My car is leaking coolant. Also after it runs for awhile the idle gets low and then shuts off. Sometimes it cranks back on but shuts off again until it cools. Whats the problem?

Souds like it's way low on coolant. The heater will blow cold air when the cooling system is so low that there is no water (coolant) running through the heater core. Then the thermostat opens, it trys to be normal but the system is low so it gets too hot in just a few minutes. If its that low, there must be a leak somwhere.

vacuum leak. get some brakekleen and spray the edges of the intake manifold where the manifold meets the heads and when you get a smooth idle thats your leak. also try it on every vacuum line

check ignition pick up its in the distributor. its responsible for spark in the plugs

REPLACE THE THERMOSTAT AND RADIATOR PRESSURE CAP.IF COOLANT LOW, ADD MORE COOLANT THROUGH COOLANT OVERFLOW UNTIL COOLANT LEVEL IN THE COOLANT OVERFLOW STAY AT FULL COLD MARK.REASON POUR COOLANT THROUGH COOLANT OVERFLOW MOST GM CARS DONT HAVE RADIATOR CAP.WHEN YOU GET COOLANT LEVEL OKAY, CRANK CAR LET IT IDLE UNTIL ENGINE GET HOT BUILD UP PRESSURE THEN TURN OFF CAR.CHECK FOR COOLANTS LEAKS AT THE RADIATOR HOSES,CHECK FOR LEAKS AT THE RADIATOR, CHECK FOR LEAKS AT WATER PUMP WEEP HOLE IF YOU SEE COOLANT LEAKING FROM WEEP HOLE REPLACE WATER PUMP. IF CAR OVERHEATING WHILE IDLING YOUR COOLING FANS NOT WORKING CHECK COOLING FANS FUSE AND RELAYS.IF FUSE AND RELAYS OKAY THE ENGINECOOLANT TEMPERATURE SENSOR BAD.

ADD COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND COOLANT LEVEL STAY AT THE FULL COLD MARK.PLACE COOLANT OVERFLOW JUG CAP BACK ON JUG.CRANK VECHICLE UNTIL ENGINE START WARMING UP. STOP ENGINE WAIT FOR A WHILE UNTIL COOLANT COOL DOWN TO KEEP FROM GETTING SCALDED. USE A LARGE RAG OVER THE OVERFLOW JUG CAP OPEN OVERFLOW JUG CAP A LITTLE AT A TIME REMOVE OVERJUG CAP CHECK COOLANT LEVEL ADD MORE. COOLANT IN THE OVERFLOW JUG.THEN START VECHICLE AGAIN.LET ENGINE IDLE UNTIL TOP RADIATOR GET HOT.THEN THERMOSTAT WILL BE OPEN.WHILE ENGINE IDLING WATCH THE TEMPERATURE GAUGE IN VECHICLE IF TEMPERATURE GAUGE START CLIMBING IN THE HOT ZONE.TURN OFF VECHICLE LET IT SET A WHILE THEN USE LARGE RAG REMOVE OVERFLOW JUG CAP.ADD MORE COOLANT, PLACE CAP BACK ON START VECHICLE AGAIN KEEP DOING THIS PROCEDURE UNTIL TEMPERATURE STOP CLIMBING HOT ZONE.AND WHEN COOLANT LEVEL STOP DROPPING IN THE COOLANT OVERFLOW JUG.AIR IS OUT THE SYSTEM, BUT KEEP COOLANT LEVEL IN THE COOLANT OVERFLOW JUG AT THE FULL COLD MARK.DONT OVERFILL.DONT LET COOLANT OVERFLOW JUG RUN DRY IF SO AIR WILL ENTER COOLANT SYSTEM BECAUSE COOLANT LEVEL WILL BE LOW ENGINE WILL START OVERHEATING.

There are several possible problems causing the temp increase.

1. Low coolant level
2. Leak in radiator hose
3. Leak in radiator
4. Bad waterpump

With low coolant levels by any 1 or a combination of 1-4, the vehicle will run hot at low speeds and at idle. Running the AC or heater pushes the remaining coolant through the system faster, aiding in cooling the engine but all indications are you've definitely have a cooling system issue that should be looked at immediately before doing damage. If the coolant level is good (when car is cold, open radiator cap and check for coolant level), the issue most likely lies in the waterpump.

IF LOW COOLANT LIGHT CAME ON ENGINE SHUT OFF BECAUSE IT GOT TOO HOT AND OVER HEATED.WHEN YOU HAVE LOW COOLANT.YOU COULD HAVE LEAKING RADIATOR.YOU COULD HAVE LEAKING RADIATOR HOSES AND WATER PUMP. ADD MORE COOLANT IN CAR RADIATOR UNTIL YOU AT FULL COLD MARK ON THE OVER FLOW COOLANT TANK START THE CAR LET IDLE UNTIL ENGINE GET OPERATING TEMPERATURE.RAISE YOUR HOOD LOOK FOR LEAKS THE RADIATOR PRESSURE WILL PUSH COOLANT OUT WHERE LEAKS COULD BE.LOOK AROUND RADIATOR AND COOLANT HOSES.LOOK AT WATER PUMP.IF YOU SEE COOLANT LEAKING AT WATER PUMP REPLACE IT.

ok you have probably more than one problem first coolant leak im not sure which engine you have in your car but if it is the v six check at the tensioner there is to small ninty degree pipes they have orings on both ends of them and they typically start to leak motormite makes replacements for them if your car is continueslly running hot that can confuse your ecm and cause it to run lean or rich on fuel which will effect its idle small vacumm leaks can cause issues as well you can take throttle plate cleaner not carb cleaner and spray threw out your vacumm hoses it will idle up or choke out when you hit the hot spot for the leak im almost willing to bet you have a vaccum leak that whats causing your check engine light but however you have an upper hand for have a check engine light on thats the way your car is talking to you so dont ignore it take it in and have it scanned also because you have gm product it sets hard codes so have them pull all codes not just the current codes

Timing belt/chain may have been put it slightly off time, when motor rebuild

no fan comes on when engine cold start up .but it will come on when you turn on air conditioning or defrost on .if engine idling a while when temp get 190 degree the fan will kick on.if over heating you got air in system .wait until cools check coolant add more .crank engine let it idle few. minutes when start warming up turn off engine wait a while before removing radiator cap so you wont get scald.add more coolant .crank it again starting warming up turn off engine wait a while .add coolant .keep doing this procedure until your coolant stop dropping off .if you do this more than 6 times you got a leak some where.check crank level for signs.if oil level higher than normal.if everything looking good.when engine cool make sure add coolant to over flow jug cold level mark.