I noticed overheating, no warm air when heat was turn on. ? is the t-stat stuck close or water pump gone? checked hoses in and out of the heater core from under the hood and they were not hot nor felt like any presure while running..

If the heater core hoses are hot but there is no heat coming out of the vents, and the vehicle is also overheating, there are several possible issues that could be causing this problem. Here are a few things to check:

1. Coolant level: Check the coolant level in the radiator and reservoir. If the level is low, it could cause both the overheating and lack of heat. Top up the coolant to the correct level and check for leaks.
2. Thermostat: If the thermostat is stuck closed, it could be preventing coolant from circulating through the engine and into the heater core. This could cause both the overheating and lack of heat. Consider replacing the thermostat if it is found to be faulty.
3. Water pump: The water pump circulates coolant through the engine and heater core. If the water pump is not working properly, it could be causing both the overheating and lack of heat. A mechanic can test the water pump to determine if it is functioning correctly.
4. Heater core blockage: If the heater core is clogged or blocked with debris, it can prevent hot air from circulating through the cabin. This could cause a lack of heat. Flushing the heater core may help remove any blockages.
5. Cooling system blockage: A blockage in the cooling system, such as a clogged radiator or hose, can prevent coolant from flowing properly and cause overheating. Have a mechanic inspect the cooling system to determine if a blockage is present.

These are just a few possible causes of the overheating and lack of heat. It is recommended to have a qualified mechanic inspect the vehicle to diagnose and repair the issue.

Couple of thoughts. are you losing water/antifreeze, do you have the right mixture 50/50 water/antifreeze. You did not say if the thermostat is removed or replaced. If thermostat is stuck closed water will no circulate. Are you getting any flow from the water pump. If your heater core is bypassed you should not get any hot air from the heater in the vehicle. Make sure your oil levels are good.
https://www.dummies.com/home-garden/car-repair/heating-cooling-system/how-to-troubleshoot-an-overheating-engine/
https://www.thoughtco.com/figure-out-why-your-car-is-overheating-281320

High high does the gauge go up? mid way, 3/4 way? That would be normal. The thermostat opening temperature is about 195-205 degrees. If you are not getting heat from the heater then you may have a plugged heater hose or a plugged heater core. To check the heater system, while the engine is running and warmed up, touch the heater hoses to see if they get hot. If they are hot to the touch then water is flowing through the heater. Also make sure that you bleed the cooling system correctly . There should be 2 air bleed ports in the cooling system. One by the t-stat housing and the other above the water pump area.

Could be a clogged heater-core, or it could be a bad thermostat. Waterpumps hardly ever fail, unless it is leaking. The pump mechanism is direct-drive, so if it is turning, it is working...
Try checking the thermostat in a pan of water, on the stove, with a thermometer to see when (IF) it opens. If it's NOT the thermostat try flushing the heater-core (buy a kit and use a garden hose).

Both of the hoses at the heater core should be hot. If one is cold the heater core is plugged. You can think of it this way. If the thermostat was stuck closed and you checked the upper and lower radiator hoses with the engine hot the upper hose would be hot and the lower hose would be cool because there is no flow. If you check the hoses with a properly working t-stat both hoses will be hot when the t-stat is open and coolant is flowing. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

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

1. if your thermostat is going out...you will generally over heat if its stuck in the closed position....initially you might not even notice.but watch your temp gage.

2. If sticking in the open position..rare... your car will require a longer warm up period...operating temp.....heater takes longer to heat up...tough to check in the summer time...if you think its going out then just replace it and be sure to install the new gasket that should come with it....they are cheap and one of the easiest things to fix on a motor...failure to fix it can result in an overheated engine, oil breakdown and seized engine parts

3. Water Pump.
Listen for a faint ( initially ) metal on metal sound from the front of your motor.... easiest thing is to take a cut off broom handle...solid wood....place it on a section of the pump where you won't get hit by the belt or fan blade...then place the stick against your ear and listen...you will hear a faint smooth grinding sound...thats the bearings...if its chattering or very loud, then you have a pump going bad...also just before they go out you should see water dripping from the bottom of the pump or engine, near the pumps location.
You can buy stethoscopes and use water hose etc to check it but the wooden handle is the cheapest.

UNHOOK BOTH HEATER HOSES AND FLUSH OUT HEATER CORE
DO IT FOWARD AND BACK FLUSH / COVER DIST. CAP OR YOU WILL
FILL IT WITH WATER / IF IT CLEARS OUT HOOK HOSES BACK UP AND
BLEED AIR OUT OF SYSTEM / IF IT DOES'T CLEAR OUT HEATER CORE
WILL NEED TO BE REPLACED (DASH COMES OUT TO DO HEATER CORE)

The feature than can determine the way the pump turns would be whether they were driven by the smooth side of a serpentine belt on the one had, vs. the grooved side of a serpentine belt or a V belt on the other hand.

