Question about 1988 GMC S-15

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Heater Coil Leak

Coolant leaking into passenger compartment from floor heater vents. Causes the windows to fog up even when defroster is not running. Suspect heater coil leak in heater box. How can I fix this myself?

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Hey mad40bx that will be your heater core,,just pick up a new one and grab a haynes or chilton manual for your truck if you are not familiar with the procedure its not that bad, if you dont need it fixed immediately take the 2 hoses off from the firewall (One is supply and one return) and couple them together this will bypass the heater core until you are ready to fix it, good luck

Posted on Nov 10, 2008


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1 Answer

How can I check to see if the heater core is bad, please help

If the heater core is bad you will most likely have a coolant leak inside the car on the passenger floor area or you will get a sweet smell along with the windshield fogging up on defrost or whisps of smoke/steam from the vents

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What causes smoke to come through the vents on a 2004 Jeep Liberty 5 speed manual 3.7L engine?

It will most likely be whisps of steam you see through the vents often accompanied with sweet smell. The heater core is usually the culprit and is leaking. Any coolant stains/wet marks on the passenger floor. Does the windshield fog up when on defrost. All signs of a leaky heater core

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I have a 2004 Dodge Dakota inside widows fog up no leak in passenger side floor board but defroster clears the windshield in the center so you can drive and all windows will fog

It does sound as though you have a coolant leak causing the fogging. Do you get a sweet smell from the heater vents? That's a dead giveaway. Often the coolant does not get to the floorboard if the leak makes it to the A/C condensate pan. Then it just goes to the ground thru the firewall. Watch for loss of coolant in the system. If you have an appreciable loss, then you should look at the heater core as the most likely cause.

Dec 22, 2014 | 2004 Dodge Dakota

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1998 dodge durango window fog

may be a blocked vent in the windscreen vents. could be at the windscreen end or at the controler in the heater. if you dont have a pollen filter fitted rubbish from the road i.e leaf's can get in and block it up.

Dec 08, 2013 | Dodge Cars & Trucks

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My 2001 jeep grand cherokee has a dark mist/smoke coming out of the vents, and defroster. But, the heater works fine. What could it be?

DO NOT USE STOP LEAK!!!!!! That stuff has no brain so you cant tell it to plug only specific leaks. It will go for the easiest hole to plug which can be a water port in the cooling jacket for the cyl heads. replace the heater core. Fix it right or bypass but please please please do not use anything that will stop a leak

Dec 22, 2012 | Cars & Trucks

1 Answer

Climate control system blows only through the defroster vents and not through the passenger compartment vents; the windshield fogs in high humidity and windshield wipers are necessary to clear the fog. ...

If the fogging is plain moisture and not coolant (it would take on a green hue and you would smell coolant if this is the case) than the issue is with the blend door actuator. This component diverts air from the window, to the vents and floor. You may have a "stuck" door or a defective blend door. If it is coolant you are seeing (smelling), you may have a bad heater core. When bad, a heater core will dispel green vapor through the defroster vent.

Assuming the problem is merely the blend door, you may be able to free the part (if it's stuck) by locating it (usually under the glove box or between the glove box and middle console.

Jul 31, 2011 | 2006 Mercury Grand Marquis

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You didn't specify what type of vehicle.
If you have very poor air flow out the vents, later model vehicles have a hepa filter or cabin filter in line form the blower motor to the vents. It can be plugged quite easily and drastically cuts down the air blown into the vehicle. Check to see if they are plugged. Secondly, Check your coolant level in the rad and reservoir. If the windows fog up when cold and air flow is good it could indicate a leaking heater core. Check the passenger side floor for signs of coolant again I don't know the type of vehicle, some heater cores are located at the firewall under the hood.

Jan 31, 2011 | Oldsmobile Intrigue Cars & Trucks

1 Answer

Coolant leaks into passenger side floor and haze comes out of vents

usually when this happens it is the heater core that is leaking. does the windshield get fogged with defroster on!! if so its the heater core. good-luck and have a good day.

Sep 21, 2010 | 2005 Pontiac Grand Prix

5 Answers

Heater immediately fogs all windows and there is a sweet odor in the cab of 2003 Buick Rendezvous, defroster works fine, but will not clear the windows after heat is put on

Sounds like a possible heater core failure(hole in it) the smell indicates to me the coolant(anti-freeze) is leaking into the passenger compartment.
Check the carpet in front of the front passenger seat for moisture, this would confirm heater core leak.
Good luck !

Jan 28, 2010 | 2003 Buick Rendezvous

2 Answers

Water accumulates on the floor in the passenger rear

your heater core is going out on the car...its leaking water into the car

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