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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: 78ScottsdaleK20 on November 19, 2006, 10:21:00 pm

Title: Heat not Heating
Post by: 78ScottsdaleK20 on November 19, 2006, 10:21:00 pm

First time to the site. Didnt know there were this many people with classics. Great site! I have a 78 Scottsdale K20 with a 350 no A/C. The heater does not blow very warm air. I just finished putting in a new 195 degree thermo and it got a lot better, but I would call the temp of the air to be barely warm. It blows hotter when stationary, but cooler while driving. Could this be from an air bubble in the system? I imagine a clogged heater core would react the same way...saorry to say if I have to pull tha thing. Thanks for taking time to look and any advice is apreciated.
Mike <p></p><i></i>

Title: Re: Heat not Heating
Post by: Lt.Del on November 19, 2006, 11:43:00 pm

There are a few things you can check.  The heater system is really quite simple.

First, when engine is warm, check to see if BOTH lines in the firewall (input and outgoing of the core) are warm or hot to touch. If both are hot, core is not clogged.  The coolant is going in (one hose hot) and coming back out (second hose hot).

If only one hose is hot, core is clogged.  Get an old garden hose (or and old washing machine hose--cut one end off--hook the washing machine hose to your garden hose) and attach the cut end of the hose to your core hose---you can unhook both lines going into your firewall where they attach to you enginer (intake). Get a two inch piece of copper line or other little tube to hook the garden hose to the core hose.  
Unleash the dam!!  See if junk gets spurted out the other line.
If you use an air compressor, do not use too much pressure--maybe 40psi max...you can damage your core and end up with a lake on your floorboard.

If core is not clogged (both lines hot), your heater doors (flaps) are not opening/closing correctly.  cables attach to these doors to open defrost, heat, vent, etc....

You mentioned you replaced your thermostadt, therefore, i dont think it would be the coolant not getting hot enough---that should be fine.  Is your temp sensor guage coming off the lowest setting after 10 minutes of running?  If it moves suddenly, that is when your thermostadt opens and all is working well there.   You mentioned it gets warmer when you are idling at a stop....that is because no cold air is forced through the radiator to engine and it should be warmer.  You can always do the old school bus trick and put some cardboard in front of the radiator in your grille.  That'll get her warmer.

I dont thing air bubbles are a problem as long as your coolant level is fine and your radiator cap is relativley new......people often overlook replacing radiator caps w/ normal preventative maintenance....they have a spring coil that opens up when it gets too hot (lots of pressure) to let off steam/coolant into your resevoir. Replace your cap atleast once every other year or when having troubles with coolant level/heating system.

hope this helps



 

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

Title: Heater not Heating
Post by: 78ScottsdaleK20 on November 20, 2006, 01:53:00 pm

Thanks for the tips Andy! I will try your trick of flushing the core. I did do a weak flush of the system. I have to remember the truck is almost thirty years old, and the heater core is probably stock. I should just replace it before it blows and I have a huge mess to clean.

See ya for now.
Mike

Title: Re: Heater not Heating
Post by: DnStClr on November 23, 2006, 12:29:00 am

Hi Mike. Welcome to the site from Tennessee.  

Don St.Clair
Culleoka Tn

Title: Re: Heat not Heating...found a ring though
Post by: 78ScottsdaleK20 on November 24, 2006, 09:36:00 pm

I pulled the heater venting assembly with the heater core and found the reason the temperature control lever was not going all the way to the right, was interference from many .30-.06 bullets, pens, screws, and even a ring...too bad it isnt worth anything

I re-installed everything after thoroughly checking the heater core over and lol-and behold I have super hot air from the heater, with the help of the installation of a 195 thermo.

The big push for this...the forecast for the coming week...single digits for the high

Thanks for those of you who replied with suggestions and tips.

Keep on truckin
Mike

Title: Re: Heat not Heating
Post by: PromiseKeeper on November 10, 2011, 08:42:52 am

I have very little heat coming out of mine... non A/C.... new radiator, heater core, 195 thermostat, heater hoses, and the flappers seem to be working fine. I disconnected them and worked them by hand to confirm. I know this isnt rocket science, but what am I overlooking?

Title: Re: Heat not Heating
Post by: bake74 on November 10, 2011, 10:45:46 am

     Did you do like sarg suggested and see if incoming and outgoing of heater core hoses were hot ?  If not try what he said with the garden hose.

