2003 Volvo S40 Exhaust manifold leak

Labor will be around 5 hours so multiply that by the shops hourly rate. Parts varies but you will need the manifold gasket, turbo return seals, 6 copper washers, turbo gasket, maybe cat to turbo gasket if applicable, and a gallon of coolant. They will also need to check the manifold for warpage and cracks. If it is badly warped or cracked then you will need that also.

Is it a big problem? need to repair immediately or not?

Thanks a lot

Depends on how bad the leak is? If it is minor, you could get a check engine light on with codes for oxygen sensor faulty signal. But if it is pretty bad and you can actaully smell the exhaust fumes, then that can be dangerous since you could be breathing in carbon monoxide which is highly toxic and can actually make you very drowsey if driving long distance! For this 2003 I am going to assume the exhaust nuts have come loose and maybe one or two may have fallen out. At the minimum have the missing nuts installed and the rest retighten. If it stops the exhaust leak noise then you should be O.K. for a while but will only be a temporary fix. If it does not help then the exhaust gasket has blown out already and you will definatley need to replace them and check the manifold for warpage!