[dataway]

I was making the first tentative shakedown tests on the freshly restored 68 GTO and I noticed some condensation showing up inside the windshield on the passenger side aligned with the defroster outlet.

I'm assuming a heater core leak. The vapor is not coming out of the defroster vent, it's sneaking past the defroster vent gap to the upper dash ... I know because it's only on the passenger side.

Heater core is original, it was in great shape, I vacuum tested it, but did not pressure test it. I think it's leaking from a tank ... if it was leaking from the fins it would fog the whole windshield when I turn on the defroster.

Engine cooling system holds pressure when hot for what seems to be the normal amount of time, so it must be a small leak.

I've resigned myself to the fact I'm probably going to have to pull off the inside HVAC box and replace it ... but I was also wondering ....

There are some respected voices on the forum that have high regard for stop leak products like "Barts" (?). Would that be an option? I have no real experience with them, a bit hesitant considering new engine, new recored (expensive) original radiator etc.

So far no moisture showing up on the carpet etc. Was thinking about trying to locate a place to drill a 1/8" weep hole in the bottom of the case to check for coolant standing in the bottom of the case.

What do you think?

[77 TRASHCAN]

New core time, period......

[25stevem]

I would try 1/2 a bottle of the Bar's leak first and see where that gets you.

[OCMDGTO]

When mine was leaking I had a puddle on the floor. I would confirm the leak before I tore it all apart. Maybe take out the glove box, etc for a better look?

[dataway]

It's definitely a small leak, engine has to be up to temp ... and it takes about five minutes to start fogging a 1/2 square foot of windshield.

At first I was hoping it was left over moisture or something on the core from this summers humid days ... but I gave it plenty of time to cook off and it would still come back.

I'll be checking inside for any sign of moisture today. That's why I want to figure out a place to drill a tiny weep hole ... anything comes out I know I have a problem. But might not work since I'm pretty sure the leak is in one of the tanks .. if it was in the finned section it would immediately fog the whole window when I turn on the defroster. I'm guessing all the abuse stuffing that thing in place and getting the outlets in place and muscling hoses on them cracked the 50 year old solder.

[GTOLou]

Good time to tap/plug the fitting on the timing cover and not connect it!

[Goatracer1]

Stop leak does work but only for a while. It will start leaking badly at the worse possible moment. If you don't need the heater by pass it at least so you can use your car.

[will slow gto]

If I recall the metal comprising the heater core is much thinner than the radiator. Since it’s the original, I wouldn’t bother with the Barr’s and gumming up your block and radiator. I know you’re really close but I would make the replacement now. You will want a heater/need a defroster some time soon. Bite the bullet and fix it.

[Schurkey]

Air conditioned? Is the evaporator drain hose plugged?

Dear Old Dad bought a '98 Monte Carlo. Hardly ever drove it. Parked outside--no garage. Had moss growing out of the exterior trim when I'd visit each summer.

Eventually, the evap drain duckbill plugged. I knew there was water in the evaporator case, because with every left-hand turn, the water would slosh to the right and get whipped-up by the fan squirrel-cage. It'd blow mist out of the ducts.

Pulled the duckbill off the nipple, got over a quart of water spilling out. Jacked-up the rear end, and even more came out. Carpet never got wet. I guess the heater/AC box was watertight.

[dataway]

Well, does have AC, but it doesn't work .. and a new duck bill

Guess I'll order a new core ... luckily the passenger seat is still out as I wanted to make sure I had room to move around in case anything came up ... and something has come up.

Is the Ames 68 core a good choice? I think the 68 with AC uses a unique core (?).

Thanks for the responses.

[Ram Air IV Jack]

Originally Posted by dataway

Well, does have AC, but it doesn't work .. and a new duck bill

Guess I'll order a new core ... luckily the passenger seat is still out as I wanted to make sure I had room to move around in case anything came up ... and something has come up.

Is the Ames 68 core a good choice? I think the 68 with AC uses a unique core (?).

Thanks for the responses.

Do not use an aluminum heater core!! Make sure you use a copper and brass unit. I replaced my heater core years back and the radiator shop people told me this. There has been discussion on PY about this subject so you may want to look that up!! 3M makes a sealing rope caulk that works great when resealing the core housing under the hood.

Good luck!!!

[will slow gto]

Originally Posted by Ram Air IV Jack

Do not use an aluminum heater core!! Make sure you use a copper and brass unit. I replaced my heater core years back and the radiator shop people told me this. There has been discussion on PY about this subject so you may want to look that up!! 3M makes a sealing rope caulk that works great when resealing the core housing under the hood.

Good luck!!!

X2. I ordered one years ago from Rock Auto and as soon as I held it in my hand I knew something wasn’t right since it was half the weight of my original. What Ames sells is much closer to the mark.

[dataway]

Yep the Ames unit appears to be copper and brass.

Looks like I have to pull my old one first and see if it's 2" or 2.5"

[indymanjoe]

I had to transfer a strap off my 72 HC as the new one didnt have it..fwiw

[BB70]

Check into finding a radiator repair place and have that one fixed.

[tjs72lemans]

I know it's hind sight, but I'm sure you're wishing now you would've replaced it while it was out. When I restored my car with AC, there was no way I was going to chance how much life was left in the core (it looked good). Messing with that box on the firewall side on my 72 was something I didn't want to look forward to, to replace a leaky core.

[dataway]

Yep, I certainly do wish that Twice ... once when I put in the interior case, and once more when I put the right fender on I said to myself .. I hope I never have to get to that stuff again.

I think on my 68 I only have to remove the inside case ... which probably means also the radio, glove box, ducks etc. ... but I have all winter to do it now.

[HWYSTR455]

The 442 'duck bill' drain part would get stuck closed from header heat, so I used a small section of aluminum hard line, stuck it in the end, and zip tied it in place.

Condensation in the case and small case leaks would build up moisture/water, especially from washing the car and driving in rain.

Anyway, the 442 has an aluminum heater core in it, and I have no problem with if for over 7 years, and that car was parked outside and driven in rain all the time. But, I do use aluminum-safe antifreeze (due to aluminum heads).

You have to remove a fender to do a heater core? Should be able to just remove the inner fenderwell if that's what needs to happen. The fan holds the outside case in place while you remove the inside case, no?


.

[Schurkey]

Aluminum heater cores have been "a thing" for decades. GM put aluminum heater cores in the '88--~'98 GMT400 trucks. I don't doubt that they were in use--somewhere--long before that.

If the thing fits, there's no reason it wouldn't work just fine.

[grivera]

Originally Posted by HWYSTR455

The 442 'duck bill' drain part would get stuck closed from header heat, so I used a small section of aluminum hard line, stuck it in the end, and zip tied it in place.

Condensation in the case and small case leaks would build up moisture/water, especially from washing the car and driving in rain.

Anyway, the 442 has an aluminum heater core in it, and I have no problem with if for over 7 years, and that car was parked outside and driven in rain all the time. But, I do use aluminum-safe antifreeze (due to aluminum heads).

You have to remove a fender to do a heater core? Should be able to just remove the inner fenderwell if that's what needs to happen. The fan holds the outside case in place while you remove the inside case, no?


.

I thought all coolants sold today are safe with aluminum components- do you know which ones aren’t?