It would really be a good idea to get a numeric reading on the engine temperature...

Of course, the number one issue is the thermostat. If it is too high of a range, or is not opening properly, the 4-core radiator will never be called on.

Next is the possibility that steam/vapor is collecting around the t-stat. I had a big problem with that in an Aries K. Once it got hot enough to open the t-stat a few times the temperature settled down.

If the fan is not doing its job sufficiently you will get overheating at stop lights and in crawling traffic, but cooling that is fine above maybe 15 or 20 MPH.

If the bottom radiator hose has failed, it can collapse due to the suction of the water pump. For the whole length of that hose you should not be able to flatten the hose by hand. It should have a spiral of wire, a "spring," inside it that prevents that. If that wire has corroded, and isn't doing its job you can get compromised flow.

When the engine is cold, start it up. Before long, the heater hose that comes out neat the t-stat should start to warm up, while the upper radiator hose stays cold. The closed t-stat forces circulation through the heater system. This causes flow over the hot surfaces, and carries the heat from the area of the cylinders to the area of the t-stat. without that, the water's heat would take 10's of minuted to get to the t-stat.

Next, when the heater hoses get too hot to touch comfortably, but before the engine overheats, the upper radiator hose should start to warm up. The t-stat will start to open, and a little hot water will sneak out of the engine, heating the hose a little. That will introduce a little cold water from the radiator into the water pump, where it will get quickly mixed with the water circulating through the heater system, closing the t-stat pretty quickly. So the initial warming of the upper radiator hose will be pretty slow.

If it overheats before the upper hose gets too hot to touch, you have a t-stat problem. Either the t-stat is failing to do its job, or it is not getting the heat signal it needs to operate properly.

If the heater system is clogged or plumbed wrong, it will not allow the requisite circulation.

I hope this gets you on the road to fixing your overheating problem. A 302 with a mondo radiator as you describe should have no overheating troubles, even in the desert!

Unless you have symptoms of over-heating, I rather doubt that your water pump is a problem. I recall that my water pump had a metal impeller (1992 C900); I haven't heard of a plastic impeller on a Saab pump before. (Most pump failures are the bearing seal, and the pump leaks coolant) If your temp gauge is slightly low (and was OK before) I'd rule out water pump issues.

You might have one or more of the following issues:

1. did you use a Saab thermostat? The Saab stat has three stages (no flow to rad - cold; flow to rad and heater core - normal operation; and no flow to heater core, full flow to rad - overheating) that most after market stats don't.
2. did you use a low temp stat? this opens at about 82 deg (rather than 89 deg), and will run cooler during the winter, hence you gauge will show lower than the mid point. The big benefit is that your engine won't overheat during the summer (a very good thing!) with the low temp stat.
3. has your rad and heater core been flushed recently? If the heater core is obstructed flow will be reduced and the heater will run cool. Feel the rad and heater hoses when your engine is warm; if heater hose is much cooler than rad hose with heater temp set to max, then core flow is likely restricted, or valve is not moving much from the shut position.
4. is you vacuum tank properly connected and are there no leaks in the vacuum piping? The tank is in the driver side rear wheel well below the trunk deck on a convertible, and in the passenger side front fender area on the other cars. It's a white bottle with one or two hoses connected to it. If not properly on, your vacuum operated heater flaps won't move. Does the air distribution knob make sucking or hissing noises when you set it to different positions? If not, check the tank connections, look for vacuum line leaks, then suspect the vacuum valve behind the distribution knob.
5. Lastly, the shaft connecting the temp control knob to the valve behind it may not be properly in place. This can be inspected, and adjusted if necessary, from the speaker/vent cutout on top of the dash. Make sure you re-connect the black flex hose to the air vent tube, or you'll get no defrosting afterwards!
6. remember, the centre vents always blow cold air; a brilliant idea from Saab so the driver (and passenger) can get fresh air in the face and stay awake while the rest of the driver, passenger and car is toasty!
7. see http://townsendimports.com/Web/cooling_system_folder/thermostatreplacement.htm for flushing and stat replacement info
   

hello.....
first in this problem you need to look for cheapest things to do which is start with you thermostat abd make sure its open and close by how much temp inside the eng. then u need to feel the input hose and the output hose which they come from the heater core they should have closely same temp . if there is non of them have any heat thats mean the water pump blower is broke and u have to replace the water pump, if one of the heater core hose hot and the other cold the problem in the heater core , about the A/C light is on the A/C comprasser shoul work with the heat becuase hot air + cold air = dry air which u need for ur front DEF