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alaskanspear
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Dec 19, 2012, 9:48 PM
Post #1 of 12
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No Heat!! HELP ME PLEASE
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1998 Chevy 1500 5.7 V8
I have no heat coming through the vents. Air blows just fine through all vents, I am able to switch between defrost, floor... ETC. Just no heat.
I replaced the thermostat last night thinking that could be it, but no go. Any ideas??? I was thinking about trying to flush the heater core, but I dont know how hard that is, someone said I could do it without removing it.. I tried to feel the in/out hoses in the engine compartment to make sure they are both hot.. but they are really hard to access and they have a foam shield over them. Coolent levels air fine
Please help.. I live in Alaska and its -10 right now.
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Tom Greenleaf
Ultimate Carjunky
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Dec 19, 2012, 10:18 PM
Post #2 of 12
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Re: No Heat!! HELP ME PLEASE
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Never had one apart and just looked at a '97 for what is where for the ones with A/C. Both hoses hot but no heat. There has to be a "blend" door as my own doesn't regulate temp by water flow. Both hoses warm to hot doesn't suggest plugged heater core so fast. It will be if the Vortec 5.7 a pest to flush it out as the fitting of return heater hose has a dumb-arse fitting on engine, not just a clamp there. Bet it will break if old and untouched.
Clamps at the core itself will be a hassle. Should use the exact right tool and GO EASY IF YOU REMOVE THOSE HOSES or you will snap the necks off of the heater core that you probably don't need just yet.
I can try to look for info on where actuator for blend door is for temp but will need to know if A/C equipped or not - not if that works just if it has it or not.
One more - does the temp dial on dash seem stripped out? None I know of give a feeling of doing much but it that thinks it's on full cool air setting it could be the trouble??
Actuator for where air flows is over gas pedal. I don't think that is temp controlling but might be. Wrong location I would think for temp control but will check if you just say this came with A/C or not,
T
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alaskanspear
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Dec 19, 2012, 10:27 PM
Post #3 of 12
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Re: No Heat!! HELP ME PLEASE
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It does have AC, it seems to be working fine. . Temp gaige on dash seems normal as well.
(This post was edited by alaskanspear on Dec 19, 2012, 10:30 PM)
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Tom Greenleaf
Ultimate Carjunky
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Dec 19, 2012, 11:18 PM
Post #4 of 12
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Re: No Heat!! HELP ME PLEASE
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I just lost a post in here and looked again at my own '97 C/K 2500 all HD. Parts said this uses a vacuum operated heater control valve. It would look like this is this shows........
(won't show) An "H" like thing in line with heater hoses. My own doesn't have this but could see an electric actuator looking up on passenger's side, hard to see but there was the tell-tale small alloy gear end of what must control the temp of air. You would need someone to change temp request and see if that moves. Like all these underdash things are a pest to get at and if it doesn't move it doesn't mean it's broken quite yet. It could just be stuck.
Wild guess as I have done any dash diving into this thing but bet you could get near that door with the blower motor removed.
Back one - A/C working in season means nothing right now @ -10F. That just changes the layout of the system. See what you can see or if you can hear a slipping gear right there or something.
Not the world with a ton of 1/4 sockets but you would need a warm place to work on this IF THIS IS IN FACT THE PROBLEM SPOT. You should be able to see something going on there. Heat is passing thru the heater core if both hoses are warm/hot.
Awful hard to say but usually a plugged heater core the return hose might be cold. That usually would puff some heat and then go cold. That's the one that returns to intake manifold the hot feed comes right off the water pump or should be that way.
Best I can suggest for now looking right at what should be the same as yours but who knows?
T
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alaskanspear
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Dec 20, 2012, 12:07 AM
Post #5 of 12
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Re: No Heat!! HELP ME PLEASE
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I am sorry but I am not understanding. Am I supposed to be looking for a valve or something, under the dash? It's been really cold up here lately and I let the truck run for 45 minutes... Wouldn't I feel some heat from the vent? Is there a diagram somewhere of that gear you said to check???
