possible heater core issue
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 769
Likes: 1
From: Columbia TN
possible heater core issue
I thought I'd ask the guys here to see if I have a heater core issue. My car (2004 Z06) is quite mod'd so I texted the shop owner some of the symptoms I was having but I didn't exhaust the list. His and my belief is it is the heater core. The trouble is I was researching here and now I'm not sure if I told him everything I should have.
Symptoms:
-coolant smell while driving
-mildly foggy windshield (vents, no a/c, were set for recirculating air to come from the upper vents but not the defrosting vents by the windshield) It was around 45° outside and I was driving with the windows down and the heat at 84°. Not abnormal in TN to have a foggy window in these conditions, but the coolant smell had me nervous.
-fogginess went away with the windows halfway up and the defroster on. Didn't take that long either.
-no leaks that I can tell on the outside. New radiator within the last 18 months.
-no visible leaks in the car or on the floorboards either
I saw a post about a bad coolant reservoir tank cap and a couple of other things and now I'm not so sure I need to replace the heater core. The engine temps are fine and the coolant in the reservoir doesn't look low.
Any other suggestions?
Symptoms:
-coolant smell while driving
-mildly foggy windshield (vents, no a/c, were set for recirculating air to come from the upper vents but not the defrosting vents by the windshield) It was around 45° outside and I was driving with the windows down and the heat at 84°. Not abnormal in TN to have a foggy window in these conditions, but the coolant smell had me nervous.
-fogginess went away with the windows halfway up and the defroster on. Didn't take that long either.
-no leaks that I can tell on the outside. New radiator within the last 18 months.
-no visible leaks in the car or on the floorboards either
I saw a post about a bad coolant reservoir tank cap and a couple of other things and now I'm not so sure I need to replace the heater core. The engine temps are fine and the coolant in the reservoir doesn't look low.
Any other suggestions?
Le Mans Master
Joined: May 2005
Posts: 6,366
Likes: 249
From: Fort Lauderdale, Florida
Sounds like a new heater core is in your future. I'm replacing the one in my truck for the same reasons as I write this. Sorry, it's a bitch of a job but maybe the Vette isn't as bad to do.
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
Here is info on removing the dash. Bag and tag all the various fasteners. Not that bad to do.
https://www.corvetteforum.com/forums...post1590759402
http://tech.corvettecentral.com/2013...-dash-removal/
Mr. Sam
https://www.corvetteforum.com/forums...post1590759402
http://tech.corvettecentral.com/2013...-dash-removal/
Mr. Sam
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Instructor
Joined: Feb 2006
Posts: 143
Likes: 3
From: Wichita KS
Looks like I am in the same boat. Went to drive my 2002 Z06 and noticed a small amount of fluid under the car. Got underneath and the front edge of the floor board was wet. Checked the passenger side carpet and it seemed ok, but also had the fogging of the windows. I am planning on starting the repair this week. My temperature control has been acting up as well (not able to adjust the temperature in manual mode - either is full hot or full cold), so I am going to look at the blend door actuators while I have everything apart (the last time I checked, I didn't have any codes).
Doesn't appear to be a fun job...
Doesn't appear to be a fun job...
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
IF,,,,,,,,,,,, you have a heater core leak,,, you USUALLY wont see any coolant on the inside of the car. There is a HVAC AIR BOX DRAIN on the passengers side fire wall. It WILL or SHOULD leak out of that drain onto the ground.
HOWEVER,,,,, That being said, It may be such a small leak that you wont really see a big puddle under the car..
If you have an operational AC, run the car inplace with the AC ON Full Tilt, doors and windows open and you should see condensation from that drain. Put a pan under the car and collect it and see if there is any coolant in the condensate.
OR
My recommendation would be to externally pressurize the cooling system over an extended period of time and see if you have any collectable amount of coolant coming out of that drain on the passengers side fire wall.
Its directly AFT of the passengers cylinder head. If you have headers, its a BITCH to get to under the car.
HOWEVER,,,,, That being said, It may be such a small leak that you wont really see a big puddle under the car..
