Heater Core Removal
Thread Starter
Advanced
Joined: Jun 2013
Posts: 87
Likes: 12
Heater Core Removal
I'm pretty sure my heater core has a leak. I drove the car for the first time this year, a few days ago. After the engine was at 140 degrees, I backed out and onto the road, and a "mist" came out of the defroster grill and fogged up the entire windshield. The heater was not turned on. I later searched but could not find any apparent leak of fluid inside the car. My car is an early 1968 with factory air. My question is whether the heater core can be removed from inside the car?
Burning Brakes
Joined: Feb 2008
Posts: 826
Likes: 119
From: Lincoln NE Riding and Driving Corvettes since 1967.
The heater core has to be removed from inside the cabin. The core is attached to the inner case not the outer case. Lots more vacuum hoses to deal with due to factory ac that operate vacuum pods. This is definitely not a fun job. I've done a bunch of c3 heater cores including my November 67 built 68 convertible. You will want to recore your original Harrison heater core as there are no reproductions that are anywhere close to fitting correctly.
Give me a shout if you need assistance
Bigredbrad
Give me a shout if you need assistance
Bigredbrad
Melting Slicks
Joined: Apr 2021
Posts: 2,672
Likes: 2,124
From: Minnesota
Do you plan on driving your car during cold weather? If not you might just want to cap off the ports on the engine and leave it be. Like what was said above though, it has to be done from inside the car.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,052
Likes: 4,194
From: US-PNW
Yeah with A/C, it's gotta come out from the passenger foot well. Not a horrible job, lots of ducting and vacuum hoses, and most of the work is done from the inside, but there is a nut that must be removed from the engine firewall. Take a lot of disassembly pics as you go.
Race Director
Joined: Jan 2007
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Likes: 695
From: Danville Illinois
2025 Corvette of the Year Finalist - Modified
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On our 75 with AC it was all done from inside the cabin, one nut under the hood tho.
Remove the passenger seat for room to work on it, wife helped, still a fun project tho.
Pressure test the new unit at a radiator repair place, make sure the pipe bends are the same.
Remove the passenger seat for room to work on it, wife helped, still a fun project tho.
Pressure test the new unit at a radiator repair place, make sure the pipe bends are the same.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,573
Likes: 7,017
From: New Or-leens Loo-z-anna
Questions: Did you get a wiff of the mist? Did it smell like warm antifreeze/coolant. You really shouldn't remove the heater core until you determine if the mist was coolant or A/C mist...two different smells and the A/C mist would be very oily on the windshield. If you do determine the mist was coolant and not A/C refridgerant you can be sure as to what part needs repairing.
(I had a refridgerant leak in a late model car that caused mist to come out of the vents).
The members gave you some great removal advice.
(I had a refridgerant leak in a late model car that caused mist to come out of the vents).
The members gave you some great removal advice.
Thread Starter
Advanced
Joined: Jun 2013
Posts: 87
Likes: 12
Thanks. I'll check that. I've gotten this "mist" a few sporadic times over the last few years. And I've also driven it a good many times in the winter months (in PA) with the heater on and no "mist". And there is no visible water leak in the interior. And you are right, I don't want to tear apart something that isn't broke.
Le Mans Master
Joined: Jun 2019
Posts: 7,649
Likes: 2,466
From: Indiana
Pressure leak check the coolant system .
i could smell mine and it fogged the window
put in 2 shut off valves so you can help ac in summer and isolate to delay fix until convenient or u need heat
i could smell mine and it fogged the window
put in 2 shut off valves so you can help ac in summer and isolate to delay fix until convenient or u need heat
Last edited by interpon; Mar 5, 2026 at 05:49 PM.
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