Weld a hair line crack in a Cast Iron Rad?

GW

So, I forgot you can crank on the 1/8" plugs; i was testing out the rad with water pressure and tightened the old steam air vent too much and put a small crack in the tube.

Must i ditch the rad or is it safe to weld in a black 1/8" plug and be done with it? My local auto mechanic says he would rather not because he's afraid the weld will not expand/contract at the same rate the CI will.

Thanks for any help

gary

ALH_4

Crack

How about brazing?

Brad White

This is a job for JB Weld.....

Cast iron is a bear to weld because of the granular structure. Brazing has been done with some success but this is an art. I imagine if low pressure steam, if the JB Weld holds to temperature (it can patch engine blocks) it is your best bet.

Worst case is you replace the section. If not that, then the radiator. Try JB Weld first according to directions, test and see. Good luck~

Brad

GW

JB

Brad, I'll grab some at the hardware store. have you any idea how much pressure this can hold? i will certainly be running at normal pressures when it's installed but would love to test at 30 to 40 of so. Think I'm good?? rather not comment?? Thanks!

Mike T., Swampeast MO

I'll second the JB Weld for hairline cracks. Works very well. Clean the area very well--wire brush or similar as well as a solvent like naptha.

I test with house water pressure--about 65 psi here. Have a number of rads repaired with JB Weld in use in my house for about 10 heating seasons and never a problem. Only time the JB Weld hasn't worked for me is with column type rads when the crack was along a sharply angled distinct corner of the casting.

I've watched people attempt to braze crack in cast iron--the cracks just run like crazy. Supposedly it will work better if you drill a little "relief" hole at the very end(s) of the crack(s).

Brad White

From the inside....

The only thing I can add to that, Gary, is to apply it from the inside such that any pressure would force the material into the crack rather than out of it... But then, I am not sure how well you can prep the back side of the crack except by degreasing solvents as Mike T. mentioned.

The material you buy, Grasshoppa. The skills, those are yours. Go forth...

Jack

For those with experince

Would you not want to take a dremel and open up the crack a bit and maybe preheat the area a bit too. You do not call some one who can weld cast iron a welder. Yu call them an artist! I made a living as a welder and I could never do a decent job on anything cast iron.

Mike T., Swampeast MO

On the flat or rounded surfaces, I just smeared the J.B. Weld on the outside with my finger--maybe 1/16" thick and feathered out the edges. Probably about 1/2" wide overall. These were hairline cracks that would mainly just ooze water during a pressure test.

Tom Hopkins

Welding cast iron

Yep, it is an art. If you torch weld a crack in cast with brazing or cast rod you're sure to create a stress crack nearby due to uneven expansion from heat. The old timer at a welding shop in a past life would build a charcoal fire and heat up the whole piece. Yeah, I was the teenager with the bellows. I don't know how he knew when the entire piece was hot enough to throw some oxy-acetylene at the ground out crack and braze or weld with (yes) cast iron brazing rod, but by the next morning, when all had cooled evenly, the crack was welded with no peripheral cracking. Yep, it's an art.

That being said, JB weld or two part epoxy is the answer. I would certainly grind out the crack with a dremel or die grinder to good clean metal. Clean with laquer thinner. If it's structural (not in this case)drill a couple of pins into the cast to hold the attached piece.

Nothing is impossible!