HELP: How to change heater core in 84 GMC 3500- no AC

[2badgn]

How difficult is it to change the heater core? I am not that great in mechanical ability with the exception of changing oil, door panels and detailing. I have spent alot of money on this truck and it would be nice if I could change out this heater core myself. The heater core is only about $40.
It was 20 degress in NY yesterday and the heat was minimal on high fan.
Radiator is full, heater hoses were replaced about 5 years ago.

How do I make sure that the problem is the heater core? Truck is 26 years old & it has never been changed. Where is the control valve located?

Is the heater core the box behind the glove compartment?

I have no problems using wrenches & screwdrivers but I struggle w/special clips. Can somebody tell me exactly what is required to remove it.

Thanks
Frank

[lvschevytrucks]

Doesn't sound like a heater core to me, if you have good circulation in your radiator system, and no leaks, Id leave it alone, and look elsewere for the problem

[2badgn]

Originally Posted by lvschevytrucks

Doesn't sound like a heater core to me, if you have good circulation in your radiator system, and no leaks, Id leave it alone.

No leaks, Chevy delaer just changed timing chain, tune-up, complete radiator flush.

Problem is that there is barely any heat.

Any suggestions?

[lvschevytrucks]

what temp thermostat are you running,
Is the fan Blower working,
how well is the cab insolated, any cold air comming in from outside

[thehitchmaster]

If there is no sign of a water leak I would check to make sure the door is opening when you slide the adjuster to hot. If i remember correctly you can see the cable for the door if you take the glove box out.

[2badgn]

Door is opening when i slide lever to hot. Cab is insulated- just replaced the floor jute and vinyl floor matt. Thermostat is factory.

Where is the contol valve?

[old Rusty C10]

this is a picture of the heater box and the cables. Im betting that either the door is stuck or the cable is bad or unhooked the lower cable is the one that opens up the hot and cold door.if you dont have a loss of coolant or you have a decent color of your antifreeze and its not all rusted brown your heater core is prolly not the culprit.
Id crawl under and see if you can open this door and the heat should work

[thehitchmaster]

wow! a heater is a very basic operation. are you reffering to the valve that goes on a heater hose. If so they are usually near the firewall.

[thehitchmaster]

also can you take a air hose and blow one side of the core and make sure its not plugged up. you did say it was pretty old.

[cableguy0]

Do not blow compressed air through the heater especially not an old one unless you want to replace it. it will likely put a hole in it. unhook the heater hoses from the engine and attatch a garden hose to the heater core and flush it backward and forward. its very possible the heater core is clogged. another possibility is a bunch of trash/leaves etc is stuck in the heater box. mice and other critters like to make nests in em which kills the air flow. the door could also be stuck or broken. if there is a heater control valve it is in line in one of the heater hoses.

[thehitchmaster]

not trying to be rude but how would you put a hole in a core by blowing some air in it. Please dont take it the wrong way cableguy, I like your water hose method better anyways.

[2badgn]

Ok- Just started the truck. It was ice cold for several minutes. Then on the highest fan setting, heater and hot, it was a little colder than lukewarm. I got under the dash and heard the flap for the door open and close. When i switched the lever to cold, the heater blew ice cold, and when i switched it back to hot, it was less than lukewarm at its best. Both heater hoses felt warm to the touch.

Truck just got back form the body shop for complete paint and the inner & outer fenders were replaced.
Any other ideas on what to check? How can i make sure than the door is open completely?
Thanks

[cableguy0]

its not meant to take near that kind of pressure. if it is clogged the 100+psi of air is either going to make its own way out of the core or move the blockage. if it cant move the block it will pop one of the solder joints. the most pressure the heater core will ever see in normal use is 15psi depening on the radiator cap and most compressors are capable of 10 times that.

[cableguy0]

if the door is moving at all the arm isnt broke. you wouldnt feel a difference in temperature. is there resistance in the lever when you move it? does it feel like its getting hung up?

[2badgn]

Im thinking its time for a new heater core. Cant run the hose now bc its like 15 degrees in NY.

How many hours of labor could this be?

Im thinking 2 hours plus heater core plus tax.

If it were the summer, I would tackle it myself but its COLD and we need heat. Going to bring it to Chevy tomorrow. Thanks for everyones help.

Frank

[cableguy0]

its not a bad job. its a couple bolts and pretty straight forward especially in a truck with no ac. only one bolt is a pain to get to.

[thehitchmaster]

It took me a couple hours. probably could have done it a little quicker but i used some foam tape to seal up some of those plastic duct connections.

[old Rusty C10]

heater core done in a shop should be about $300-400