74 Crewcab Heater core Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

MudBug · 03-12-2011, 06:13 PM

I've been asked to help a friend change the heater core in a 74 CrewCab.Does the box the core is installed in come out the bottom of the dash or is there another way to replace it? This is my first heater core replacement in this body style truck so any help would be greatfull. Thanks

tucsonjwt · 03-12-2011, 07:05 PM

Don't know about crew cabs, but on the three regular cab squares I have owned, all the heater cores came out from the inside. If you can get your hands on a Haynes or Chilton manual it will help. You remove the duct from the inside and the heater core is strapped inside. So, disconnect the heater hoses, catch the coolant in a pan, disconnect wiring, remove nuts from around the blower housing, GENTLY remove the duct from the inside, remove the heater core from the straps and replace with the new heater core, reinstall the duct, connect the heater hoses, top off the coolant, enjoy heat.
Make sure you use a copper heater core - don't get an aluminum one.
If you have A/C on the truck, then you have to "feel" for the nuts under the blower housing because they are not easily visible, and the reinstall is a wiggle this way, wiggle that way affair. I used a mini socket with u-joint attachments and an inspection mirror and a scratch awl to find the holes. If you don't have these, see if you can borrow them. You can buy an inspection mirror for $2-$3 at Harbor Freight - excellent investment.
I stress - do everything gently. The plastic housings can crack easily on these old trucks, and the heater core can leak if you break the solder joints with rough handling. On the bright side, shop labor for this job is about $250, so it is always worth a shot to try it yourself.

Benelli · 03-12-2011, 07:28 PM

Take it easy on things, make sure that if it comes with foam in the package to use it with the instal by wrapping it around.

alum. ones suck, I have one and it doens't even compare to the old copper core.

tucsonjwt · 03-12-2011, 07:37 PM

Yeah, if the insulation is shot (most likely), then get some foam insulation to match it from the hardware store.

MudBug · 03-13-2011, 09:58 AM

Thanks for the replys. The Crewcab was a heat only tuck until somebody put an add on a/c package on it.
Thanks

03-12-2011, 06:13 PM	#1
MudBug Registered User Join Date: Jan 2007 Location: tennessee Posts: 159	74 Crewcab Heater core Question I've been asked to help a friend change the heater core in a 74 CrewCab.Does the box the core is installed in come out the bottom of the dash or is there another way to replace it? This is my first heater core replacement in this body style truck so any help would be greatfull. Thanks

03-12-2011, 07:05 PM	#2
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,188	Re: 74 Crewcab Heater core Question Don't know about crew cabs, but on the three regular cab squares I have owned, all the heater cores came out from the inside. If you can get your hands on a Haynes or Chilton manual it will help. You remove the duct from the inside and the heater core is strapped inside. So, disconnect the heater hoses, catch the coolant in a pan, disconnect wiring, remove nuts from around the blower housing, GENTLY remove the duct from the inside, remove the heater core from the straps and replace with the new heater core, reinstall the duct, connect the heater hoses, top off the coolant, enjoy heat. Make sure you use a copper heater core - don't get an aluminum one. If you have A/C on the truck, then you have to "feel" for the nuts under the blower housing because they are not easily visible, and the reinstall is a wiggle this way, wiggle that way affair. I used a mini socket with u-joint attachments and an inspection mirror and a scratch awl to find the holes. If you don't have these, see if you can borrow them. You can buy an inspection mirror for $2-$3 at Harbor Freight - excellent investment. I stress - do everything gently. The plastic housings can crack easily on these old trucks, and the heater core can leak if you break the solder joints with rough handling. On the bright side, shop labor for this job is about $250, so it is always worth a shot to try it yourself.

03-12-2011, 07:28 PM	#3
Benelli Watchin the rust grow Join Date: Oct 2008 Location: Western Nebraska Posts: 950	Re: 74 Crewcab Heater core Question Take it easy on things, make sure that if it comes with foam in the package to use it with the instal by wrapping it around. alum. ones suck, I have one and it doens't even compare to the old copper core. __________________ 1979 Chevy K10 (H/D Front end) - 350 w/ Holley Truck Avenger, Weinald Intake manifold, headers, bored .060 over, mild cam, Built up TH350 (TranStar Shift kit) with a part-timed NP203 t-case SOLD ($3,000) 1997 Chevy Silverado 1500 - 4.3 vortec, extended cab, 21 highway MPG, stock. "Red" SOLD ($3,000) 1987 Toyota 4wd Pick-up - work in progress, future DD SOLD ($1,850) 1998 Dodge Ram 2500 Cummins 5spd Quad cab - old 12 valve with some work done 2004 Chevy Silverado - Black, 4x4, 5.3L, stock for now Underneath that rust is a heart of gold

03-12-2011, 07:37 PM	#4
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,188	Re: 74 Crewcab Heater core Question Yeah, if the insulation is shot (most likely), then get some foam insulation to match it from the hardware store. Last edited by tucsonjwt; 03-12-2011 at 07:43 PM.

03-13-2011, 09:58 AM	#5
MudBug Registered User Join Date: Jan 2007 Location: tennessee Posts: 159	Re: 74 Crewcab Heater core Question Thanks for the replys. The Crewcab was a heat only tuck until somebody put an add on a/c package on it. Thanks



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