The brass coolant reservoir tank sprang a leak along its edge seal. You can see the hairline crack in the accompanying photo. Since a new unit costs $200+tax+shipping, it was worth trying to repair it. Here’s how it was done.
• Cut a piece of brass shaped to wrap the edges of the tank. The serrations are cut so that the strip can bend smoothly around the tank’s curved corner.
• Clamping it to the top edge on one side, solder it in place, then curve the strip around the corner and solder it to the top edge on the other side.
• Flow solder along the entire top edge, making sure the joint is completely covered.
• Tapping with a small brad hammer, gently bend the brass strip around the tank’s edge. Use pliers to finish bending the strip so that it makes a tight fit against the edge’s underside.
• Flow solder along the bottom seam between the strip and tank edge, ensuring complete coverage.
The first photo shows the tank partially repaired on the left side.
I found that using a 40 watt soldering iron doesn’t provide sufficient heat. A propane plumbing torch provides too much heat, causing solder to slide off the connections. What worked best for me was a butane mini soldering torch (e.g., Bernzomatic #ST250, available at Lowes for $20).
Here’s a shot of the successfully repaired tank.