Either of these will work and what you use will depend on what feels most comfortable for you.
- Filling the Craters
To fill the craters with brazing rod, heat the piece with an oxygen/acetylene torch, dip the flux coated rod into the fire and fill the pits. To use one of the plastic fillers, like JB Weld or body putty, you need a fence to keep the material in place while it cures. I use a strip of paper, a little wider than the area to be built up. The technique works like this.
When the filler material has cured, remove the tape holding the fence in place. You can now, either carefully peel away the fence material or put the elbow into a bucket of water. The water will soften the fence material and a little bit of work with a ScotchBrite pad will remove whatever is left behind.
- Clean the metal surface throughly with Acetone or Alcohol
- Mix enough filler to completely cover the entire surface to be repaired. If the pits are in just one area, cover the whole thing anyway.
- Apply the filler to the surface with a piece of plastic, old credit card, putty knife, or whatever has a straight edge.
- Take the fence material, paper or manila folder or... and tightly wrap it around the filler material.
- Use a piece of tape to secure the end of the fence to itself. This is a good use for cheap electrical tape. It is stretchy and will stick long enough for the filler to cure.
- Check that the fence is tight and round when viewed from the end.
- Let the filler set up. Depending on what you use, it can take 20 minutes to several hours. So walk away and do something else. Avoid the temptation to peek.
You should now see the elbow with a relatively smooth surface that was cratered. To finish the job, take a piece of sandpaper, 100 or 120, and sand the surface with a twisting motion like twisting a motorcycle throttle. If you feel the need for more smoothing, either put another layer of surfacing material on using another fence, or fill the existing surface with Automotive Glazing Putty.
This is what the elbow looked like after the JB Weld was sanded and Glazing Putty was applied and sanded:
- Fence Material Considerations
To work well as a fence material, we need something which is stiff enough keep the filler in place until it cures. But it has to be flexible enough to wrap around the end of the elbow. We also need to be able to remove the fence after it has done its job. A piece of stainless steel shim stock would certainly satisfy the stiff yet flexible requirements, but removing it may be tough. A strip cut from a manila folder is sufficiently stiff and flexible. A good piece of typing paper also fits the description. When the fence is rolled around the mouth of the pipe it needs to form a cylinder so the filler can fill the low spots and be squeezed out of the high spots. Typically the mouth will be somewhat oval in appearance before the filler is applied and should be cylindrical after the fence is removed. When preparing the fence be aware that stiff but flexible materials usually will not conform to the lip where the fence begins. The following illustration shows what will happen and how to avoid the bump.
In the top image, the fence laps over itself creating a void shown in red. This void will contain filler material and unless it is cut down, you will have created a natural path for water to escape. By putting a scarf joint in the fence material, the overlap is non-existent. The easiest way to make a scarf joint is to sand the edge of the fence stock so the overlap lies flat.
- Finishing Up
Here is the elbow painted and ready to go back on the tractor. Notice how round and smooth the mouth is. (And the body color is fabulous!) The white paint on the inside of the elbow is actually Tub and Tile Repair Paint. It is sold to repair chips in porcelain/cast iron tubs and such. It is pretty useless for the intended function since it goes on too thin and the color match is poor. However, it is a two-part epoxy and can be re-coated several times. When this epoxy cures, it retains some flexibility making it ideal as a lining for the inlet and outlet pipes on the Cub. Look for it in old time hardware stores or the clearance sections of Big Box Stores.
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