Heater not blowing heat

Hello

Is the vehicle reaching normal operating temperature on the dash gauge?

You do have plenty of coolant¦..(just asking so we are on the same page) Why did you change the core? Most likely based on what you are saying there is either air in the system or your water pump is not circulating very well, but that would also affect the temp of the vehicle. I have also seen where the fitting on the engine going to the heater hose plug up I would remove the hose then start the engine for a seconds to see if coolant shoots out.

Here is a guide that can help

https://www.2carpros.com/articles/car-heater-not-working

Try disconnecting the return heater hose slightly to release any air in the core. Some have had to back flush the core to get the air out

Please let me know about the operating temp of the vehicle.

OK, well i changed the core out because i didnt think it was working,thats what i originally thought the problem was since its an older vehicle,i've back flushed the heater core. i bought new thermostats but the vehicle overheated with the 195f stats in it,so i put the older one its a 180f thermostat and the truck doesnt overheat,but im not sure if its actually reaching proper temp with this thermostat in.

Hello –

Thanks for the info

Well, that doesn’t mean it wasn’t bad……..you are correct on older vehicles that is usually the problem. One way to check is to feel both heater hoses….if one is hot and the other not then no coolant through the core……thus core plugged.

If there was no heat at all and the temp gauge was reading really low, then possibly a thermostat stuck open.

How many miles on the vehicle?

It may be the water pump or the radiator…….if there is not good circulation through the radiator then that can cause the overheat too.

Now, I still think you have air in the system if the vehicle is reaching operating temp….

milage is like 195000, i flushed out the radiator, temp on guage only comes up slightly-not much movement on temperature guage. even when driving it. i've opened radiator cap with heat on high and topped off,doesnt seem to be air in system.
Brand new heater core, only overheats with new thermostat in,which is a 195f thermostat, thats why i put the old one back in -its a 180f thermostat and it doesnt seem to overheat with it in.

Hello –

Did you try opening the return heater hose from the core to see if any coolant was coming out? Again, if your temp is coming up…….then the heater hoses should feel the same as the upper and lower radiator hoses.

Also, I have had several gain in temperature and I had to keep shutting off, bleeding a little, adding a little, sitting the vehicle on a slope etc then finally the temp stabilized and then finally got good heat to the core.

how do i check my water pump to make sure its working properly?

Hello –

Below is what you can check.

Park your car overnight and make sure the pavement underneath is dry. In the morning if the pavement is wet with liquid, you could have a water pump leak.

Grab opposite ends of the water pump pulley and check for "play" (looseness): Try to rock it back and forth. There should be no give. If there is, the bearings are going and it's time to replace the water pump. By the time you can feel play in the water pump pulley, you may also be able to hear the bad bearing when the engine is running - there may be a low-pitched grinding noise coming from the water pump pulley.

Visually check the water pump behind the pulley for signs of a coolant leak. If the water pump gasket is leaking, it must be replaced.

Also vehicles can overheat and or not cool properly.…………

Now at that……..I don’t see that is your problem……the engine temp is okay……it is the heater which leads me back to air in the system.

Have you found anything since our last chat?

well i had one of the heater hoses in the wrong place ,i had it on the radiator and it was suppose to hook up to the water pump, the water pump had a fitting plug in the top of it and had to be replaced with a hose fitting which i did, but after connecting the hose back up and filling the system with coolant, i checked for air in the system,after filling system more and loosening hoses to expel air, i still do not get hot air from the heater, im beginning to think it is the water pump because both heater core hoses are still cold and i just put in a brand new heater core.
The vehicle will not overheat with a 180f thermostat in it,but did seem to before with a 195f thermostat,Do you think it could be the water pump,there's no play in the pulleys and no grinding of berrings?

Hello –

I have seen the propeller shaft so worn it was not circulating water very well but it went with overheating.

When you disconnect the hose at the heater core did you get good water flow or just kind of trickled out?

