1999 chevy s-10 with no heat

put a radiator flush in the expansion bottle run for about 20 miles .that will clean the core of your radiator .and the core of your heating of rust and dirt.you should change your thermostat .after draining it. then refill with 50/50 mix of anti freeze.then put your heating on full .to bleed them both. run the engine on tick over.till water is getting hot .then refit the cap.

disconnect the heat hoses going into fire wall , put hose into one with pressure and flush as it sounds like it could be bloked in the heater core,the other thing that could be the problem be the hot ,cold switch as it restricts the flow to makes the heater hoter or colder , it might need tlc or replacing as it is manaul not elec

Hello! Replace the thermostat, it is defective...I would suggest flushing the cooling system with the heat set to high...Your engine requires Dex-Cool anti-freeze...It, due to electrolysis, has a tendency to "clump" blocking proper flow...Drain the cooling system...Fill with plain water...Allow engine to heat up and when the thermostat opens shut down and drain...Do this three times or until water is clear...Replace thermostat and refill with Dex-Cool...Allow all air to escape before installing cap...

Guru............Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

It could be one of two things.
1. Bad thermostat. Your thermostat is pobably not opening when the engine warms up. Install a new thermostat and you should be OUT OF THE COLD. If not,
2. Your heating core and radiator is probably clogged. One way to solve this is. Flush out your radiator with radiator flush kit. Pease read your owners manual, (YOU NEED TO USE A SPECIAL TYPE OF ANTI FREEZE). If you use the the green color Presotne anti freeze, It will gradually corrode through the linings of your radiator. And the green color prestone anti freeze will blow out the radiator. So read your owners malual ( I beleive it says you have to use Dextron Anti Freeze ( Pink Color).. Replace your thermostat and flush out your radiator. Then refill your radiator with dextron anti freeze. Also make sure the anti freeze resivor is filled to the proper level.. Once you do all of this, YOU DEFFINITLY WILL BE IN HEAT.. YOU CAN DO THIS YOUR SELF ( iT WOULD TAKE ME NO MORE THAN 1 TO 2 HOURSFOR ME TO DO THIS IN MY DRIVEWAY) OR YOU CAN HAVE THIS DONE AT ANY QUICK LUBE LOCATIONS... HAPPY MOTORING

Welcome to FIxYa.com

This is a classic symptom of low coolant level or air in the system. Too, clogged heater core.

Buy a 5 min flush from your local dealer. With a gallon of Anti freeze and water pump lube. Flush the system per instructions on the back of the 5 min flush bottle. And add the one gallon of anti-freeze to system. The top off with water. Make sure engine is running with the heat selector on and fan on high.

See if the will work if not Change thermostat.

Thank you for using FixYa.com

Regards, Lee Davidian

take it to a profetional

first of all, make sure coolant is ok. if ok change thermostat. the reason it does not heat up is that if the thermostat fails it will bypass it. causing it not to heat up! when done if car does not heat up bleed air out of system till you get heat.

Check the thermostat in the cooling circuit for the heat problem; it could be stuck. As for the O2 sensor.....Check the thermostat first. Its cheaper.

sound like you have a bubble in the system. make sure you drain all liquid out, make sure the thermostat is the proper temp rating and is not backwards. Fill the radiator up turn the car on turn the heater on full blast fill up the over flow with anti freeze. put the radiator cap on. watch the temp in the car. dont let it get all the way in the red. you should see the overflow tank start to get the anti freeze sucked out of it don't let run dry. I had this problem with my 2004 dodge ram. This is how a master mech told me to do it

ther are two small tubes that open and close the valve to let in the hot air' one is from right under the carb intake and goes to the right (looking at the engine) right behind the fuse box. if there's o hole in that tube the heat will not work. just change mine becase the tube dry-rotted