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

67Fleet · 12-26-2005, 06:14 PM

The PO had put a ball valve in-line for the incoming hot water to the heater core. I'm not sure why he would of done this, and it has always been closed. Is it bad to not have water running through there? I'm tempted to open it, but I'm a little nervous about hot water pouring into the cab. There must of been a reason he would have done this..... Any ideas? The original heater controls were broken, and I just got a new heater control for Christmas and installed it, and since the weather has been a little cool (for Florida standards) I wanted to have everything operable. Here's a pic to show where the ball valve is:

Sweet72 · 12-26-2005, 06:20 PM

If the heater controls were inoperative the damper/door that controls airflow across the heater core may have been stuck open, so the PO installed it to keep heat from boiling him out of the cab in summer. A quick fix to keep the heater core cool. The heater core may be corroded since the coolant in it has been stagnant. Pull the hoses off the water pump and intake and flush it out both ways with a water hose.

67Fleet · 12-26-2005, 06:23 PM

So it doesn't harm the engine to have the line shut off there? Doesn't it impede water flow through the intake manifold?

mrein3 · 12-26-2005, 06:39 PM

Factory AC trucks have a vacuum controlled shut off valve in the same spot. Some old school folks put in the manually operated one like you got. Open it up. Next summer if you feel heat bleeding through, close it again.

67Fleet · 12-26-2005, 07:04 PM

Cool, thanks guys!

farside847 · 12-27-2005, 12:25 PM

Or, the core may leak and he put that in for a temp fix.... Look for leaks!

alf1096 · 12-27-2005, 03:42 PM

If it does leak I changed mine yesterday it was very easy but order the new gaskets for the blower moter from lmc and have someone help with the hood

Longhorn Man · 12-27-2005, 10:22 PM

I have always had issues with the hot air getting by the doors in the heater box, and have been looking at doing something like that, but not as bug and ugly though.
While there is a chance that this was put in becouse of a leak, odds are it wasn't. Normally when a leak is found, and the owner doesn't want to repair it, they won't go out and buy a $10 valve to block off an $18 heater core... they'd just run the hose straight from the intake to the water pump, that is free.

**Green Machine** · 12-27-2005, 10:55 PM

Picture isn't very good, but I used a common brass ball valve with the handle cut down attached to the water pump to completly cut the heat in the summer.

Now this is not real pretty either, and I would like to find something that looks better also. I know some a/c cars had a vacuum valve mounted on a tube attached to the intake outlet, but not sure what appication that was. might be a cleaner install.

walker · 12-27-2005, 11:57 PM

If there is only one valve then a leak would still leak with the valve closed, as there is still water and pressure on the core, just no flow.

**kwmech** · 12-28-2005, 12:00 AM

The valve is on the return line back to the engine. Out of the intake and into the pump or radiator.

12-26-2005, 06:14 PM	#1
67Fleet Outlandish Trends - FL Join Date: Jul 2005 Location: Orlando Posts: 1,396	heater core The PO had put a ball valve in-line for the incoming hot water to the heater core. I'm not sure why he would of done this, and it has always been closed. Is it bad to not have water running through there? I'm tempted to open it, but I'm a little nervous about hot water pouring into the cab. There must of been a reason he would have done this..... Any ideas? The original heater controls were broken, and I just got a new heater control for Christmas and installed it, and since the weather has been a little cool (for Florida standards) I wanted to have everything operable. Here's a pic to show where the ball valve is: __________________ -Bret 67 short-fleet sold!

12-26-2005, 06:20 PM	#2
Sweet72 Registered User Join Date: Nov 2003 Location: Alexandria, VA Posts: 1,534	Re: heater core If the heater controls were inoperative the damper/door that controls airflow across the heater core may have been stuck open, so the PO installed it to keep heat from boiling him out of the cab in summer. A quick fix to keep the heater core cool. The heater core may be corroded since the coolant in it has been stagnant. Pull the hoses off the water pump and intake and flush it out both ways with a water hose. __________________ '72 GMC SWB C1500 Custom, frame-off in progress. 383 SBC, 9:1CR, Comp Cams XE262H, Scat internal balanced crank, Eagle SIR 6" rods, Keith Black dish pistons, Dart Iron Eagle 72/180 heads, Weiand Stealth intake, Stewart stage I water pump, Holley 4bbl vac sec, TH350 with B&M Shift Improver Kit. 12 bolt positraction. Last edited by Sweet72; 12-26-2005 at 06:24 PM.

12-26-2005, 06:23 PM	#3
67Fleet Outlandish Trends - FL Join Date: Jul 2005 Location: Orlando Posts: 1,396	Re: heater core So it doesn't harm the engine to have the line shut off there? Doesn't it impede water flow through the intake manifold? __________________ -Bret 67 short-fleet sold!

12-26-2005, 06:39 PM	#4
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	Re: heater core Factory AC trucks have a vacuum controlled shut off valve in the same spot. Some old school folks put in the manually operated one like you got. Open it up. Next summer if you feel heat bleeding through, close it again. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

12-26-2005, 07:04 PM	#5
67Fleet Outlandish Trends - FL Join Date: Jul 2005 Location: Orlando Posts: 1,396	Re: heater core Cool, thanks guys! __________________ -Bret 67 short-fleet sold!

12-27-2005, 12:25 PM	#6
farside847 Registered User Join Date: Feb 2005 Location: Bay Area, California Posts: 995	Re: heater core Or, the core may leak and he put that in for a temp fix.... Look for leaks! __________________ 1971 Chevy C10 Shortbed Stepside, 307v8 3-on-the-tree

12-27-2005, 03:42 PM	#7
alf1096 Registered User Join Date: Aug 2005 Location: Texas Posts: 124	Re: heater core If it does leak I changed mine yesterday it was very easy but order the new gaskets for the blower moter from lmc and have someone help with the hood __________________ 1970 Short Stepside----Process of Restoring 1983 1/2 Silverado

12-27-2005, 10:22 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: heater core I have always had issues with the hot air getting by the doors in the heater box, and have been looking at doing something like that, but not as bug and ugly though. While there is a chance that this was put in becouse of a leak, odds are it wasn't. Normally when a leak is found, and the owner doesn't want to repair it, they won't go out and buy a $10 valve to block off an $18 heater core... they'd just run the hose straight from the intake to the water pump, that is free.

12-27-2005, 10:55 PM	#9
Green Machine Senior Member Join Date: Jul 2004 Location: Estherville, Iowa Posts: 3,371	Re: heater core Picture isn't very good, but I used a common brass ball valve with the handle cut down attached to the water pump to completly cut the heat in the summer. Now this is not real pretty either, and I would like to find something that looks better also. I know some a/c cars had a vacuum valve mounted on a tube attached to the intake outlet, but not sure what appication that was. might be a cleaner install. Attached Images __________________ 1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0

12-27-2005, 11:57 PM	#10
walker Registered User Join Date: Jul 2003 Location: north of Phx AZ about 30 miles Posts: 698	Re: heater core If there is only one valve then a leak would still leak with the valve closed, as there is still water and pressure on the core, just no flow. __________________ Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold

12-28-2005, 12:00 AM	#11
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,505	Re: heater core The valve is on the return line back to the engine. Out of the intake and into the pump or radiator.



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