It may be the water pump but I am not totally sold on that. I am going to ask another moderator to assist to see what they think also.

One way to test for a bad water pump is to squeeze the upper radiator hose when the engine is hot and idling. Careful, because the hose will be HOT! If you do not feel much coolant circulating through the hose when you rev the engine, the pump may be bad. The other cause might be a bad thermostat that is not opening properly (remove and inspect the thermostat), or a clogged radiator.

Hello, I have a 88 silverado that had the same problem! I replaced everything, and when I went to replace the fan and clutch, I found out there were some motors back in 88 and 89 that were counter-rotating motors. after replacing the fan and clutch, I had to also put a waterpump on that is for a counter rotating motor in order to get enough water thru my heater core to actually get some heat! Sounds crazy, but go to Napa and ask if there are counter rotating 5.7 motors in some of the 88 and 89 pickups. Solved my overheating problems and no heat problems when I found out everything was running backwards.

Hey 88 SILVERADO,

Great addition to the thread nice work, please use 2Carpros anytime.

Best, Ken

THE HEAT OUTPUT WAS FINE TILL FRIDAY. I REPLACED THE THERMOSTAT & GASKET, STILL NO HEAT. MY CHILTONS MANUAL SAYS TO INSTALL THE NEW STAT WITH THE SPRING FACING TOWARDS THE UPPER RADIATOR HOSE FLANGE. ANY TRUTH IN THIS ?? THANKS !

yes there is truth in it.

would like you to buy some radiator and coolant system flush and flush out the whole system.

next bleed the system and the heat should be as good as new.

i have an 1989 k1500 having heater problems temp guage goes to about 240 then back down when it goes down i have luke warm air as long as i acclerate if i let off acclerater it get cold again

Make sure the coolant level is full. Check to make sure the thermostat is working properly.

Heater problem
1987 Chevy Truck V8 Four Wheel Drive Automatic 116071 miles
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I have a 87 chevy scottsdale all original. Just bought last week, very well maintained. The heater blows cold air. Replaced thermostat with oem 195 (had 180 in it) and filled all coolant levels. Temp gauge varies between 190 and 210 while running. One heater hose is warm, the other is cold. Mechanic today said the heater hose that goes into the intake manifold has a heater control valve that he suspects is bad, therefore not allowing coolant to circulate and get hot. I also notice with the Radiator cap off, my water level in the radiator goes up and spills out and then way down, instead of continually circulating. Ant thoughts?

Check for the heat control valve as instructed, operate it by hand if you can and see if the other hose warms up, if not the heater core needs flushing or replacement...you may still have a bad tstat...I also have seen waterpumps with impellers so disolved, the circulating power is gone!

My truck is a 3500, with air conditioning. It has the digital dash.
Sometimes I turn truck on first thing and have heat controls set to warm temp and floor heat. The display shows what I want.
As engine gets to normal temperature on gauge. Sometimes I get heat, sometimes no heat. I have turned dash control off and back on and still no heat. Sometimes I turn engine off, and restart, and then I have heat.
I cannot get display new anymore as it is not made.
I put used dash control in, made no difference. When I shut engine off after my trip I always make sure dash display is on high heat,

Hello,

The first thing that comes to mind is the temperature control actuator has gone out. Here is a complete guide on which one it is and how to replace it, here is also a guide on checking the heater out.

https://www.2carpros.com/articles/replace-blend-door-motor

and

https://www.2carpros.com/articles/car-heater-not-working

Please let us know what you find ;)

Cheers, Ken

Heater problem
1992 Chevy Truck V8 Four Wheel Drive Automatic

no heat. fluids up in resavoir. new thermastat 195. Hot guage isa little higher than usual but not much. heat comes a bit then it blows cold

[quote:81c8f840e1="vinet"]Heater problem
1992 Chevy Truck V8 Four Wheel Drive Automatic

no heat. fluids up in resavoir. new thermastat 195. Hot guage isa little higher than usual but not much. heat comes a bit then it blows cold[/quote:81c8f840e1]

I would say you may have a bad thermostat, they have been known to sell bad ones from time to time. You can check it by placing it in a cup of water that is at the temp of the rating of the thermostat.
If it is a 195 degree thermostat, place it in a glass container of 195 degree water and see if it opens, then cool it and see if it closes .
If the thermostat is good you could either have vapor lock in the cooiling system, a blocked heater core or possibly a lazy water pump.

