I did perform a pressure test on my 1999 Buick Century (3.1) and in doing so noticed coolant leaking somewhere from the backside (facing the firewall) of the engine. With no access to a lift, it was somewhat difficult to actually see where the leak is coming from. Where could this be coming from? Thanks!!

Coolant leaks,When the intake manifold gasket cracks or blows out, coolant will leak out of the intake manifold. You may see puddles underneath your car or notice smoke or steam coming off of the engine and exhaust from the coolant dripping onto it and then burning.Overheating, If the intake manifold gasket fails and allows coolant to leak out into the engine, your car will begin to overheat. If your car frequently runs low on coolant or begins to overheat, check the intake manifold gasket.Running poorly, When the intake manifold gasket falters, it affects the way the motor handles its emission gases. The change in pressure can affect the vacuum in the intake as well as how smoothly your car runs. Mainly, it will idle roughly and may hesitate, cough or sputter.

Check condition and operation of thermostat.
Check operation of radiator cooling fan when hot.
Check radiator coolant level. If low, then perform a cooling system pressure check to identify cause of leak.
Check coolant condition. If using water only, then corrosion may build up within system and cause blockages. If blocked, then flush system and refill with anti freeze-water mixture of 50/50.

if you have no visible leaks and it is overheating then it sounds like you have a head gasket leak internally.the coolant is going some where .get the cooling system pressure tested to make sure you don`t have a leak externally.if the coolant is not leaking out the radiator then this indicates the thermostat is not stuck.what ever the problem is change the thermostat at the time of repair.

it sounds like one of several problems radiator needs flushed , water pump is bad or going, thermostat is bad, pin hole in one of the hoses, cracked head, hole in radiator, hole in heater core.if core is leaking you will notice water on the floor inside the car on pasenger side. if radiator has hole when you fill radiator with coolant it will leak froom fins sometimes only when hot. thermostat bad your car will read hot and or cold always. if stuck open cold, if stuck closed hot, after about 15 20 mins of running engine will cause radiator to boil over to over flow tank.never open radiator cap when engine is hot :) burn hazard.if pump is bad or going will notice gauge reads hot intermittent or always. will boil in to overflow tank. if head is cracked will notice water comming from side of engine block or in oil when you change oil. if radiator needs to be flushed will notice scale or gunk on radiator cap
(if you think you need help or do not have tools to perform please take to a machanic)

freeze plugs are normally on the sides of the engines, check to see if hose connected to thermostat housing is not leaking, and also check to see if coolant is coming from the water pump.

Have someone pressure test the cooling system - you likely have a head gasket leak

would need more info mileage,check engine light status on,off,blinking? how often does this happen once a day,week,etc? with what your info that you have given. no coolant leaking in oil will not cause intermittent gas no or little car movement.lower intake gaskets are prone to leakage guessing you buick is a 3.1 or 3.4.may be catalyic converter blockage if material is brocken up inside and moves around and blockes exhaust. may here rattle under acr or happens more when car is hot or longer rides. hope this helps. you are more than welcome to provide more info if you need more help.

The thermostat must be failing. Consider replacing it.

A pressure test will pin point the leak. But make sure it isn't the lower intake gasket. Pretty common area for coolent leaks on these cars.

One good way to find where a coolant leek is coming from - is - when you get home and the car is good and warmed up - "hot".. Park it up on ramps if you have them.. Right after you shut it off - it will build even more pressure in the cooling system.. At this time car is off - open the hood and look (from under the hood and from under the car if you have ramps) for leeks,, listen for the "hissssss".. If the leek is just to small and/or to difficult to find - take it to a shop or oil change place for a compression test of the cooling system to locate the leek..

Hopefully its just a hose leek..


Good luck..