Help! Heater Box overheating? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

wldcat10 · 10-12-2010, 06:58 PM

Hows it going everyone? I need help with something. I've noticed that after I park my truck I hear a bubbling sound like boiling water coming from the passenger side behind the dash. I'm thinking it's my heater box, but I dont know what I need to do to fix it? Any help would be appreciated, thanks!

**John Fabris** · 10-12-2010, 07:03 PM

that would mean you have a leak in your cooling system. Check your heater hoses (in the engine compartment), and if you don't see a leak (look for white build up, calcium) then its possible that your heater core is bad and needs to be replaced.

71 super · 10-12-2010, 11:00 PM

You have a leak as john said, core or hose. Not to bad to fix, but will have to drop your inner fender if a non air truck.

ChevLoRay · 10-12-2010, 11:03 PM

Find a cooling system pressure tester and pressurize your cooling system. If you can't borrow one, then a service station or garage should have one and can pressurize it for you. When I was at Sears Auto Center, we also had one so Sears, or a Firestone or Goodyear store are other possibilities.

BluTrukker · 10-13-2010, 07:40 AM

I had a 91 chevy that had the same sound. Not constant, but occasionally. When I changed the engine, apparently I got an air bubble in the heater core. I tried everything to get it out, but nothing worked. I drove it like that for 3 years until I sold it.

swamp rat · 10-13-2010, 11:58 AM

I agree it sounds like you will have to open the heater box up and find out if your core is leaking, doing a pressure test is a good place to start, if there is a leak it won't hold pressure, then you would have to pinpoint the leak

Also make sure you have the water hose from your intake manafold (outlet) port routed to your lower heater (inlet) port? the core is suppost to fill from the bottom to the top to purge the air out of the heater core the top shopuld go ether to your radiator if you have the connection, or back to the port on the waterpump..

Andy4639 · 10-13-2010, 12:09 PM

Look in the passenger side floor board and see if there is any sign's of leakage in the floor under the carpet or floor matting.
Ok, then if not look out in the engine bay under the passenger side and see if you see any signs of it. If you can't find anything wet. Take the bottom and top heater hoses off and put your water hose on the bottom one and turn it on and see if it's blocked up. If not then it's a hose leak somewhere.

raycow · 10-13-2010, 01:26 PM

Definitely check for leaks first. Now after you don't find any......
When you shut down an engine, water in contact with hot spots can start to boil locally, since there is no longer any circulation to carry away the heat. This is not harmful in itself. However, the vapor bubbles created by the boiling are lighter than water and want to migrate to high points in the cooling system, which just happen to include the heater core.

Ray

10-12-2010, 06:58 PM	#1
wldcat10 Registered User Join Date: Apr 2010 Location: Tucson, Arizona Posts: 157	Help! Heater Box overheating? Hows it going everyone? I need help with something. I've noticed that after I park my truck I hear a bubbling sound like boiling water coming from the passenger side behind the dash. I'm thinking it's my heater box, but I dont know what I need to do to fix it? Any help would be appreciated, thanks! __________________ 1970 CST/10 LWB 350 1984 Blazer

10-12-2010, 07:03 PM	#2
John Fabris TOTY 2006 Join Date: Dec 1999 Location: Magalia CA USA Posts: 2,270	Re: Help! Heater Box overheating? that would mean you have a leak in your cooling system. Check your heater hoses (in the engine compartment), and if you don't see a leak (look for white build up, calcium) then its possible that your heater core is bad and needs to be replaced. __________________ John Fabris 67 C10 SWB

10-12-2010, 11:00 PM	#3
71 super Registered User Join Date: Sep 2005 Location: Canton North carolina Posts: 3,079	Re: Help! Heater Box overheating? You have a leak as john said, core or hose. Not to bad to fix, but will have to drop your inner fender if a non air truck. __________________ 67 blue step side- bb 68 gold and white swb cst anniversary 68 custom swb hot rod Ls swap 69 swb cst 6 cylinder/ overdrive 69 black/black cst bb swb 70 orange and white cst Canada built truck swb bb 71 black and white super swb bb 71 red and white super swb 72 green and white super swb 4x4 62 nova wagon 400 series Ls swapped 68 Camaro 327/4 speed- 1 owner, original paint 66 Volkswagen bettle 69 auto stick Volkswagen Beetle

10-12-2010, 11:03 PM	#4
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: Help! Heater Box overheating? Find a cooling system pressure tester and pressurize your cooling system. If you can't borrow one, then a service station or garage should have one and can pressurize it for you. When I was at Sears Auto Center, we also had one so Sears, or a Firestone or Goodyear store are other possibilities. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

10-13-2010, 07:40 AM	#5
BluTrukker BOHICA Join Date: Mar 2008 Location: Stewartville, MN Posts: 440	Re: Help! Heater Box overheating? I had a 91 chevy that had the same sound. Not constant, but occasionally. When I changed the engine, apparently I got an air bubble in the heater core. I tried everything to get it out, but nothing worked. I drove it like that for 3 years until I sold it. __________________ Trying to save someone from their own stupidity is like teaching a pig to dance. It is a waste of your time, and it annoys the pig!

10-13-2010, 11:58 AM	#6
swamp rat Registered User Join Date: Oct 2007 Location: Spanaway Posts: 8,451	Re: Help! Heater Box overheating? I agree it sounds like you will have to open the heater box up and find out if your core is leaking, doing a pressure test is a good place to start, if there is a leak it won't hold pressure, then you would have to pinpoint the leak Also make sure you have the water hose from your intake manafold (outlet) port routed to your lower heater (inlet) port? the core is suppost to fill from the bottom to the top to purge the air out of the heater core the top shopuld go ether to your radiator if you have the connection, or back to the port on the waterpump.. __________________ Mike. Swamp Rat build thread : http://67-72chevytrucks.com/vboard/s...d.php?t=595019 72 3/4T 4X4 4" BDS Lift 33" BFG's

10-13-2010, 12:09 PM	#7
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Help! Heater Box overheating? Look in the passenger side floor board and see if there is any sign's of leakage in the floor under the carpet or floor matting. Ok, then if not look out in the engine bay under the passenger side and see if you see any signs of it. If you can't find anything wet. Take the bottom and top heater hoses off and put your water hose on the bottom one and turn it on and see if it's blocked up. If not then it's a hose leak somewhere. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

10-13-2010, 01:26 PM	#8
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: Help! Heater Box overheating? Definitely check for leaks first. Now after you don't find any...... When you shut down an engine, water in contact with hot spots can start to boil locally, since there is no longer any circulation to carry away the heat. This is not harmful in itself. However, the vapor bubbles created by the boiling are lighter than water and want to migrate to high points in the cooling system, which just happen to include the heater core. Ray



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