The reservoir was dented from below and now leaks. I removed and patched with fiberglass and resin (like a surfboard), but that didn't last. Anyone recommend a product to seal a crack? I think a new one costs $41.
Thanks.

If sticky stuff doesn't work, try a mechanical solution.

Attach a patch - backed with soft rubber - with a bunch of sheet metal screws.

You could go to the net, or a salvage yard. Perhaps the bottle from another model?
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96 855R, 95 855,854, 90 744 Ti - 340,000 Volvo miles put on 7 bricks

For that low cost, and to repair the problem properly, I would replace the unit.

The reervoir is made of polythene. Cut strips from a polythene container (ie. windscreen washer fluid container, fruit juice container), cut 1/4 inch strips, light it with a lighter and let the molten polythene drip onto the crack. Trim with sharp knife and sand with sanding block.

I like it. It's cheap and it involves cutting and burning.