If you have an operational AC, run the car inplace with the AC ON Full Tilt, doors and windows open and you should see condensation from that drain. Put a pan under the car and collect it and see if there is any coolant in the condensate.
OR
My recommendation would be to externally pressurize the cooling system over an extended period of time and see if you have any collectable amount of coolant coming out of that drain on the passengers side fire wall.
Its directly AFT of the passengers cylinder head. If you have headers, its a BITCH to get to under the car.
Instructor
Joined: Feb 2006
Posts: 143
Likes: 3
From: Wichita KS
Good points, Bill.
The small puddle under my car is definitely coolant. I am going to dig into it when I have time to verify that it's coming from the AC condensate drain. That being said, my windows fogged up when I drove my car this weekend and ran the heater. I haven't run the AC in a while and the car hasn't seen rain in a long time, so there isn't any other source for the dampness. The odds are that it is coming from the heater core, but I want to look at all of the connections, hoses, etc. just to be sure after I pressurize it.
The small puddle under my car is definitely coolant. I am going to dig into it when I have time to verify that it's coming from the AC condensate drain. That being said, my windows fogged up when I drove my car this weekend and ran the heater. I haven't run the AC in a while and the car hasn't seen rain in a long time, so there isn't any other source for the dampness. The odds are that it is coming from the heater core, but I want to look at all of the connections, hoses, etc. just to be sure after I pressurize it.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Good points, Bill.
The small puddle under my car is definitely coolant. I am going to dig into it when I have time to verify that it's coming from the AC condensate drain. That being said, my windows fogged up when I drove my car this weekend and ran the heater. I haven't run the AC in a while and the car hasn't seen rain in a long time, so there isn't any other source for the dampness. The odds are that it is coming from the heater core, but I want to look at all of the connections, hoses, etc. just to be sure after I pressurize it.
The small puddle under my car is definitely coolant. I am going to dig into it when I have time to verify that it's coming from the AC condensate drain. That being said, my windows fogged up when I drove my car this weekend and ran the heater. I haven't run the AC in a while and the car hasn't seen rain in a long time, so there isn't any other source for the dampness. The odds are that it is coming from the heater core, but I want to look at all of the connections, hoses, etc. just to be sure after I pressurize it.
You could DOUBLE CHECK and feel under all the carpets and make sure that there isn't any dampness there.
IF that drain plugs up, the condensate will build up and drain into the passengers foot well....
Last edited by Bill Curlee; Feb 2, 2016 at 06:59 PM.
Instructor
Joined: Feb 2006
Posts: 143
Likes: 3
From: Wichita KS
Yup, it's the heater core. Confirmed last night.
FYI to everyone - Chevy has discontinued the heater core, but there are a lot of aftermarket ones out there. Be careful though - many of them are junk. I work in the HVAC industry and there are a lot of Chinese manufacturers of these heat exchangers with questionable quality. The original radiator in my wife's Accord sprung a leak after 15 yrs. We were going to get a new car in the next year, so I replaced it with a radiator from O'Reily's. It sprung a leak in the first week, so I ended up putting another Honda radiator in it, with no problems. It probably came from China too, but at least it went through Honda's quality system and approval process. Replacing the heater core in this car is not something I want to do twice. I would rather spend the money on a quality piece and not worry about it.
FYI to everyone - Chevy has discontinued the heater core, but there are a lot of aftermarket ones out there. Be careful though - many of them are junk. I work in the HVAC industry and there are a lot of Chinese manufacturers of these heat exchangers with questionable quality. The original radiator in my wife's Accord sprung a leak after 15 yrs. We were going to get a new car in the next year, so I replaced it with a radiator from O'Reily's. It sprung a leak in the first week, so I ended up putting another Honda radiator in it, with no problems. It probably came from China too, but at least it went through Honda's quality system and approval process. Replacing the heater core in this car is not something I want to do twice. I would rather spend the money on a quality piece and not worry about it.
Heel & Toe
Joined: Jun 2022
Posts: 15
Likes: 0
From: Norfolk, VA
Did you end up replacing the heater core? I have the exact same symptoms, no wet floorboards, just antifreeze smell and fogging up of windshield near the front defroster vent. 2004 C5 with 130k miles.
