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Topic: Heater Core Bypass

in Forum: C3 Cooling and Heating Systems


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Heater Core Bypass (1/23)
 6/6/09 11:58pm
manget1Lifetime Member
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Indianapolis, IN - USA

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Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
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Certainly, the topic of heat inside a C3 has been discussed a number of times.  I know some folks have discussed the bypassing of the heater core, but I glanced around and did not find one specific post to discuss the process.  So, how do I go about doing this in the best way to try to keep the heat out of the passenger area?
 
Thanks in advance!


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Heater Core Bypass (2/23)
 6/7/09 2:21am
tb2k82ceLifetime Member
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Lemon Grove, CA - USA

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1982 C3 Collectors Edition 44000 miles, sat in the sun most of its life, My wife purchased it for me for Father's Day in 2007 from her girlfriend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.


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This is the Link ..  I did it when I replaced my heater core which was when I replaced my dash.  I can provide pictures if you need or want them.

If the link does not work it is on the top of the forth page on the "C3 Cooling and Heating Systems" forum.


(inserted clickable link)

Adams' Apple2009-06-07 12:15:00
Heater Core Bypass (3/23)
 6/7/09 10:09am
KDADDY79
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Dutchess County, NY - USA

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Hey Marshall,
I went ahead and did that last year. All it took was new heater hoses, a five eighths & a three quarter shut off valve plus a leap of faith, which I got here.
There is some debate over the necessity of connecting the water pump hose to the 2nd. heater hose which enters the intake manifold. I didn't do that but plan on it when I can.
I'm not much of a mechanic but I was able to get it done.
Kevin
Heater Core Bypass (4/23)
 6/7/09 1:45pm
aceintheholeLifetime Member
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Manteca, CA - USA

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1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed


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The inline positive shutoff valves work great and it's not complicated once you drain off the coolant. Just cut in to each hose and install a valve, clamp them back on and your all set. Leave open for winter and off during the summer. I did mine down low on the hoses before they enter the fire wall so they were less noticable. 

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Heater Core Bypass (5/23)
 6/7/09 4:47pm
manget1Lifetime Member
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Indianapolis, IN - USA

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Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
Posts: 2418

You know, as common as this problem is, I'm surprised Mid America and the other vendors don't have a "package" solution.  Years ago, I simply did a bypass of my heater core in my 76 Grand Prix by taking the two heater hoses and running them from one to the other with a metal fitting.  Anyone done anything like that?
 
Thanks everyone.  I'll take a look at the links
manget12009-06-07 13:55:23

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Heater Core Bypass (6/23)
 6/8/09 8:05am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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I actually prefer to tie the two hoses together. If what you're trying to do is remove heater core heat from teh passenger compartment, it's the only way to completely eliminate heat transfer. Even with the shut-off valves in both lines, heat will still transfer from the engine-side hoses thru the valves...it's called convection heat. Just because water(coolant) is not circulating thru the core doesn't mean the heat is gone...just diminished.
Do the shut-off valves help? You betcha. But disconnecting the hoses entirely eliminates the heat transfer completely.
It's six one way and half a dozen the other...


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Heater Core Bypass (7/23)
 6/9/09 5:21am
manget1Lifetime Member
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Indianapolis, IN - USA

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Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


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That's exactly what I'm hoping to do Joel!  Anyone know of a part out there designed for that?  Back in the day, I just looked around the shop, but that was a long time ago...



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Heater Core Bypass (8/23)
 6/9/09 7:58am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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One problem will be that the two hoses are different sizes...on is 5/8" id, and the other is 3/4" id. I've used 5/8" pipe, and the 3/4" hose will clamp down it it. It's a bit harder to get the 5/8" hose to stretch to fit a 3/4" pipe...Angry
Your local hardware store will have the part you need...just don't tell them it's for a Corvette...they'll jack the price up...


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Heater Core Bypass (9/23)
 6/9/09 11:40am
dsireme
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South Milwaukee, WI - USA

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1978 L82 4spd coupe/3.73:1 Differential Ratio /Black with Yellow Pinstripes and Black Interior/AC/Tilt/AM FM Stereo/Pretty Much Stock


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One - Thank you Marshall, I actually logged on to ask this question today. Ted and I took the Vette to Madison to see Jeff Dunham (awesome show, front row seats)  and on the way home he said how can you drive in this car, it is so uncomfortable and I said it isn't cushioned that bad and he said "MY ASS IS HOT!" My car is definitely hot and not the way I want it to be. My feet burn have the time. '
 
Two - you guys are scaring me. Can I actually do this myself? We are talking about me, the computer geek here, not a car person.
 
