If the modification is simply replacement of worn out parts (broken ducts, etc), it would probably be repairs. If the expenditure is significant, such as replacing the central unit, or if the expenditure is an addition, such as a computerized control system, then it would probably be a Leasehol Improvement.
It is worn out or the tensioner is weak and needs replacing.
If you hear the squealing when applying the brakes, the pads are worn out and need replacing ASAP. Failure to replace the pads immediately will result in worn out rotors which will also need replacing. If the squealing noise is not when braking it may be a worn drive belt.
Repair it or line it with a plastic bathtub liner.
Worn bearing and new belt is tighter than worn one?
If engine is losing compression it is likely the rings are worn and need replacing. The valves are likely leaking too and need replacing.
A loose timing chain can only be repaired by replacing the timing chain . A loose timing belt means the belt is worn out or the tensioner is worn out. Replace worn parts.
Normally this is caused by a drive belt that is loose or worn and needs replacing.
The belt is loose and needs adjusting, or it is worn out and needs replacing.
You can determine the approximate age of your roof by checking your home improvement records, asking the previous homeowner, or hiring a professional inspector. Signs such as worn shingles, curling edges, or leaks can also indicate the age of your roof.
If you're having to put air in your tires frequently then your tires probably need replacing. Also if the tread on the tires is worn down they should be replaced (a symptom of worn tread is the tires squealing on the road for no apparent reason).
More than likely the shocks are worn out and need replacing.