Help with no heat please - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cochino12 · 02-24-2016, 12:05 PM

So I removed my 4.3 for a 350 and now I have no heat in the cab. Upper radiator hose gets hot, truck warms up to normal temperature, lower radiator hose and both hoses to heater core are cold (one to intake other to radiator).

Any ideas? Thanks

Ski-me · 02-24-2016, 01:06 PM

plugged hose? Did you run engine from cold with radiator cap off to try and get the air out of system? Thermostat?

crazeetxn · 02-24-2016, 03:25 PM

So it will get to normal temp but not overheat? And still the hoses are cold? Was hoping it would be a thermostat issue. Easier than a heat core. Stick a water hose up to the heater core hoses and see if it flows or if it's clogged.

Ski-me · 02-24-2016, 04:25 PM

when I changed my water pump, I drove it and started overheating. I pulled over and felt my upper radiator hose...cold.

Let the truck cool down and then pulled cap off of radiator. Ran it, topped it off and then no more issues. So my problem was just burping the system, so to speak.

truckin 79 · 02-24-2016, 07:32 PM

yeah you might just have air on the system. Do you have a overflow reservoir hooked up to radiator?

Prerunner1982 · 02-25-2016, 10:13 AM

If the old engine was not out for very long and the heater worked with the old engine I would be surprised if the heater core is plugged. If the engine was out and the hoses disconnected for a bit I suppose something could have got in there and clogged it up.

Try bleeding the coolant first and go from there, hopefully it's that easy.

cochino12 · 02-25-2016, 04:13 PM

thanks for the input guys. I think the problem is a clogged heater core, tried flushing it out and a whole lot of nasty sludge is coming out.

Do I need to drain the rest of the cooling system now? Coolant looks ok

geezer#99 · 02-25-2016, 04:17 PM

Could be heater hoses hooked up wrong.
Intake to bottom on core.
Top of core to rad.

wilkin250r · 02-25-2016, 06:58 PM

I have seen a rare instance when the heater core was partially plugged (I think the previous owner used a radiator stop-leak too many times), and only one or two coils in the heater core were open. As a result, you could indeed get a water flow through the heater core, but no significant transfer of heat.

When we changed the heater core, it cooked him out of the cab. I took the old core and cut it open to verify what the problem was.

02-24-2016, 12:05 PM	#1
cochino12 It followed me home? Join Date: Mar 2003 Location: Yup Posts: 5,751	Help with no heat please So I removed my 4.3 for a 350 and now I have no heat in the cab. Upper radiator hose gets hot, truck warms up to normal temperature, lower radiator hose and both hoses to heater core are cold (one to intake other to radiator). Any ideas? Thanks __________________ Adam That's why they call it a shortcut Kyle, if it was easy it would just be the way. 86 c-10 SWB 85 CCSB 90 GMC K30 Crew SRW 1985 C30 Dually

02-24-2016, 01:06 PM	#2
Ski-me Registered User Join Date: May 2012 Location: Colo Springs, CO Posts: 870	Re: Help with no heat please plugged hose? Did you run engine from cold with radiator cap off to try and get the air out of system? Thermostat? __________________ - Jeff 89' K5 Blazer, 2.5" lift, 35" tires 04' GMC Yukon XL, 3/4 ton, 8.1L

02-24-2016, 03:25 PM	#3
crazeetxn Registered User Join Date: Aug 2011 Location: Winnsboro TX Posts: 234	Re: Help with no heat please So it will get to normal temp but not overheat? And still the hoses are cold? Was hoping it would be a thermostat issue. Easier than a heat core. Stick a water hose up to the heater core hoses and see if it flows or if it's clogged. __________________ 1st - '68 long bed 2nd - '81 SWB Now - '86 SWB, Edelbrock 1406/stock 350/700r4

02-24-2016, 04:25 PM	#4
Ski-me Registered User Join Date: May 2012 Location: Colo Springs, CO Posts: 870	Re: Help with no heat please when I changed my water pump, I drove it and started overheating. I pulled over and felt my upper radiator hose...cold. Let the truck cool down and then pulled cap off of radiator. Ran it, topped it off and then no more issues. So my problem was just burping the system, so to speak. __________________ - Jeff 89' K5 Blazer, 2.5" lift, 35" tires 04' GMC Yukon XL, 3/4 ton, 8.1L

02-24-2016, 07:32 PM	#5
truckin 79 Registered User Join Date: Jun 2014 Location: CO Posts: 737	Re: Help with no heat please yeah you might just have air on the system. Do you have a overflow reservoir hooked up to radiator? __________________ 79 Chevy 2wd BIG10 350 TH400

02-25-2016, 10:13 AM	#6
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,906	Re: Help with no heat please If the old engine was not out for very long and the heater worked with the old engine I would be surprised if the heater core is plugged. If the engine was out and the hoses disconnected for a bit I suppose something could have got in there and clogged it up. Try bleeding the coolant first and go from there, hopefully it's that easy. __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

02-25-2016, 04:13 PM	#7
cochino12 It followed me home? Join Date: Mar 2003 Location: Yup Posts: 5,751	Re: Help with no heat please thanks for the input guys. I think the problem is a clogged heater core, tried flushing it out and a whole lot of nasty sludge is coming out. Do I need to drain the rest of the cooling system now? Coolant looks ok __________________ Adam That's why they call it a shortcut Kyle, if it was easy it would just be the way. 86 c-10 SWB 85 CCSB 90 GMC K30 Crew SRW 1985 C30 Dually

02-25-2016, 04:17 PM	#8
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,542	Re: Help with no heat please Could be heater hoses hooked up wrong. Intake to bottom on core. Top of core to rad.

02-25-2016, 06:58 PM	#9
wilkin250r Registered User Join Date: Sep 2010 Location: Lake Tahoe, Nevada Posts: 755	Re: Help with no heat please I have seen a rare instance when the heater core was partially plugged (I think the previous owner used a radiator stop-leak too many times), and only one or two coils in the heater core were open. As a result, you could indeed get a water flow through the heater core, but no significant transfer of heat. When we changed the heater core, it cooked him out of the cab. I took the old core and cut it open to verify what the problem was. __________________ I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!!



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