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Pete, Pontiac Technician
Category: Pontiac
Satisfied Customers: 23885
Experience:  17 Years Pontiac Technician and training.
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2001 Pontiac Sunfire: firewall..rotated..the interior of the cabin

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2001 Pontiac Sunfire is leaking coolant from the firewall elbow pipe between the two A/C connections. I notice that when the cabin temp control is rotated to the extreme 'cold' position that there appears to be more leakage than if the control is at center or right (heat). There does not appear to be any leakage into the interior of the cabin. I don't want to prejudice your response, and I have no knowledge of the systems involved, but, it seems more like if it's leaking coolant more when the control is set to 'cold' that the issue might not actually be the core, but rather, is there a valve kind of thing that stops / bypasses the heater core in some way? it kind of seems to be working in reverse for it to just be the core. (ie: you'd expect it to leak more when 'heat' is selected if it was the core, wouldn't you)?

Hello,I will be glad to try and assist you with this,Welcome to Just Answer.


Where is this elbow pipe located?


Let me know,Thanks Pete!

Customer: replied 5 years ago.

on the engine side of the firewall, just below and between the two a/c pipe connections. it's a short (perhaps 1 inch) out and down kind of thing. there's nothing connected to the downward facing end of the elbow pipe. I think this is an overflow outlet from the things (eg: the heater core, and the equivalent for the cooling) in the passenger compartment, designed to prevent any leakage in the passenger compartment (which at this time, appears to be working as designed!).

O.k.,this is the heater box drain outlet,all vehicles have this outlet to drain any water that the ac evaporater develops inside the heater box.


If there is coolant leaking out of this then this is usually an indication thatthe heater core is leaking.This is common.By looking at the heater/coolant system components on this vehicle in my diagrams there is no other coolant component inside the heater case from where this drain is attached so the heater core is the only component that could be at fault here.


Your vehicle does not have a coolant shut off valve indicated in the diagrams,some vehicles have these and when cold is selcted the shut off valve will stop the coolant flow through the heater core which would stop the leak,but according to the diagrams I have here this vehicle does not have this.


You can double check this by looking at where the heater hoses enter the firewall and follow both of these hoses all the way to where they attach on the engine or radiator,if there is an electrical valve in between the firewall and the engine or radiator on these hoses then this would be a shutoff valve and this would be why there is no coolant leak when cold air is switched on.


Customer: replied 5 years ago.

interesting... so you seem to be saying that regardless of what the passenger cabin heat/cool setting is, that there's *always* water from the radiator passing through the heater core? is that correct?

Yes,with your vehicles cooling system the coolant is always flowing through the heater core,unless your system has the coolant shut off valve on one of the heater hoses going into the firewall.The coolant system diagram that I have looked at for your vehicle shouldnt have this shutoff valve unless it was installed after market.


Let me know,Thanks Pete!

Customer: replied 5 years ago.

Ok, well, I bought this car new, so it is completely stock in that regard. Sorry this is taking so long, but: can you offer an explanation as to why it would appear to be leaking more when the temp control is over toward the cold side (the A/C is not being turned on at this point, just the temp control rotated toward the cold).


Also, given what this appears to be (ie: problem with the heater core), what's going to be involved in getting it replaced? eg: easy, do it at home kind of thing? any 'gotcha's? that would mean I have to have a pro do the job?

The only thing I can think of as to why this leaks more when the heat is selected and not when cold is selected is possibly because the heater box temperature door for heat closes when turning to cold air,this may trap the leak inside the heater box and not show up leaking onto the ground or out of this drain tube.This has to be the only reason why this is acting the way it is since your vehicle does not have the heater shut off valve.


To replace this the entire heater box has to be removed from under the dash,this will involve draining and recharging the freon in the ac system,removing the entire dash assembly in order to gain access to all bolts and screws to remove the heater box/case.


This can be a difficult job and if you don't have a freon recovery machine then it is recommended to have a shop do this repair.


Below is the parts and labor cost of what you should expect to pay for this repair.



Parts OEM Part Price

Heater Core...............................................Part# XXXXX $219.04

Replace.....................................................6.5 hours labor +1.0 hours labor to remove and install freon

Does Not Include: Refrigerant Recovery Or Evacuate & Recharge AC System.

You might be able to purchase a heater core cheaper at an after market parts store.


Pete, Pontiac Technician
Category: Pontiac
Satisfied Customers: 23885
Experience: 17 Years Pontiac Technician and training.
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