My defroster covers interior with moisture

[larryboy_3t5]

Does anyone have an idea why this is happening? I don't smell antifreeze, can't find any leaks, and my windshield doesn't leak. Carpets are bone dry. Can't find any moisture in the cab. But when it rains, and I turn the heater/defrost on it covers the entire interior with moisture. Dash, windows, gauges. It is blowing hot and there is strong air coming from the defrost vents. If I don't turn on the heater at all it is not as bad. I also notice that when I wash the truck, I get small circles of moisture just above the defrost vents. I'm stumped. This truck was stored in a heated garage it's whole life, 17k original miles. It's like a time capsule. The rubber is all very soft, it was like buying a one or two year old truck. everything works like butter. Windows, cold air vents, door latches. This is the only thing that seems out of sorts.

[special-K]

Your heater core is shot. It leaks coolant into the heater box creating steamy air being blown. You are better off using your wing vents and a towel until you replace it

[StingRay]

Yup what K says.

[VetteVet]

I don't think it's the heater core for four reasons.

1. He doesn't smell anti-freeze- I've had three vehicles with leaking heater cores and the smell is unmistakable.

2 He hasn't said anything about low coolant.

3. The carpets are not soaked. Mine were every time.

4. It only seems to happen after a wash or heavy rain.


This sounds like a leak into the heater box maybe a drain hole is plugged, If he has AC there should be a drain for condensation in the lowest part of the system with a rubber drain tube to the outside, or the heater core box gasket isn't sealing.

[larryboy_3t5]

Bought the truck in Portland, OR three weeks ago. Drove it home to Brentwood, CA. (East edge of the S.F. Bay Area) So I've only had it for three weeks and put 1000 miles on it. Coolant seems to be staying put so far. It doesn't have AC. Plan to pour some water in the cowl vents today and check if it's draining properly.

Thanks for all the input so far.

[NoNeck]

Just an idea, but you might check the rubber grommet where the antenna coaxial cable goes through the cowl. I had a dried and cracked grommet that allowed water to seep down the cable and drip into the GM under-dash air conditioner unit. It also happened right after I washed the truck or when it was raining. I had condensation out the vents when the AC was turned on.

POP

[In The Ten Ring]

I had exactly that happen in my 1975 Pontiac Bonneville. I was driving home from college in 2001 and the defroster blew moisture onto the windshield.

I had to get a new heater core.

I guess water could be getting into the system though from outside, like the guy said he had happen with his antenna grommet.

Anyone else want to weigh in?

I do know that to remove your heater core you'll have to have your hood off along with the passenger side hood hinge. Fortunately the heater box is easy to take apart and replace the core, I did that to mine.

[68350]

Im agreeing that its the heater core. I had simolar symptoms and it was a bad heater core.

[scooterpimp]

If it only happens after rain/outside water. Happens ,Not seein it being a heater core? Try riding around with heat/defrost on dry day for giggles?

[jerry moss]

i've seen this truck in person and it is beautiful inside and out. my first thought was heater core too but it only happens when water is on the outside and like Larry stated-the coolant level isn't going down and the unmistakable coolant smell is not present. there has to be a small leak somewhere from the outside getting in. now, Larry, where are the pics so the rest of the board members can drool over this jewel.

[special-K]

I responded without reading the info much at all. I thought I saw you could smell anti-freeze and stopped reading there, when I was already thinking heater core. I've seen them leak without getting the cab wet, though.
I'd guess it's a seal to your heater or that antenna seal

[franken]

Is the coolant water, or a mix?
If it only happens when it rains maybe a leak between the body and the heater system?

[larryboy_3t5]

Sorry Jerry. I can't figure out how to edit my signature. How am I supposed to post pictures?

