2004 Chevy Trailblazer Heater Core Leak

Tiny
DEREKJLARIVIERE
  • MEMBER
  • 2004 CHEVROLET TRAILBLAZER
  • V6
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
A mechanic friend of mine bypassed the heater core in my vehicle because I was told by multiple mechanics that the core was leaking. Still, even after the bypass, I have a leak behind the passenger's side wheel. The coolant only leaks when the SUV isn't running. Once the car is turned off, the leak begins only about a minute later. It comes from a valve.
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Wednesday, February 17th, 2016 AT 11:21 AM

19 Replies

Tiny
JOHNNYT73
  • EXPERT
I would take it to shop and have them pressure test it to see where its coming from.
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Wednesday, February 17th, 2016 AT 11:27 AM
Tiny
DEREKJLARIVIERE
  • MEMBER
To be more specific, here is where the leak is coming from. The black overflow "nipple" valve.
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Wednesday, February 17th, 2016 AT 11:29 AM
Tiny
JOHNNYT73
  • EXPERT
That to me looks like the a/c evaporator drain.
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Wednesday, February 17th, 2016 AT 11:31 AM
Tiny
JOHNNYT73
  • EXPERT
Are those hoses going into the firewall?
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Wednesday, February 17th, 2016 AT 11:32 AM
Tiny
DEREKJLARIVIERE
  • MEMBER
Yes, but there is no sign of coolant inside the vehicle or even a smell in the upholstery in the back.
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Wednesday, February 17th, 2016 AT 11:33 AM
Tiny
DEREKJLARIVIERE
  • MEMBER
If it is the A/C evaporator drain and it's leaking steadily, is there a quick fix for that?
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Wednesday, February 17th, 2016 AT 11:34 AM
Tiny
JOHNNYT73
  • EXPERT
Im trying to get a sense of where you are positioned in this photo. So I can get my bearings straight on what I'm looking at.
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Wednesday, February 17th, 2016 AT 11:37 AM
Tiny
DEREKJLARIVIERE
  • MEMBER
I'm lying on my back underneath the back of the truck, outside of the muffler.
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Wednesday, February 17th, 2016 AT 11:40 AM
Tiny
JOHNNYT73
  • EXPERT
The muffler? So these hosessions go to the rear of the truck?
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Wednesday, February 17th, 2016 AT 11:54 AM
Tiny
JOHNNYT73
  • EXPERT
Hoses*
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Wednesday, February 17th, 2016 AT 11:55 AM
Tiny
DEREKJLARIVIERE
  • MEMBER
Yes, all of this literally right behind the rear passenger's side wheel.
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Wednesday, February 17th, 2016 AT 11:55 AM
Tiny
JOHNNYT73
  • EXPERT
Ok, that looks to be the a/c drain tube for the rear evaporator. What color is the fluid that comes out, and how much?
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Wednesday, February 17th, 2016 AT 12:04 PM
Tiny
DEREKJLARIVIERE
  • MEMBER
It's definitely coolant. It's green, and after a week or so, I am running way low. It drips pretty steadily when the engine isn't running. If I let it sit for a couple days, it's nearly empty.
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Wednesday, February 17th, 2016 AT 12:16 PM
Tiny
DEREKJLARIVIERE
  • MEMBER
Any idea about what I can do to stop the leak in the short term?
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Wednesday, February 17th, 2016 AT 4:41 PM
Tiny
KEN
  • ADMIN
Are you sure the heater was bypassed? Could this be residual leakage? Coolant still in the core?
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Tuesday, February 23rd, 2016 AT 12:58 PM
Tiny
DEREKJLARIVIERE
  • MEMBER
It's been doing this for about three months. It's a slow leak, but if it were residual, it should have run off by now.
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Tuesday, February 23rd, 2016 AT 1:50 PM
Tiny
KEN
  • ADMIN
Does the car have rear air?
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Wednesday, February 24th, 2016 AT 7:38 AM
Tiny
DEREKJLARIVIERE
  • MEMBER
Yes it did, but the bypass shut it down, heat and air both.
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Wednesday, February 24th, 2016 AT 12:54 PM
Tiny
KEN
  • ADMIN
This is a weird one alright, the car must have the lines still full and its residual. There is no other thing I can think of, please let us know if it stops.
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Wednesday, February 24th, 2016 AT 3:20 PM

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