heater problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

doughby82 · 12-24-2003, 04:42 PM

ok when i bought my truck it never heated up.i figured it was a thermostat.i changed that and the radiator cap.it gets a little warm but that it.also it starts drippiling out of the radiator overflow,when its running and after i shut it off.any ideas

cdowns · 12-24-2003, 05:17 PM

as far as the little or no heat is concerned a couple of things could be that the valve controling flow thru the heater core is not opening up or the phlenum that holds the heater core is filled with debris loke 30years of pine needles or leaves
as far as the water flowing out the overflow don't fill the radiator when it's cold only fill when the motor is up to operating temp

PanelDeland · 12-24-2003, 05:26 PM

The radiator problem is something a lot of younger guys don't know about.When the engine and radiator heat up the water/coolant expands overfilling the radiator in effect and causing it to run out the overflow.
The later cars used an overflow tank that let the coolant escape to the tank and then it was returned when the engine cooled and created a vacumm.All engines of the non-return line type will use some coolant.They should be filled on ocassion.
You can retro fit a coolant overflow and return easily, if you use the tank from a truck with one or install an aftermarket one.
New cars are required to have them for EPA, as are race cars to prevent wet spots on the track that cause slick spots.

lukecp · 12-24-2003, 07:35 PM

Yes, like cdowns said, the valve controlling heat flow could not be working (assuming this is a non AC truck).

You can look at the flapper valve from inside the cab....it is where the heater control cable goes into the heater box, under the dash in the passenger side footwell. There is a little plastic piece that seals the rectangular hole where the control cable goes in, pop it out and have a look. Make sure the cable is still attached to the lever on the flapper valve, and that it is opening and closing all the way.

If that checks out, you proably have a heater core plugged with pine needles or something. You need to remove it....and proably replace it too. A new core is only around $25, and as long as it is out it would be a good idea to replace it.

nitor · 12-25-2003, 01:28 PM

Yellow72 is right. I just had to replace mine. A/C version. Got it at Autozone. It was about $25.

FRENCHBLUE72 · 12-25-2003, 01:36 PM

Same here I just replaced the core in the blazer and it seem's to blow really hot. I also replaced the fan switch that control's the fan speed .. I never knew there was 3 speed's for the fan..

1969 GMC · 12-25-2003, 05:16 PM

lol! of course they are 3 speeds! mine is:
1). off
2). on but nothing comes out the vents
3). on and air is blowing like a hurricane

12-24-2003, 04:42 PM	#1
doughby82 Registered User Join Date: Mar 2001 Location: springfield ill Posts: 836	heater problems ok when i bought my truck it never heated up.i figured it was a thermostat.i changed that and the radiator cap.it gets a little warm but that it.also it starts drippiling out of the radiator overflow,when its running and after i shut it off.any ideas __________________ springfield illinois 2003 custom (harley)built from scratch 68 swb

12-24-2003, 05:17 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	as far as the little or no heat is concerned a couple of things could be that the valve controling flow thru the heater core is not opening up or the phlenum that holds the heater core is filled with debris loke 30years of pine needles or leaves as far as the water flowing out the overflow don't fill the radiator when it's cold only fill when the motor is up to operating temp __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

12-24-2003, 05:26 PM	#3
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	The radiator problem is something a lot of younger guys don't know about.When the engine and radiator heat up the water/coolant expands overfilling the radiator in effect and causing it to run out the overflow. The later cars used an overflow tank that let the coolant escape to the tank and then it was returned when the engine cooled and created a vacumm.All engines of the non-return line type will use some coolant.They should be filled on ocassion. You can retro fit a coolant overflow and return easily, if you use the tank from a truck with one or install an aftermarket one. New cars are required to have them for EPA, as are race cars to prevent wet spots on the track that cause slick spots. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

12-24-2003, 07:35 PM	#4
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	Yes, like cdowns said, the valve controlling heat flow could not be working (assuming this is a non AC truck). You can look at the flapper valve from inside the cab....it is where the heater control cable goes into the heater box, under the dash in the passenger side footwell. There is a little plastic piece that seals the rectangular hole where the control cable goes in, pop it out and have a look. Make sure the cable is still attached to the lever on the flapper valve, and that it is opening and closing all the way. If that checks out, you proably have a heater core plugged with pine needles or something. You need to remove it....and proably replace it too. A new core is only around $25, and as long as it is out it would be a good idea to replace it. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

12-25-2003, 01:28 PM	#5
nitor Too many projects Join Date: Aug 2002 Location: Morrow, OH Posts: 344	Yellow72 is right. I just had to replace mine. A/C version. Got it at Autozone. It was about $25. __________________ Jim '55 Chevrolet Pickup '56 Chevrolet Belair '04 Chevrolet Astro '95 Chevrolet Blazer

12-25-2003, 01:36 PM	#6
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,608	Same here I just replaced the core in the blazer and it seem's to blow really hot. I also replaced the fan switch that control's the fan speed .. I never knew there was 3 speed's for the fan.. __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

12-25-2003, 05:16 PM	#7
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	lol! of course they are 3 speeds! mine is: 1). off 2). on but nothing comes out the vents 3). on and air is blowing like a hurricane __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650



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