[larryboy_3t5]

So I poured water in the cowl vent on both sides. It drains beautifully. It is a beautiful 80 deg today and sunny. I ran the defrost on high and it fogged all the windows but not to near the degree it did on the rainy day. All the windows fogged then the windshield started to defog above the defrost vents. Absent was the heavy moisture on the rest of the interior surfaces. The seal between the heater box/fan and firewall is soft and pliable and appears in really good shape. The weather strip between the cowl and hood is cracked and misshapen. I ordered a new one today. I'm busy working the rest of the night but tomorrow I will try pouring water across the front of the cowl while running the defroster on high. See if that replicates the symptoms. If not, I guess I can remove the cowl vent for the fist time in it's life ): I'll keep updating the progress. And maybe get Jerry to come over and show me how to post pictures. ._.

[larryboy_3t5]

????

[larryboy_3t5]

Son, of, a,..........hey, I got it (:

[larryboy_3t5]

Take that Jerry!

[larryboy_3t5]

And the coup de grace........

[larryboy_3t5]

Believe it or don't

[joeydurango]

Holy mackerel, that thing is beautiful. Congrats for sure. Enjoy!

[jerry moss]

[joeydurango]

Looks like the garage couldn't keep the cab mounts from rotting a bit, regardless of mileage... but that's an easy fix!

See, now that you've posted photos, your defroster issue is forgotten, and we're all just going to look at your truck.

[FirstOwner69]

I was watching that one on eBay and drooling! Same color as my 69, but mine doesn't have the white top. I'm glad to see a forum member got it.

[larryboy_3t5]

I know, I should be working. But...

The story I got from the broker who bought the truck from the widow of the original owner is this:

Oscar, the original owner, ordered the truck in December of 1968 from Appleway Chevrolet in Spokane, Washington. He took delivery, around the same time he ordered a slide in camper in January 1969. He wrapped the camper in foam before installing it which explains the condition of the original paint in the bed. He parked it in a heated garage, with the doors ajar so the weather strip would not get crushed, and only took it out to go camping. (I'm sure camping was a hoot with this guy. He probably spent the whole trip waxing his baby.) He died Feb. 6, 2014 at age 92.

The broker also had the camper and it looked just as pristine.

My buddy, Eric, and I flew to Portland to buy the truck then drove it home over two days. We stopped in Redding, Ca. long enough to enter it in one of the many small car shows during Kool April Nights.

I was able to retain the original title issued 1/15/69. I also have the build sheet with seat spring imprint, protect-o-plate, owner's manual, and the pre-delivery service and adjustment check sheet. It also came with an instruction card on how to document an accident. Not sure if the dealer gave these out or it was an insurance company. There is no indication of either.

The placards you see on the trans hump look to have been made by a trophy shop or something similar. They are plastic with a faux wood grain and are engraved to read "G.W. 10,000". On the back side there is a decal that reads "8,000 GR". Not sure what that's about. I remember as a kid seeing some of the grey beards driving these rigs with similar decals on the side. Anyone know what that was for? The GVW is listed on the VIN plate as "7500". BTW, these placards were attached to the fenders with screws just above the "Custom Camper/20" emblems. The holes are still there but the paint was not damaged.

For your edification, the blue can that is plumbed to the PCV line is a Marvel Mystery Inverse Oiler. Had to look it up. Allows an adjustable amount of Marvel's top end lube to get sucked into the intake and burned. Supposedly to lubricate the valves. Oscar also added a high energy ignition, spots, bumper guards, driving lights, SW gauges for vacuum, trans oil temp, and oil pressure, a trailer brake, air horn, gun rack, and CB radio (removed before sale to my dismay). I can see some leftover hardware, holes, and brackets for side steps and mud flaps. There's a few scrapes on the top of the bed sides where the camper made contact and a couple of buggered spots on the rear window trim from same. Also stone chips on the front of the hood that have been touched up and some in the windshield as well. But overall it looks like it's no more than a couple of years old.

I found Oscar's obituary online. He worked for Hyster as a field rep and service manager and sounds like he was an upstanding, hard working dude.

If you're listening Oscar, I'll take good care of her. She'll be pampered but used. Once I figure out a way to protect the paint in the bed, she'll be hauling materials for projects, car parts, and two old dogs who will be loving life with the wind in their hair, er, fur. TTFN.

[El Dorado Jim]

Nice rig !!! so cool you know all the history of her!