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Topic: Heater core or ??else

in Forum: C3 Cooling and Heating Systems


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Heater core or ??else (1/16)
 3/10/12 9:26am
myhigh76
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Traverse City, MI - USA

Vette(s):
1976 coupe 35K miles


Joined: 12/15/2011
Posts: 6

Please help...so when I turn on my heater a mist of fog begins to cover the windshield. The defroster will not eliminate the mist.  The air condition works great ( no mist/fog) and there is no evidence of water on the passenger side floor. This a 1976 Corvette . This is my first time on the forum and the stuff you guys know is VERY impressive. I hope you can/will help me 'cause my wife does like the heat on cool Spring and Fall morning drives. Anything???


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Re: Heater core or ??else (2/16)
 3/10/12 9:39am
lukesvetteLifetime Member
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HOWELL, NJ - USA

Vette(s):
1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.


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Without a doubt a leaky heater core. I'll bet that your passenger side carpeting may be dampened with antifreeze also.

Somewhat of an involved job to replace it. In the near term, you could re-route or eliminate the heater hoses to the heater core and let that puppy dry out. 

We've had a couple of cars where this happened and we just plugged the manifold and water pump outlets until we were ready to get into the dash and AC doghouse.

Good luck!

Paul 
Re: Heater core or ??else (3/16)
 3/10/12 10:05am
myhigh76
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Traverse City, MI - USA

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1976 coupe 35K miles


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Thanks for the reply...Zero water on passenger side, that's why I can't explain the problem. Pulled up the carpet...no moisture.  Would there be evidence of leakage in another area??  Again thanks for you input.


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Re: Heater core or ??else (4/16)
 3/11/12 12:21am
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top


Joined: 5/18/2010
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Look well try and see if the cool ac air cleans it off...leave the heat off and turn on the ac only..meaning the evaporator is not getting used by the VIR...the blend door might not be working letting the evaporator do its job...there may be a vacuum leak somewhere so its not working to remove the water in the air...if you're certain the ac is working and fully charged it should remove the water in the air when in use..I know mine gets fogged fast if I have the top up and don't use the ac to clear it off and it does fog up as soon as I turn on any air on the windshield...so bad that I can't see out of the car..

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Re: Heater core or ??else (5/16)
 3/11/12 12:27am
yostusota
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York, PA - USA

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1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top


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Ok..so I read your post again and it says ac on no mist...so that does point to the blend door not working right...give that a look and see what you find.

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Re: Heater core or ??else (6/16)
 3/11/12 7:40am
lukesvetteLifetime Member
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HOWELL, NJ - USA

Vette(s):
1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.


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Posts: 6812

With nothing on the floor, I think Rich is on the right track - assuming then no antifreeze odor at all in the passenger compartment.
Re: Heater core or ??else (7/16)
 3/11/12 8:51pm
2 cruznLifetime Member
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Poquoson, VA - USA

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73 Conv, Blue-Green/White Top - 454, M21 - Dark Saddle Leather, Power Windows, A/C, Tilt/Tele, AM/FM St. (orig. and sounds like it too).#2 -- 2007 Coupe,3 LT package, Z51 option, Victory Red, Ebony Int. Clear Top.


Joined: 11/20/2004
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first of all.... Are you losing anti freeze? Do a presure check on the heater core thru the supply and return hoses

|UPDATED|3/11/2012 5:51:41 PM (AZT)|/UPDATED|


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Re: Heater core or ??else (8/16)
 3/11/12 1:16pm
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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Couple o comments...
With the A/C running, you shouldn't be getting any airflow to the top, anyway, so misting wouldn't be an issue. Also, with the Defrost ON, the A/C compressor should be running, which should eliminate the fogging...as it's supposed to do.
High humidity can cause this in certain parts of the country, and could be considered normal. There could also be some standing water in the cowl/vent area that can cause it, if the cowl drains are stopped up. However...using the Defrost should eliminate the fogging almost immediately. I kinda hafta agree wid Rich, in that the diverter doors may not be moving as they should be, whether due to a vacuum problem, a bent/warped door, or a linkage issue...


