It only leaks coolant when the heater is on..

[BDR1]

I've got a 2002 trailblazer...it's leaking coolant it seems from down the firewall maybe..but it only leaks when the heater is on...anyone have an idea what this could be..4.2 inline 6 motor...almost seems like it could be coming from around the reservoir tank...but only loses coolant when heater is on

 

[optimist]

I've got a 2002 trailblazer...it's leaking coolant it seems from down the firewall maybe..but it only leaks when the heater is on...anyone have an idea what this could be..4.2 inline 6 motor...almost seems like it could be coming from around the reservoir tank...but only loses coolant when heater is on

Sounds like the heater core to me or maybe a hose connection to the core.

 

[boneboy96]

Heater core or pin sized hole in hose. Smells up the car bad.

 

[BDR1]

No smell at all inside the car...if it leaks you can only smell antifreeze outside the car...also has to driven to get it to leak...crank it up and let if run it don't leak. ..just after driving for a bit...

 

[41mag]

If those are the same hoses i think they are, check the connections by the core on the firewall. There are plastic type connections with an o-ring in them. The connectors sometimes break, or the o-ring could leak.

Best thing to do is get a pressure tester and pump it up to check it with key on, engine off and heater on.
It can be tested with it running and heater on. Just beware of hot coolant !

 

[spistols]

Windshield doesn't fog up when heater is on?

 

[greg vess]

The heater and A/C box has a drain spout usually a rubber turn down in the engine compartment. That allows condensation to drain when the A/C is on. That is what you see after you have had the air on for a while and you get the puddle of water under the vehicle. So my be is the heater core or heater hose inside that box.
On older cars there was a cable actuated valve out in tbe engjne compartment that allowed water into the heater c6ore. Now its either electric or vacume actuated and it all happens inside that heater/air con box. Either way it wont be cheap to fix. There is the cost of the part but the cost of that pales in comparison to the labor getting to it. You have a considerable amout of dash that has to be removed in order to get to it. Shop around for prices. They have a book that gives them the labor hours for each job on each car but one shop might know tricks to do it faster and save you a few bucks.

 

[spistols]

If heater core, I have seen people cut out the firewall vs take out the pain in the ass dash.

 

[Grdbreaker]

Kell radiator Douglasville 770-942-2696 in business 50 yrs,family owned and good people,my woman is half owner,she will do you right.Sounds like a bad heater core, you can bypass it ,but you won't have heat/defrost(in 2-3 weeks you wont need it for 6-7 mths anyway) You can pressure test the system and find out pretty quick whats up with it.

 

[tas6691]

"If heater core, I have seen people cut out the firewall vs take out the pain in the ass dash."


Any one that would do that is an idiot.
Besides the fact cutting the firewall aint gonna help if the heater case has to be opened up to get the core out.