Title: Re: Heat not Heating
Post by: PromiseKeeper on November 10, 2011, 11:32:15 am

Bake,
Everything is new, so I'm pretty sure there are no blockages. The hoses are all the same temp... warm. There is pressure on the cap when it's at operating temp so I'm thinking it must be OK too? The only thing I can think of is the heater hose configuration, which I did according to advice on here. One of them goes to the intake manifold and the other to the water pump. When I put the new radiator in, I asked on here if one had to go to it and the consensus was "no" You can see in my original post everything I replaced. I know it's something simple..... but it's making ME simple! LOL  Thanks!

Title: Re: Heat not Heating
Post by: Captkaos on November 10, 2011, 03:16:43 pm

As long as the 2 hoses are on the opposite "sides" of the flow you should be ok.  Is the fan blowing, but it is just cold?

Title: Re: Heat not Heating
Post by: PromiseKeeper on November 11, 2011, 09:53:06 am

Correct, Captain. I double and triple checked how the hoses are run. Everything is new with the exception of the radiator cap. Flappers all work correctly. It seems like I'm not getting engine heat for some reason. Times like this, I wish it had gauges. At work today, I'm going to get a good reading on temps. The mechanic there has a laser thermometer and I'll get some readings from each hose before I shut if off. And yes, blower is working. Getting luke warm air at best. i live about 5-6 miles from work.... it should be up to temp by then.

Title: Re: Heat not Heating
Post by: Captkaos on November 11, 2011, 11:53:56 am

You have a Thermostat in it right. 
My Suburban that I started driving more last year (now daily) was horrible in the winter.  No heat at all.  I finally decided to replace the thermostat thinking it was stuck open since water was moving in the radiator all the time.  When I pulled it off, there wasn't a thermostat in there...

Title: Re: Heat not Heating
Post by: PromiseKeeper on November 14, 2011, 08:57:44 am

Capt,
Yep, replaced the stat last week with a new 195. The only thing left is the radiator cap, found the old one wasn't holding pressure. If that doesn't do it, I'm at a total loss. EVERYTHING has been replaced. I checked the hoses with a laser thermometer after driving about 6 miles. Both heater hoses were about 135. Top radiator hose was about 90 near the radiator. The thermostat housing read about 180 and the bottom hose was about 70. It doesn't have a gauge so that is about the best I can do to get an idea. That seems to be a bit cool dint you think? It almost seems like maybe a bad stat stuck open?? The radiator is level full, but there didn't seem to be any movement of water when I had it off.

Title: Re: Heat not Heating
Post by: PromiseKeeper on November 07, 2012, 09:05:25 pm

Well, I put this off all summer since I didn't need the heat. Like I said before....everything was replaced. Both heater hoses are very warm so I'm convinced the water is flowing thru them. I even got under the dash and checked to see that the cables were working properly. It's almost as if there is a flapper door not opening or something. The cable works freely and the arm on the heater box moves. Is there something I could have messed up when I had the heater box off to replace the heater core? This system is pretty straight forward yet I can't get heat!

Title: Re: Heat not Heating
Post by: frotosride on November 13, 2012, 10:44:29 am

Pk, you may not wanna hear this but it's not as bad as it seems or that hard to do. The cables and the arms that open and close the flappers may operate from the out side fine but the flapper it's self can be stuck or broke. You will have to take the heater hoses,blower fan and vaccum hoses off to get the air box out and check the flappers. The one that controls the air flow from heater core to a/c or vent is only held in by a small metal rod and it may have to be glued/bonded to the rod as they can strip causing the rod to move and not the flapper. Mine was broke as I noticed when I replaced my leaking heater core. Hope it's not to cold out when you start this but with in an hour you should be buttoning it all up. Oh and check for leaks on the vaccum accuators when you remeove the box. I just used a syrenge to pull a vaccum and watched it to make sure the rods moved appropriately.

Title: Re: Heat not Heating
Post by: PromiseKeeper on November 13, 2012, 04:33:55 pm

Thanks frotosride. That will probably be the next step. I don't drive it in the salt so it will get put away pretty soon. I have access to a heated garage this winter so this will be one of those snowy day  projects. I don't have A/C so for this project, that is a plus. Everything is cable operated so no vacuum lines to worry about.