Heater core leak
 

I have a 1940 coupe and the heater core has a small leak.What are the pros and cons on using KSeal to try to stop a leaking heater core? As far as I know no sealer has been used before. I’m concerned about engine water passes and the core itself due to the size of the core openings. Any advice would be appreciated. Thanks in advance and remember Pearl Harbor today.

Re: Heater core leak
 

I think it depends on how long the heater core has been in there. If it's an original or of unknown age, I'd remove it and repair or replace it. If it's a fresh restoration, I might chance the stop leak (only because the car has a rubber floor mat)..

Re: Heater core leak
 

Sealers designed for radiators work best under pressure. Your '40 runs zero pounds so the sealer stays in suspension longer and most will simply settle at the lowest spot in the system.
You may get lucky and it may work. It may.
Me? The '40 Fords often ran on the warm side. I'd not do anything that may make that worse.
I'd pull the heater and have a shop solder the leak.

Re: Heater core leak
 

I'm with Kube - the last thing you need is a situation where you plug up your radiator - trying to fix a small leak in the heater core. Pull the core and get it repaired or replaced.

Re: Heater core leak
 

Thank you all for your reply to using Kseal to repair a small leak on a heater core. You convinced me that I need to remove the heater and take the core to a repair shop. The issue of low pressure and the sealant settling before it actually got to the heater core was of concern and Kube, in my opinion nailed the answer Thanks to all.

Re: Heater core leak
 

James, you may be able to solder the repair yourself. Check out the videos on You Tube.

Re: Heater core leak
 

19Fordy makes a good point too. If the leak is easy to access you can do it. I'd use 50/50 solder and the area MUST be clean.

Re: Heater core leak
 

My shop teacher always said whatever you want to solder, needs to be physically and chemically clean.

Re: Heater core leak
 

Muriatic acid can be your friend for cleaning old stuff for soldering.

Re: Heater core leak
 

Slightly of topic but just a note about sealers. I could not find the old go to, Bars Leaks in my local store so I grabbed a alternate of the shelf. It could best be described as 1/4" long thick hairs and the product did stop the rad leak. However when the rad pressure cap did its normal thing by lifting off its seat to drop rad pressure these solid little hairs settled on the seating surface of the rad. As these little guys were quite hard they prevented the cap from sealing to the rad. It was like running without a rad cap, even if the coolant was left low the little guys did their thing. The only way I could get rid of them completely was to pull the rad and the water pumps. As I had thrown the package they came in out I have no idea what the brand name was.

Re: Heater core leak
 

When I bought my '46 Coupe ten years ago, it's general condition was very good. However, being an untrusting soul and longtime mechanic with lots of experience in leaking radiators and heaters, I pulled both and sent them out for cleaning and pressures testing. I also replaced the rad and heater hoses, as they were "baked". It took about fur hours all in, to r&r, refill the coolant and leak check. Better to do a proper fix, than one that may fail in the short term

Re: Heater core leak
 

https://www.fordbarn.com/forum/attac...4&d=1765559356

https://www.fordbarn.com/forum/attac...5&d=1765559356

https://www.fordbarn.com/forum/attac...6&d=1765559356

Re: Heater core leak
 

for my 2 cents do it right do it once sealers are are just a get you home option often the leak is a warning of bigger issuse that you will need to fix later anyway and often with something of that age you find the air side of the core is clogged or corroded and requires cleaning for it to work effectively .Any good rad shop will be able to repair or even replace the core and tanks if its needed and you think its worthwhile when the cold starts to bite