No heat from heater on 01 sonoma x cab

when vehicles get this old and maybe there fluids havent been kept perfect over the years then yes due to sedaments in the cooliing fluid the heat core tends not to get as hot as it did when new , you can try a coolant flush , run heater while proforming a "hot" flush but do use all the normal precausions when dealing with hot engines

normally the radiator will purge itself as long as the overflow jug remains at the recommended level. warm eng to normal operating temp if you have no leaks it should draw water as needed from the overflow jug when you shut the eng off .. it may take a few times of starting and stopping eng but this method does work.. careful as the radiator fluid is very HOT !!! if no overflow jug is in your system go to highest rad. hose and open the system there.only do this when eng is cool. slowly fill radiator at the cap holding the hose you remove higher than the cap. a helper is needed for this procedure. starting at btm rad hose gently squeeze entire length of hose working your way to the next lowest hose do the same procedure for each hose. heater hoses also need be done reattach hose start eng let idle till normal operatin temp is reached turn heater to full heat . let eng cool then chk level of rad. repeat as needed. good luck .TIP : be patient .

I would suggest jacking the front of the vehicle as high as you can to get the trapped air in heater core out through the system and thats the only way I know of doing it air will rise to highest spot (radiator) when it is jacked up higher than heater core..........Providing you hooked up your heater hoses the way they were when you took apart.

these trucks are famous for plugged heatercores,what you do is,remove both hoses to heatercore at firewall, mark there location, next cut two peices of heater hose, about 12 inches long, slide on the heatercore where the hoses where, then use a water hose and flush in both directions a few times, then you should have heat, also if its been a while i would also have the cooling system flushed out, hope this helps. good luck.

As soon as the vehicle reaches around 180/195 (depends on the temp of the t-stat) the thermostat should open and thereby filling the top hose with warm/hot water.
Are you sure the thermostat is facing the right direction? Is the cooling system full?
Here is what you can do: remove the t-stat, replace any lost coolant/water and run the vehicle with heater on full blast for about 15 minutes or until the temp gauge is showing about halfway. During this time be sure to monitor the coolant level in the reservoir.
If you still have no hot air you may have a blockage or perhaps the heater hoses are not even connected.

You just might have an air lock. Try bleeding the system from the heater hose at the firewall. Losen one hose a little, and at operating temp. open slightly to let air out. You will lose some coolant, but just refill the rad. Now, both hoses should get hot.

opps clicked clarification .... -- run your engine up to operating temp . shut off engine and check your radiator by placing your hand on top - middle - and bottom, they should be the same temp , if not your radiator is plugged... (be careful not to burn yourself) .... also grab the heater hoses going through the firewall, if they are not the same temp feel you may also have a blocked heater core.

that year / series of GM sonoma and s-10 where famous for having clogged heater cores - is temp of hoses going in and out the same ? if not try to flush out ther core, if they are, ck to see if the hot water valve is woking, and finally operation of the doors inside the heater box itself

Ck Eng light probably not related.
The heater core is clogged. A bottle of cooling system "quick flush" may be all you need ($6 AutoZone).
There is also a complete flush system, but requires that you splice into the heater hose (I installed it on my Taurus - works great!).

By the way, there is a heater core bypass hose. It is connected to the two heater core hoses near the firewall. You may want to remove the two "Tee" fittings and use a 5/8" hose splicer so that the flush passes through the heater core at full force. Put the Tee's back in place after the flush.

If you remove the tee fittings and don't flush, the heater will work, but the core may eventually start leaking.

Hey iisha, although obvious, 1st thing to check is the coolant level. If it's low, the engine will run hot and the low level prevents coolant from circulating to the heater core inside the car, so the result is little or no heat, but engine running hot situation. The top rad. hose takes hot coolant from the engine, it flows down thru the radiator where it is cooled (w/ help from the fan) and the coolant returns to the engine at a reduced temp. to keep the temp under control, and it's returned thru the bottom hose (the result is the bottom hose should be cooler thant the top. There's more involved than that, so 1st check your coolant level, if it's ok let me know I'll help further. Hopefully the fix is that simple, and it is a rather common problem.