And Joel, what is this tying hoses together, is the like having your tubes tied??? Confused I am so confused. All I know is even when I use my AC the car is still hot at the feet.
Heater Core Bypass (10/23)
 6/9/09 11:47am
dsireme
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South Milwaukee, WI - USA

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Heater Core Bypass (11/23)
 6/9/09 12:37pm
aceintheholeLifetime Member
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Manteca, CA - USA

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[QUOTE=dsireme]Is this the valve everyone is talking about???
 
 
Also I had found this:
 
http://temp.corvetteforum.net/c3/joeveto/Hot_Water_Shut-Off.shtml
[/QUOTE]



 Not sure how well the plastic one works. I used the metal style, but you don't have to mess with the copper tubing. You could just buy the screw in hose barbs, and use a little teflon tape to seal the threads.

(fixed quote box)
Adams' Apple2009-06-09 09:56:26

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Heater Core Bypass (12/23)
 6/9/09 12:51pm
dsireme
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South Milwaukee, WI - USA

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1978 L82 4spd coupe/3.73:1 Differential Ratio /Black with Yellow Pinstripes and Black Interior/AC/Tilt/AM FM Stereo/Pretty Much Stock


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[QUOTE=aceinthehole][QUOTE=dsireme]Is this the valve everyone is talking about???
 
 
 
Also I had found this:
 
 
 
 Not sure how well the plastic one works. I used the metal style, but you don't have to mess with the copper tubing. You could just buy the screw in hose barbs, and use a little teflon tape to seal the threads. [/QUOTE]
 
Screw in what?(no comment some of you) I have no clue what that is.

(fixed quote box)
Adams' Apple2009-06-09 09:58:32
Heater Core Bypass (13/23)
 6/9/09 1:03pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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[QUOTE=dsireme]And Joel, what is this tying hoses together, is the like having your tubes tied??? Confused [/QUOTE]

Well...I wouldn't know...my tubes have never been tied...Clown(that I'm aware of...)

What I am referring to is removing the hoses from the heater core, and installing a short piece of metal tubing to connect the two hoses(from the engine) together. It's like taking two hoses to make one...does that help?
Adams' Apple2009-06-09 10:04:00

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Heater Core Bypass (14/23)
 6/9/09 1:18pm
dsireme
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South Milwaukee, WI - USA

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1978 L82 4spd coupe/3.73:1 Differential Ratio /Black with Yellow Pinstripes and Black Interior/AC/Tilt/AM FM Stereo/Pretty Much Stock


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[QUOTE=Adams' Apple] [QUOTE=dsireme]And Joel, what is this tying hoses together, is the like having your tubes tied??? Confused [/QUOTE]

Well...I wouldn't know...my tubes have never been tied...Clown(that I'm aware of...)

What I am referring to is removing the hoses from the heater core, and installing a short piece of metal tubing to connect the two hoses(from the engine) together. It's like taking two hoses to make one...does that help?
[/QUOTE]
 
Ok, so pretty much just by-passing the heater core all together... which is a good idea except in wisconsin it maybe hot in the day time but sometimes still 45 in the morning.
 
Can you some how show me what hoses I would do this with? I mean in the hot summer months it would be great.
Heater Core Bypass (15/23)
 6/9/09 4:01pm
aceintheholeLifetime Member
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Manteca, CA - USA

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1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed


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[QUOTE=dsireme] Screw in what?(no comment some of you) I have no clue what that is.[/QUOTE]
 
Just to clarify, the metal plumbing style vavles come with different ends. The type shown in the pics were a compression type that use a brass nut and ferrule to tighten and seal around a smooth pipe. I prefer the threaded style that allows you to screw fittings in to both ends. The fittings, also available at the hardware store, are of brass, about 2" long. Threaded on one end and with hose barbs on the other, so that you can slip a hose on to it and clamp it down. I hope that makes sense. I'm just not good with pics yet.


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Heater Core Bypass (16/23)
 6/9/09 6:37pm
manget1Lifetime Member
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Indianapolis, IN - USA

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Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible


Joined: 9/3/2006
Posts: 2418

The piece I used 20 years ago on my Grand Prix was a U-shaped metal tube.  I'll check out the plumbing area of my local Home Depot and see if I can find anything with two different sizes on either end.
 