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Tom Greenleaf
Ultimate Carjunky
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Dec 20, 2012, 12:55 AM
Post #6 of 12
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Re: No Heat!! HELP ME PLEASE
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That's not the exact one but gives you the idea. See that ~10mm alloy part at the top? That is supposed to turn a flap door in this case called a blend door such that you get air directed thru heater core at assorted amounts from tons to none. That top bit would be seen turning if you changed from coldest to warmest on the dial. It was hard to see by flashlight but where I would expect it to be.
Again - we don't know much yet. If it turns than it might not be turning the door or could be stripped out. Not known is if it gets power to do anything yet.
Knock on wood that so far it hasn't happened to me but some of these will go thru a cycle of their full range if even a battery is disconnected or run too dead and stick the door. Would that break something? Maybe?
Not sure what you will see just looking in your truck. Mine is all HD with no factory air bags from new so easier to see stuff. Not sure if you have a passenger's air bag and stuff in the way for good view.
Another generic pic of what a mess of junk is in the heater/A/C box that we take for granted............
This pic is from an older GM truck with most stuff removed for the view..........
That is where your blower motor is, over gas pedal is the air flow actuator and not shown is the one for blending air temps higher up than the blower shown in that pic.
A blend door is just a flap if you will that might look like this but out of sight..........
I'm long retired. When I needed this junk I went to junkyards where the vehicles were already torn apart for assorted things. A 1998 Full Size GM truck might require dumping whole dash down on the seat to get at some of this stuff!
My guess is if that actuator is the problem it could be done without horrifying digging into other things to get at it. We aren't sure yet but you should be able to see something happening there if it takes dental mirrors.
I'll be offline for a while. It's 2:30 am here in MA and do stay up late but enough for a while.
You just may do better to just explain this problem if you don't have the place and tools to a tech that does this near you and just let them do it. You need the place and plenty of light and hands of a two year old to get at some dashboard crap!
T
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re-tired
Veteran
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Dec 20, 2012, 1:39 AM
Post #7 of 12
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Re: No Heat!! HELP ME PLEASE
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The good news is that tom is correct ., Its most likely the blend door actuator. The bad news is that you must drop steering column and pull dash back to access the actuator.Its the one on the very top in the picture. When you get the act off take a screwdriver and gently turn the door back and forth . If ok replace act.
LIFE'S SHORT GO FISH
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Hammer Time
Ultimate Carjunky
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Dec 20, 2012, 4:02 AM
Post #8 of 12
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Re: No Heat!! HELP ME PLEASE
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Most of the instructions here are based on the fact that it has been verified that both heater hoses are hot and from what i read, this has not been verified yet so my advice is that, before you spend too much time under the dash, verify that both hoses are hot because it is just as possible that you could have a plugged heater core so that needs to be eliminated before diving into the blend door possibilities.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Dec 20, 2012, 6:29 AM
Post #9 of 12
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Re: No Heat!! HELP ME PLEASE
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? He said there was foam making checking hoses tricky to impossible? I haven't seen that on these on heater hoses. You should be able to feel them closer to the engine as these flow all the time not just when heat is requested or temp level adjusted by water flow. That means it is near certain they are part of the by-pass system for coolant all the time.
At super cold temps engine needs to mix coolant inside more than ever. Erratic temps would show without effective bypass so I'm ruling that out with info at hand with this.
Thermostat was replaced with no change so now if not properly full of coolant at radiator heater would suffer. It's cold at said (-10F) and would take ages for thermostat to send any air out radiator, drop level then know it's really full.
Not sure if this person knows that you don't have to dump all coolant to do just the thermostat which is pretty high up.
Other: As cold as that gets if a heater was blasting heat it still isn't enough to cool the engine without radiator which isn't going to get much and temp should stay exactly steady once warmed up.
If this has suffered the dreaded Dexcool Clog up it should show it right at the radiator cap.
Another thought is the heater hose quick connect on engine might be mostly clogged. It looks like this........
