not much heat

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

allan Johnson

Junior Member
Joined
Jan 31, 2021
Posts
12
Reaction score
11
Location
monnesota
First Name
Allan
Truck Year
1977
Truck Model
c15
Engine Size
350
i got a 1977 gmc 15 non ac fron a guy,he had just put in a new heater core fron ahto zone or one of the discount stores,said it dosent hear like ir did,acualy ter is only minot heat tf is abot 2 degress out side,both heater hoses ans radiar ger hot,of i run down the hyw the heater goes cold,heater door seemsto be workin,o heard some of the new cores are junk or are smaler and need foam packed atound them so the air goes around the core,shoud one of the heater hoses be goin to the radiator instead of both to the motor?this truck never shurs off the heat lt jus directs it thru the core t arond it,seems to me that it shoud be pulling heat ftom the radiator and thats why it gets ice cold of o hit passing gear,gonna take it in as om to old to do it myself
 

RedBeard_83

Full Access Member
Joined
Mar 16, 2020
Posts
554
Reaction score
871
Location
Florida
First Name
Cory
Truck Year
1986
Truck Model
Custom deluxe
Engine Size
Sbc 350
Have you tried bleeding the cooling system. Could be a trapped air bubble preventing coolant from circulating . I had similar issue with mine . once I bled all the air out , my heater worked much better as well as defrost.
 

Babs

Full Access Member
Joined
May 10, 2020
Posts
1,836
Reaction score
8,965
Location
Ottawa Valley
First Name
Paul
Truck Year
1976
Truck Model
Chevrolet CUCV
Engine Size
350
Take your radiator cap off (when cold) Start your truck and leave it running until it reaches its normal operating temperature. It may take between 15 or 20 minutes before your truck generates enough heat to push out the air that has been trapped in your cooling system. You may find that you need to add additional coolant, as air pockets can inflate coolant levels.
 

idahovette

Full Access Member
Joined
Aug 7, 2016
Posts
6,536
Reaction score
14,032
Location
Weiser Idaho
First Name
Perry
Truck Year
1975-1979
Truck Model
K20-K10
Engine Size
350
Both hoses hot, luke warm or cold?....Also when you are done typing, just take a minute and reread what you typed and see if it makes sense to you, that way it will make sense to us....and don't pull the "old" card I'm just a shade behind you!
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,777
Reaction score
9,642
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
New thermostat "technology" has allowed many more "fail-safe" thermostats to be sold and installed.

For example, my thermostat failed - open.
It could have been broke for a year and id never known..
The result is/WAS ;
increased fuel consumption
failed heater
high idle
truck hauls ass

Two Saturdays ago it was -10° overnight in Oklahoma City and I was at work in my truck. The thermometer stuck in the vent read 80° and it was like running the air conditioner!
Worse!
Two 14mm bolts at the thermostat housing after removing the air cleaner?
Five minutes changed at the jobsite. Glue thermostat gaskets to the housing and clean the mating surface on the intake to re-use the gasket. It really probably didnt take 5 minutes. Sure coolant dumped out of the hose.

With a new 195° thermostat, the thermometer now reads 125° inside the vent and that is what you want I reckon.

I suggest to use a 50/50 mix of antifreeze and (distilled) water *for best results in most places.

Since your truck is a '77 you'll need at least one, three inch extension (2 is better) on a ratchet and use 9/16 instead of metric.
9/16 socket and take a scraper and a #2 flathead just in case but try to save the gasket.. I bet I work on mine more than you do fella and it's been very cold.. Be safe out there and dont break a hip workin on your truck, that's not cool.. Aint you got no grandkids or somethin? :crazy:
It's so simple though a trained monkey could do it.
How are the grandkids anyway? Lol..a teenager could handle it easy.
Blindfolded maybe.
With one hand tied behind his back even I bet...
In a snowstorm.
Makin text messages.
While whistling Dixie. ;)
 
Last edited:

Turbo4whl

Supporting Member
Supporting Member
Joined
Oct 30, 2019
Posts
2,868
Reaction score
6,443
Location
Downingtown, PA
First Name
Wayne
Truck Year
1974
Truck Model
Jimmy
Engine Size
350
@Rusty Nail , the only thing you forgot was to drill the bleed hole in the thermostat if it doesn't have a vent.

Good write up. Kids and grand kids are busy playing video games.
 

idahovette

Full Access Member
Joined
Aug 7, 2016
Posts
6,536
Reaction score
14,032
Location
Weiser Idaho
First Name
Perry
Truck Year
1975-1979
Truck Model
K20-K10
Engine Size
350
@Rusty Nail , the only thing you forgot was to drill the bleed hole in the thermostat if it doesn't have a vent.

Good write up. Kids and grand kids are busy playing video games.
For sure about drilling the bleed hole!!! .....On the grandkids, any of them will come running if I ever shout out to them, very lucky that way!!!!
 

CRM

Full Access Member
Joined
Jun 6, 2016
Posts
1,188
Reaction score
2,775
Location
Pasco, Washington
First Name
Casey
Truck Year
1985
Truck Model
K2500
Engine Size
350 CI
I'm not trying to be a jerk. If you can't operate something as simple as a keyboard then why should you being driving a 2,000 lb truck out in public and putting lives at risk? How hard is it to go back over your spelling and correct things before posting?
 

Octane

Full Access Member
Joined
Dec 31, 2019
Posts
2,004
Reaction score
3,571
Location
Atlanta
First Name
Eddie
Truck Year
1977
Truck Model
K10
Engine Size
350
It was certainly not my intention.
I thought he was using the mic to write the post.My bro does that and it'll print some strange stuff.And he wont proofread it either.I never know what he means lots of times and its so bad.
 

Grit dog

Full Access Member
Joined
May 18, 2020
Posts
5,941
Reaction score
9,817
Location
Washington
First Name
Todd
Truck Year
1986
Truck Model
K20
Engine Size
454
I'm not trying to be a jerk. If you can't operate something as simple as a keyboard then why should you being driving a 2,000 lb truck out in public and putting lives at risk? How hard is it to go back over your spelling and correct things before posting?

Wow!
Edit: Don’t throw stones from your glass house.
 
Last edited:

Grit dog

Full Access Member
Joined
May 18, 2020
Posts
5,941
Reaction score
9,817
Location
Washington
First Name
Todd
Truck Year
1986
Truck Model
K20
Engine Size
454
Mr. Johnson, good suggestions so far.
Ensure the cooling system is actually full and bled and pushing hot water through the heater core. I don't remember where each hose comes from but believe feed is off the water pump and return to the intake?
If that's good verify if the blend door isn't stuck and blocking airflow through the heater core.
 
Top