My heat is only blowing cold, does not matter the setting. I replaced the thermostat (works), I flushed the heater core, topped fluid and removed any air in the system. I pulled the actuator which does work off and manually moved the arms for the vents and still it just blows cold. So the heater core in feed and out are both hot, thermostat works, actuator is working and the fluid is topped with no air leaks, but still no heat. What do I do next?

check for a broken heater cable which controls the heat. it can be broken or the lever is broken/door etc. See picture.

Heater problem
1993 Chevy Truck 6 cyl Two Wheel Drive Automatic 162000 miles

my brother and i changed the thermostat and the
water pump but its a rebuild we have changed the
heater core and put new intake manifold gaskets in
and still have no heat please help

Hi:
With the engine hot, running, and the heater on, do both heater core hoses get hot?

Possibly hoses are crossed and fluid is not passing through the heater core?

Engine Cooling problem
1987 Chevy Truck V8 Two Wheel Drive Automatic 99,000 miles

iI have new radiator,heater core,water pump,and thermostat, and intake gasket was replaced a few months back, i am getting only luke warm air when i turn on the heater,also the radiator cap is new. the tenp gauge barely makes it to the quarter mark. Need Help! what would cause heat not to work?

Are the radiator hoses getting hot? Are both the heater hoses hot, with the controls turned on. engine warmed-up?

Is there good circulation through the heater hoses?

I just did thermostat and heater core and i am getting luke warm heat what could be going on here? Blend door is opening and closing as it should i checked that when i did heater core. I cant figire out what to check or do next.

see if both heater hoses are hot they may not be. if they are both hot check for a broken cable for temp also check for a water valve on engine, been a long time for me I forgot if they have them. then have radiator cap pressure checked it may be part of cause not letting engine build up pressure.

Heater problem
1977 Chevy Truck V8 Four Wheel Drive Manual

We replaced the thermastat first and it did not help .So we replaced the heater core in our pickup because the heat was not getting hot. It did not help at all or actual made it worse. Any suggestions?

Hi:
Is the blend door working (near core)? Also, with the engine hot and the heat on, do both heater core hoses get hot?

Joe

Heater problem
1979 Chevy Truck V8 Four Wheel Drive Automatic N/A miles

hello

my truck is having trouble with the heater it works just enough to defrost the windows some times ive already flushed out the lines ,no leaks, and replaced all the hoses and still isn't putting out enough heat what else could be the problem

My first guess would be the heater control valve.
I would by-pass it by using a piece of tubing or a deep socket that fits the ID of the hose and some hose clamps.

If that works, its a control valve not working. Be it the valve or what ever controls the valve ie heater controls inside the cab.

David

[quote:8414da9648="DCS1998"]My first guess would be the heater control valve.
I would by-pass it by using a piece of tubing or a deep socket that fits the ID of the hose and some hose clamps.

If that works, its a control valve not working. Be it the valve or what ever controls the valve ie heater controls inside the cab.

David[/quote:8414da9648]

that means the whole dash would have to be removed right

[quote:e9c766723f="SPC.johnson"][quote:e9c766723f="DCS1998"]My first guess would be the heater control valve.
I would by-pass it by using a piece of tubing or a deep socket that fits the ID of the hose and some hose clamps.

If that works, its a control valve not working. Be it the valve or what ever controls the valve ie heater controls inside the cab.

David[/quote:e9c766723f]

that means the whole dash would have to be removed right[/quote:e9c766723f]

Best I remeber, the heater control valve on that modle is under the hood. Attached to the intake.

David