heater core pinhole?

The inside of the windsheild of my '92 Accord started to fog up sometimes through the defrost vent on the passenger side after the car had been running awhile, and I also noticed smell of coolant. There is no wetness that seems to be developing on the carpet below, so I figured I probably have a tiny pinhole in the heater core, enough to mist out or very fine spray instead of a bigger leak.
For this vehicle, replacement of the heater core is a big deal, apparently requiring removal of the steering column and a big part of the dash, etc.
I have a new heater core, but the local shops quote very expensive for them to do the job, apparently labor time is estimated around six hours or something.
Some suggested I try Barrs leaks to see how that would work. I did, and it seemed to work for a while I guess but now the problem is back.
Before I bite the bullet and either start trying to dismantle the dash myself or decide to take it to a shop and pay the big bucks to replace the core, are there any suggestions or comments, especially regarding how I might be able to determine in advance whether my heater core does in fact have a pinhole as I assume?

 

I would suggest trying Alum-a-Seal, it worked very well for me just make sure to get the brand name and not some lookalike. Have a good one. Geo

 

I recall that when I first considered adding a stop leak product for this issue and sought advice that a third of the people said to use Alumaseal only and cursed Bars Leaks, a third of the people said to use Bars Leaks only and cursed Alumaseal, and the other third said either might work but the most sure fix would be core replacement.
Any comments by my description on whether my issue as described could be anything else other than a pinhole leak in the core, before I proceed in core replacement job?

 

Heater cores are almost always a royal pain to replace. You can bypass the heater core - just loop the heater hose back to the engine. If this stops the leak [sounds like it will] you know it is in the heater core. Of course this also leaves you without heat - and summer is gone

 

I was shown an example many years ago(40+), Alumaseal stays in suspension in the cooling system and if/when the area starts to leak again it will reseal it. I had an 82 Toyota Supra with a core leak and took it to the dealer and was told they didn't want to do it because it was such a big job with electrical issues, I dumped a $1.98 tube of Alumaseal in and it lasted until I sold the car, about 3 years later. Have a good one. Geo

 

Okay Geo you talked me into trying Alumaseal, but do you think that if I add it to the existing coolant to which I added the Bars leak product eight months ago that it would be okay to do so?
As a side note, I inquired with one of the better auto shops in my area and they told me it was likely that none of their mechanics would be willing to take on the job of replacing the heater core in this vehicle because its such a pain.
thanks

 

I think I would drain the cooling system, bar's seems to have some goo that I don't think the Alum little flecks would like. I called the company a long time ago, they were in Arizona(I think) and they were adimate about their product and how to use it, which was, put it in, drive the auto and the leak will stop, then add another 1/2 tube. Have a good one. Geo