1999 Pontiac Grand Am with "lower intake leak"...What does this mean specifically? Would this mean the intake for the radiator, gasket, or valve?

Check for coolant in the the oil the 99 is notorious for the lower intake gasket going out

Can be a cracked radiator, bad hoses leaking at the thermostat or the upper intake or lower intake maybe even a head gasket blown. Your looking at around 400 if u got a leak anywhere other that a radiator or hoses

you have a GM common problem and that is a bad intake manifold gasket. GM change the gaskets to plastic and they crank and leak causing over heating. here is a picture of one i took from a 2005 pon. bonneville with 74,000 miles on it

Have a cylinder leakage test or co2 test done. my prefered method is a leakage test as it checks heads, head gaskets, valves, rings all in one test.

if you have a freeze plug leaking oil you've got major problems....freeze plugs or expansion plugs are for engine coolant only, they are there in case the coolant freezes it will pop out one of those plugs before it cracks open the engine block. at least in theory. you should probably start with the valve cover gaskets and then do upper and lower intake gaskets...

The first things to do are: 1. Make sure the radiator is full when the engine is cool (check the fluid in the radiator as well as the overflow tank). 2. Make sure the thermostat is working. 3. Have the lower intake manifold gasket checked. The Grand Prix SE came with a 3.1L engine (standard) and these engines are famous for lower intake manifold gasket problems.

yes,,and you should as they are very known forn leaking

Are you adding coolant?
Yes ......means it's going somewhere.
Fill the coolant tank to the top...right to the top....leave the cap off and run the engine.
If you see bubbles you need a head gasket.
The intake gasket is another source of coolant leaks and at this area the coolant can be sucked into the engine and produce a white smoke.
Does the car run rough at the first start in the morning....could be antifreeze burning off in the cylinder or area that was leaking overnight meaning cyl gasket or intake gasket.
Look at the rear head to block area below the exhaust manifold.
Is there any trace of coolant or stains of coolant......yes means head gasket time.
Pressurizing each cyl at a time with air with the valves closed in that cyl will quickly show the location of the bad head gasket with bubbles coming out of the fill tank on the bad cyl (s).
Head gasket leaks don't always mean milky oil.

1 Inspect Cooling System Mix Coolant level low or flow is restricted. 2 Inspect Belt Incorrectly routed, adjusted, tensioned, missing, or worn water pump belt(s). 3 Inspect Oil Pan Gasket - Performance Ruptured, cracked or leaking radiator hose. 4 Inspect Radiator Cap Worn or damaged radiator cap 5 Inspect Thermostat Thermostat stuck closed 6 Inspect Fan Blade Broken, missing, or defective fan blade(s). 8 Inspect Water Pump Damaged, worn or leaking water pump. 9 Inspect Intake Manifold Plenum - Perform Leaking water pump gasket. 10 Inspect Cooling Fan Control Faulty cooling fan control or circuit. 11 Inspect Cooling Fan Switch - Radiator Faulty radiator cooling fan switch or circuit. 12 Inspect Engine Temperature Sensor Faulty engine temperature sensor or circuit. 13 Inspect Temperature Switch Damaged or faulty temperature switch or temperature switch circuit. 14 Inspect Fan Clutch Worn, loose or faulty fan clutch. 15 Inspect Ported Vacuum Switch Damaged, leaking, or faulty ported vacuum switch. 16 Inspect Radiator Obstructed radiator core or radiator cooling fins. 17 Inspect Head Gasket - Performance Head gasket leaking coolant into cylinders

Better check to see if the water pump is leaking, or if the radiator hose has a leak or the radiator it self. Also, could be the thermistat sticking. Better get checked if not you'll be replacing the intake gaskets and the head gaskets. If it gets too hot the it could ruin the motor or warp the heads and that is very costly. If the heads get warped it is possible they can be fixed. Hope this helps.