TJ, not sure how you feel riding in your car, but as the driver, I rarely experience issues with heat.  It's always the passenger with issues.


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Heater Core Bypass (17/23)
 6/9/09 8:46pm
crossfire1982
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Cramerton, NC - USA

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black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion


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If you are going to install only one valve you would install a valve in THIS hose where Im pointing.   If you are going to install two valves, the second one would go on the hose which exits the heater core and goes to the water pump HERE.  If you prefer the valves not to show, they can be installed under the car but still in reach without lifting the car LIKE THIS.  These valves are under the car near the heater core inlets where the hoses turn upward to connect to the core.  The valves you see are the NAPA valves.
Heater Core Bypass (18/23)
 6/23/09 10:11am
mysticstriper
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Saraland, AL - USA

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1980 L82


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My heater core has been bypassed by  hose, the bad part is I don't see where the hoses should hook to the heater core. I LIKE a heater in the winter even here in the south.So, I'm having vacuum line problems with my A/C-the A/C  blows nice and cold below the dash but the vacuum lines that operate the ducts are not there so I'll be tracing and replacing them but at the same time I would really like to know where my heater core is! On most GMs it's in the fiberglass box that is by the A/C dryer, but I see no tubes sticking out there...help anyone?
Heater Core Bypass (19/23)
 6/23/09 10:44am
rraider1
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Woodland, WA - USA

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1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion


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How come mo one makes sure the valve installed into the car is working. The valve installed is operated by vacum from a vacum switch behind the passenger dash panel and is acuated by the temp selector being moved to the off position. (1977) not shure the different year changes but should be similiar. If operation is correct the water is shutoff. then as to Joels point you would want to add the valve on the return side to stop the convection off heat from that hose. which if we were to install another vacum valve on this hose and tee it off, it should block all heat and work automaticly no mechanical valvesneeded?
Heater Core Bypass (20/23)
 6/23/09 10:57am
DaveMLifetime Member
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Flanders, NJ - USA

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[QUOTE=mysticstriper]My heater core has been bypassed by  hose, the bad part is I don't see where the hoses should hook to the heater core. I LIKE a heater in the winter even here in the south.So, I'm having vacuum line problems with my A/C-the A/C  blows nice and cold below the dash but the vacuum lines that operate the ducts are not there so I'll be tracing and replacing them but at the same time I would really like to know where my heater core is! On most GMs it's in the fiberglass box that is by the A/C dryer, but I see no tubes sticking out there...help anyone?[/QUOTE]
The tubes are on the bottom, need to get under the car to get to them.

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Heater Core Bypass (21/23)
 6/23/09 12:49pm
anips
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sonoma, CA - USA

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72 LT-1 AC coupe,69 l-36 coupe


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I installed two valves and it helped alot but I still get some warm air in the corkpit with the heater off, cause with the ign switch on the fan motor still runs with the fan switch off, has something to do with the Astro ventalation set up ,so now what I do during the summer is close the valves and disconect the fan ground lead so that the fan doesn't run, I don't run my AC cause it throws compressor oil, even when I replaced the seal, long ago I read somewhere here that you could disconnect a brown wirer I believe at the AC blower motor cut out relay or blower motor risistor I can't remember or find it again, but it kills the  the low speed on the blower motor but it still allows med and high to work, I'd post photos of my valve set up but don't have a clue on how to do itConfused anips2009-06-23 18:50:19
Heater Core Bypass (22/23)
 6/23/09 1:44pm
rraider1
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Woodland, WA - USA

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Just for info sake I went to napa this morning to get my brake rotors (another project) the parts guy found me avacum of control vale that is for 3/4 in hose. so I had him order it for me and I will install and see how it works.
Heater Core Bypass (23/23)
 6/23/09 2:14pm
my7t1Lifetime Member
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Dorr, MI - USA

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I totally agree with Joel. If you want to shut off heat, ya might as well do it completly with bypass connector. With my 71 its easy, as the heater hoses are right behind the side grill. You can get hose reducers, 5/8" to 3/4" at any auto store. I know because I order them 2 doz. at a time. As far as vacuum control valves,  iffin they worked you wouldn't have this problem in the first place. With manual valves your only gonna shut off part of the heat, not all of it as previously mentioned.
 
My cooling system professional .02.
 
 


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