Marked "flow" with arrow so that is the line to inlet of heater core. Haven't done my own yet but looking right at it. It has a flow restrictor inside it such that high RPM wouldn't blow too much too fast or over-pressure the core itself. Further away from this that hose should be at engine temp or close and be warming up before thermostat opens.
May be all wrong with something as I just looked again. This goes to the larger hose of the two. Should be one from water pump is inlet line by direction of fan and belt. This engine may be counter rotating! That would mean that part is then the return line. Saw the wiring type insulation but closer to engine behind alternator where too much crap is put into a plastic harness holder right there but you can touch plain hose after that.
This thing shown above with it's restrictor would be a weak link for flow IMO. If this lack of heat happened all at once this cooling system is either full of junk that just moved and clogged things or we are back to that actuator. Can be tested so no mistaken repairs have to happen,
T
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alaskanspear
User
Dec 20, 2012, 6:18 PM
Post #10 of 12
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Re: No Heat!! HELP ME PLEASE
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I bought some radiator flush today and was planning on flushing radiator. Do you think that may help??
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Tom Greenleaf
Ultimate Carjunky
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Dec 20, 2012, 7:44 PM
Post #11 of 12
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Re: No Heat!! HELP ME PLEASE
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May not help but can't hurt. Just know you want to flush entire cooling system and flush heater core both directions. Without some wild antics you won't get all coolant drained so count the listed system capacity and since in AK or anyplace where you can and will see temps below the standard -34F which a 50/50 mix provides you can go a little stronger on the antifreeze %. Even then don't be too excessive with the % of the mix.
This chart shows what you should get with either regular EG (ethylene/glycol) formulas or Dex-Cool which GMs calls for which is marked underhood,
You can see you only need perhaps 60% for much colder freeze protection. NOTE: Even at just -34F protection it will not freeze solid nor expand if exposed to lower temps than that but wont flow and seems nuts but you still need your cooling system if -40F or colder! Keep count and know your protection level. Let it warm up till you feel upper radiator hose get warm which means thermostat has opened letting air out. Shut down and let cool down. This action purges air pocket out to recovery tank and draws back just coolant. Repeat and check at radiator cap which should be left on radiator when running engine and not removed till pressure is gone which you can tell just by squeezing upper radiator hose. DO TAKE ALL CAUTION AS IT CAN BLOW BACK OUT WHEN REMOVING RADIATOR CAP if system has pressure or a hidden hot spot or air pocket.
This fill procedure is critical. Do not allow it to overheat and know it ends up full at the radiator. Clean off cap carefully or replace it with proper rated cap for the truck. This vehicle can be done this way. Some will really want a vacuum fill to know it's full. You just did a thermostat and flushing will work much better with that removed again.
YOU KNOW THIS MAKES A MESS AND READ WARNINGS ON ANTIFREEZE CONTAINERS! It's poison! Do not leave any caught in open containers as animals will try to drink it. It's near impossible but dispose of the wasted product as you can locally and still if not available DO NOT LET THAT RUN DOWN A STORM DRAIN OR AT ANY WATER SOURCE THAT CAN HARM ANYTHING! It will kill plants. Seems harmless but some care handling it helps.
There are better tools than plain pliers to remove hoses/clamps as needed for a good flush. AGAIN - watch out for heater core spouts and radiator spouts if hoses are removed as they can break.
This job as simple as it seems makes a mess. Yes you can do it but consider letting a shop with full equipment just do it. Should not be that expensive and saves that nasty mess,
T
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re-tired
Veteran
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Dec 20, 2012, 11:43 PM
Post #12 of 12
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Re: No Heat!! HELP ME PLEASE
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Try to verify the heater hoses temps Before doing all this . If both hoses checkout hot ,then verify the actuator working or not .With doors shut windows up, turn key to on, but dont start . open glovebox and hold ear to opening. run temp control cold to hot and back several times ,listen for a lite humming sound. if no noise its prob actuator.
LIFE'S SHORT GO FISH
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