No need to pull the timing chain. Remove drive belt and then remove the crankshaft pulley. use a screwdriver with a piece of cloth wrapped around the tip so you don't damage the seal bore. place the new seal square with the bore and use block of wood or a socket smaller diameter than the seal and a rubber mallet to insert the seal flush with the crankshaft bore. put back on the pulley and tighten according to torque specs in your shop manual then reinstall the drive belt and run engine to check for leaks.
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you have a vacumn leak.
cracked hoses
water leak or bad thermostat
We are going to need to know where the source of the leak is to help you with that question.
The simple and really only answer I can give you is to find the leak and repair it.
your front windshiald has a leak
Because there is a hole in the hose! Replace the hose
replace fuel cap with Nissan only OEM replacement.
replace the hose or gasket the is leaking, you can spray carb cleaner around the eng whil runnig to locate the leak the eng will try to stall
the valve cover gasket is bad, or the valve cover is loose
It will more than likely leak not make a funny noise. They have a releif for pressure when they go bad.
you may have a loose seal or a pinhole leak i would get it checked out asap