Pontiac Repair: 1995 pontiac grand am leaking coolant, coolant temp, radiator hose

Question
 I have a 1995 pontiac grand am with 121,000 miles.  It has a 3.1 engine and has just had a fuel pump replaced.  

  The problem is for the last month coolant has been leaking from the radiator through the cap.  I haven't had it formally inspected but no other leaks can be found.  It will only do it every 2 days or so.  I had the thermostat replaced and it still kept doing it.  The cap is practically new so that can't be it.

Now I'm hearing a thumping noise when I turn the car on and when I park but only for a few minutes.  It comes and goes.

I was told the engine was about to go out.

Please Help

Answer
i would check the coolant temp when this happens.if the engine is overheating it can cause boilover.the coolant will blow out the radiator when this happens.also make sure that there is adequate coolant flow.squeeze the top radiator hose when the engine is hot and feel for pressure build.if there is no pressure than the water pump needs replaced.also make sure that youre cooling fans are kicking on when they are suppose to.if these fail the engine will overheat.make sure that the radiator cap is the correct one for youre vehicle.these are rated by pressure and yours should be at least 15 pounds.and last but not least and im not saying this is whats wrong but it could be a head gasket or cracked head.this would be my last option as it is the most expensive.all of these are repairable and finding a reputable mechanic that wont rob you is your best bet.you can of course save some cash by purchasing a quality repair manual and doing the repairs yourself.good luck