Q. There is a crack in my foundation wall that goes from under a window down to the basement floor. On the outside there is a sidewalk next to this wall. Water comes in whenever it rains. Some say that fixing from the inside would be useless -- that I must dig up that part of the sidewalk and dirt on the outside so the wall can be repaired from the outside. What do you think?

A. I'm afraid this advice is correct. Unless you make repairs from the outside, the likihood is that the repair will not last or that the water will find its way in at another point.

Q. My house is heated with hot water, and the boiler has two valves in the cold-water line leading to it. One is an automatic feed that supplies water when needed, and I believe the other is a safety that is supposed to release water when the system is overfilled. During the past year about half a pail of water comes out of this safety valve every day while the furnace is running. I have lived here for 10 years, but never had this problem before. Do you have any suggestions?

A. The expansion tank is probably full of water; it should be full of air, or at least two-thirds full of air. This tank is usually located directly above the boiler and has a drai valve on the bottom. Turn off the boiler and let the system cool, then open the drain valve on the expansion tank and drain all the water out. If yours is an older unit, the expansion tank may also have another valve on the inlet water line leading to the expansion tank. If so, shut off the inlet valve before opening the drain valve at the bottom. After the tank is drained, close the drain valve, open the inlet valve again (if you have one), then start up the system in the usual manner.

Q. When a serviceman came in to work on the air-conditioning compressor in my backyard he managed to drip some oil on the brick patio and steps, as well as on the concrete walk leading to them. Do you know how I can remove these stains?

A. Use a liquid driveway cleaner (sold in most hardware stores) to clean the grease off the bricks. Brick is much more porous than concrete, so the oil will have penetrated deeply, and you may not be able to get it all out, but you should be able to remove much of it. You can then camouflage the stains (if they are not too large) by rubbing over them with a scrap piece of the same kind of brick.

Another method that often works is to cover the stains with dry powdered portland cement, then saturate this with paint thinner to form a paste. Cover this mixture with plastic to keep it from drying out and leave it in place for an hour or two. Then remove the plastic and sweep or vaccum the cement-paste mixture. Do not try to wash it off with water: This will cause it to soak in and further stain the brick.

Q. Is there any product you can recommend that will clean the stained marble top on an old dresser?

A. Marble stains are taken out with a poultrice made by mixing a solvent with chalk powder to form a paste. But you have to know what caused the stains, because different solvents are used for different stains.