Smoke coming from defrost vents in dash

[IDI_Journeyman]

Hello oil-burners, I have a 1985 F250 4x4 with a 7.3 idi ZF5. Once the trucks at operating temperature smoke starts to come out from all of the defrost vents from the top of the dash. Has anyone else experienced this? I'm assuming I need to replace my heater core or something Along those lines... doesn't smell like burning wires.

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[nostrokes]

Does it smell like antifreeze? I'd say heater core.

 

[IDI_Journeyman]

not too familiar of what antifreeze smells like do I have to pull the dash off to replace the heater core? Iv never done this before

 

[DaveBen]

No.just remove the glovebox and the heater core is behind the panel. Easy.

 

[hadley000]

doesn't smell like burning wires

Is it smoke or water vapor?

what antifreeze smells like

Is the coolant level going down? If it doesn't smell electrical, I'd say it's the heater core too.

 

[IDI_Journeyman]

It kind of looks like water vapor. It has a small drip but I can't really tell where it's coming from. It looks like it's dripping off a gromet from the firewall on the passenger side. I know for a fact the leak isn't from any freeze plugs or any hoses Iv replaced (top& lower rad and hose from water pump)

 

[hadley000]

dripping off a gromet from the firewall on the passenger side

The heater core is on the passenger side behind the glovebox. They're like $30 and pretty easy to change from what I remember.

 

[nostrokes]

not too familiar of what antifreeze smells like do I have to pull the dash off to replace the heater core? Iv never done this before

Pop open your overflow bottle and take a whiff pretty distinct smell, kinda sweet smelling.

You do not have to pull the dash. Clamp your heater hoses off before pulling them from the fittings so you don't loose all your coolant. Pull the glove box out, no screws just undo the little strap, squeeze the sides and roll down towards the floor. 6-8 screws holding the cover on. Nothing holding the core in but gravity. Takes about an hour if you take your time nothing major, that's 1 thing Ford did smart on these older trucks.

 

[Clb]

Heater core sounds right...Search out heater cores on here for a good primer.

 

[chris142]

30 min max to change the heater out.

 

[BeastMaster]

If its the heater core, at this time of year, get condensation on the windshield? I just had my heater core go out, and it steamed up the windshield so bad I could barely see. Even after I had removed the radiator cap so as to stop the pressure buildup. The venting of pressurized hot water inevitably results in a lot of steam.

Otherwise, you may have a PSOM failing. Seems there is a varistor on the PCB that once it takes too many hits from alternator load-dumps, it shorts out and takes part of the PCB along with it.

If you suddenly notice your overdrive light flashing, your transmission hard-shifting, or your speedometer malfunctioning, there's your problem.

 

[Macrobb]

I want to point out that if it smelled like actual smoke of some sort(not electrical smoke and not coolant), it could be leaves or a mouse nest burning off of the blower load resistor.

 

[Oil_In_The_Gas]

My vote is the heater core too. However I've had leaves get into the heater fan resistors and when the fan speed was on the lowest setting started to burn the old dead leaves and started to smolder and smoke. Just takes 2 screws to pull the resistors from the heater box to make sure.

 

[Psolver]

what is a psom

 

[DrCharles]

Google is your friend!
Programmable Speedometer Odometer Module.

More likely to be heater core (if coolant vapor) or smoldering leaves, as already pointed out. My '84 gasser actually set the leaves on fire one night, scared the crap out of me. Think it blew the fuse for the dash lights as well as the one built into the fan resistor pack... after that I was more careful to keep the blower housing clean!