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Re: Heater core or ??else (9/16)
 3/12/12 9:25am
my7t1Lifetime Member
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Dorr, MI - USA

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71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp


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IMHO. I would still lean towards the heater core. Often when they start to leak its ever so slight in the middle of the core. Hence not enough to spill out on the carpet. Plus some of the coolant will fall into the evap drain tray and run out the drain hole on the firewall side. The problem your describing is exactly the way my 71 started out leaking until she finally let go. The mist started on the corner of the pass. window. If mist is forming all the time this is what I would expect. If only when its humid out I would agree with possible AC issue. What I would do is bypass the heater temporally and run the heater for a few days to dry out the core. Then run the air for a while see what it does. If the mist goes away with just the heater on I would lean towards the heater core.
Oh and to mention I have replaced hundreds of heater cores on various models that did the same thing. Not always bad enough leak to make a foot washer on the pass. side. But like mentioned, its kind of a pretty intense job to replace the core, so I would be 100% before tearing into it.

My .02, "T"



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Re: Heater core or ??else (10/16)
 3/12/12 11:46am
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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Heater cores can indeed seep enough to cause this, and not show up as leakage on the floor, for sure. Ya wanna be sure that's what it is before ripping the dash apart. I agree with bypassing the core to find out, and, as Terry points out, you'll need to run it a while before all of the coolant dries up off of the core, so it's not just a by-pass and check deal...if it is the core, it will still fog up for a while, until the coolant dries up...Wink
This is when having a bore/video scope is very useful. You can snake a borescope up in there, and have a looky-loo, to see if the core is moist/wet.


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Re: Heater core or ??else (11/16)
 3/12/12 2:07pm
dskopp
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Oak Creek, WI - USA

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Adams' Apple said: Heater cores can indeed seep enough to cause this, and not show up as leakage on the floor, for sure. Ya wanna be sure that's what it is before ripping the dash apart. I agree with bypassing the core to find out, and, as Terry points out, you'll need to run it a while before all of the coolant dries up off of the core, so it's not just a by-pass and check deal...if it is the core, it will still fog up for a while, until the coolant dries up...Wink
This is when having a bore/video scope is very useful. You can snake a borescope up in there, and have a looky-loo, to see if the core is moist/wet.



Joel:  is that like a broncoscopy??  or a colonoscopy????  lol
DanLOLTongue


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Re: Heater core or ??else (12/16)
 3/12/12 2:11pm
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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LOL
It's a coreoscopy!!


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Re: Heater core or ??else (13/16)
 3/12/12 9:00pm
myhigh76
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Traverse City, MI - USA

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1976 coupe 35K miles


Joined: 12/15/2011
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Gentlemen...Thank you all for the input on the heater core. I have been out of town for the past few days and just now sat down to go through my email. I WILL begin to trouble shoot the problem using your ideas. Hopefully I can start this week. Please know that I am grateful for the response to this problem. I will keep you posted as we progress . I may have to get clarification  on some of the stuff you have suggested.  Thanks again.

Larry


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Re: Heater core or ??else (14/16)
 7/9/12 1:11pm
68vet427
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macedon, NY - USA

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Hi Guys,

along this subject, if you do bypass the heater core , will that affect the running temp of the engine?
in other words, will it cause it to overheat ?
Thanks
Joe
Re: Heater core or ??else (15/16)
 7/9/12 1:15pm
68vet427
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macedon, NY - USA

Vette(s):
68 COUPE 454 HAS MOTION HOOD SCOOP, REVERSED GILLS ZL-1 FENDER FLARES AND MOTION REAR SPOILER, LEMAN'S GAS CAP, BUCKET HEADLIGHTS. CAN-AM FRONT RACING SPOILER. CHROME HOOKER HEADERS AND SIDE PIPES! 4 SPEED M20, LOOKS FAST STANDING STILL !!


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Ok just saw a different post that may have answered my question excecpt about the overheating.
Re: Heater core or ??else (16/16)
 7/9/12 8:58pm
RedwingvetteLifetime Member
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Waterford, MI - USA

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1973 Red coupe


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No way will by-passing the heater core cause overheating unless you have some other issues.
 
If you need to checkout/change your heater core then this information may help:


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