I have a 1990 gmc 1500 5 speed that is overheating and leaking coolant i changed the radiator hoses,thermostat, and water pump, and i know the leak is not coming from the radiator what do i do next?

A worn water pump is the most likely. If the coolant is going down, the water is going somewhere.

The most common reasons an Oldsmobile Alero is overheating are a coolant leak (water pump, radiator, hose etc.), the radiator fan, or a failed thermostat. Coolant leak (water pump, radiator, hose etc.)

Oldsmobile Alero Overheating - RepairPal

Videos on overheating. You probably have air in the system from when you replaced the thermostat. The coolant system needs 'burping' of air.

https://www.google.com/search?q=2000+Oldsmobile+Alero+running+ho

Burping

https://www.google.com/search?q=burping+coolant+system

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An overheated engine can be caused by anything that decreases the cooling system's ability to absorb, transport and dissipate heat; therefore engines can overheat for a variety of reasons. Let's take a look at some of the most common causes.
Cooling System Leaks
This is the primary cause of engine overheating. Possible leak points include hoses, the radiator, water pump, thermostat housing, heater core, head gasket, freeze plugs, automatic transmission oil cooler, cylinder heads and block. Perform a pressure test. A leak-free system should hold pressure for at least one minute.
Wrong Coolant Concentration
Be sure to use the coolant recommended by your vehicle's manufacturer. The wrong type of coolant and/or mixing the incorrect concentration of coolant and distilled water can also result in engine overheating. The best bet is to perform a complete flush and fill.
Bad Thermostat
A thermostat is a heat-sensitive valve that opens and closes in response to engine temperature. Heated engine coolant passes through to the radiator when the thermostat is in the open position. In the closed position, it prevents the flow of coolant to speed up the warming of a cold engine. When the thermostat gets stuck in the closed position, coolant stays in the engine and quickly becomes overheated, resulting in engine overheating.
Blocked Coolant Passageways
Rust, dirt and sediment can all block or greatly impede the flow of coolant through the cooling system. This can limit the system's ability to control engine temperature, which may result in higher operating temperatures and engine overheating. Once again, a flush and fill is recommended to remove debris.
Faulty Radiator
By passing through a series of tubes and fins, coolant temperature is reduced in the radiator. Leaks and clogging are some of the most common causes of radiator failure. Any disruption in the radiator's function can lead to elevated engine temperature and overheating.
Worn/Burst Hoses
A hose that contains visual cracks or holes, or has burst will result in leaks and disrupt the flow of engine coolant. This can result in overheating.
Bad Radiator Fan
A fan blows air across the radiator fins to assist in reducing the temperature of the coolant. A fan that wobbles, spins freely when the engine is off, or has broken shrouds will not be able to reduce the temperature to proper level, thus possibly resulting in engine overheating.
Loose or Broken Belt
A belt is often the driving link that turns the water pump at the correct speed for proper coolant flow through the cooling system. If a belt is loose or broken, it cannot maintain the proper speed, thus resulting in poor coolant flow and ultimately, engine overheating.
Faulty Water Pump
Known as the 'heart' of the cooling system, the water pump is responsible for pressurizing and propelling engine coolant through the cooling system. Any malfunction of the water pump, including eroded impeller vanes, seepage or wobble in the pump shaft, can prevent adequate coolant flow and result in engine overheating.

The overheating probably came from the coolant being too low. The coolant in the reservoir won't go back into the radiator if the coolant in the radiator is too low. Until you get it fixed, check and fill up the radiator every time you want to use it. Overheating is very bad for engines and can cause expensive engine repairs.
Where is it leaking, from the engine or the radiator? You didn't say, but wherever it is leaking is the place to start. If at the radiator, and it is not a loose or leaking hose, I would be looking for a new radiator. If it is leaking at the front of the engine and dripping down from there, you could have a bad water pump. This could be an expensive repair at a shop-not the pump itself-they are not too expensive-but the labor cost in replacing a water pump will add up.

The thermostat would not cause it to leak. But when all is said and done, you will want a new thermostat, after the leak is fixed. They are very cheap and it is just good insurance.

yes. the impellor on these engines have a tendency to come off the water pump.First you can see if the pump is working by removing a heater hose then have someone to start the engine. if the water sprays a good, solid stream out then the water pump is good. if the water just barely comes out or not at all then the pump is weak or "bad".

Two things would cause this

There is a slow leak and the radiator is low on fluid

Let the vehicle cool down completely and then check the level in the radiator. I bet its pretty low. Top off the radiator with a 50/50 mix of coolant and water. start the vehicle and let it warm up with out the radiator cap on. Keep adding fluid as necessary. While waiting for it to warm up check around for any abvious coolant leaks. Things like hoses, radiator seams, water pump, water inlet/outlet gaskets. If no leaks are found it may be necessary to pressure test the cooling system and even then it might be a slow leak that only occurs when the vehicle is cold.

If the radiator is full than I would suspect that water pump is no longer working or creating enough flow. If the thermostat where stuck you would still get heat. If the water pump is not circulating coolant than you would get no heat and the car would overheat.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

CHANGE THERMOSTAT AND RADIATOR PRESSURE CAP.CHECK COOLANT LEVEL.MAKE SURE YOU HAVE 50/50 ANTIFREEZE AND WATER.MAKE SURE COOLING FANS COMING ON WHEN ENGINE REACHES 190 DEGREES.TO SEE IF COOLANT FANS RUNNING TURN ON CAR AIR CONDITIONER TO SEE IF FANS RUN IF NOT CHECK COOLING FANS FUSES.IF FUSES GOOD I AM LOOKING AT A FAULTY COOLANT TEMPERATURE SENSOR.IF ALL IS GOOD.NO LEAKS AT RADIATOR HOSES + HEATERS HOSES. NO LEAKS AT WATER PUMP WEEP HOLE OR GASKET.NO LEAKS AT RADIATOR.LAST RESORT CHECK ENGINE OIL. IF LOOKS LIKE MILK SHAKE YOU HAVE LEAKING HEAD GASKET.THAT WILL CAUSE ENGINE OVERHEATING.

check and make sure the bolt holding your water pump are on good and check the hoses

check coolant level,if its not full check for leaks,hoses,water pump,rad and heater core.if level is ok,thermostat is located in housing where top rad hose connects to motor.

Check the radiator and hoses for leaks. Also, look at the water pump and see if any coolant is leaking out of the vent or "weep" hole. If coolant is leaking from the weep hole, the water pump is defective and will need replaced. When checking hoses, look for cracks and leaks, especially around the hose clamps. Hope this helped and best wishes.

Hello Ranger Joe, eight months and two radiators is very uncommon. Question, Have you visually confirmed the leak in the radiators or is the leak near the hose connections? Replacing the radiator, cap, water pump, & the thermostat leaves only two others, the hoses and the engine block/heads. Far fitched will be something or somebody poking holes in the radiator.