The Stovebolt Site Forums The Shop Area Engine Shop Sodium Silicate/Liquid Glass

Anybody had any good results using sodium silicate to fix a cracked block? The internet is a mixed bag of pros and cons. Some say it works great and others not so much...plugged radiators, heater cores, short duration before leak comes back, etc. My 270 block has a 6 inch crack. Tried Marine Tex but part of the crack is starting to leak so may try grinding away the old epoxy and see if I can get a better bond. Any other ideas other than find a good block?

Waterglass (oldtimers' name for sodium Silicate) only works if the crack is exposed to combustion heat. The heating cures it to, literally, glass, with a melting point of 900+ degrees. When the 503 cubic inch GMC in Ed Pruss' retired fire truck had a seep leak at the head gasket, I flushed the system several times and added sodium silicate, and drove it from middle Tennessee to Kansas City. Ed picked it up there and drove it on to Denver. After about a year, it started leaking again and he had a terrible time getting the glued-down head off the engine. It's a temporary fix at best, but a pretty good one- - - -as long as the leak is internal. The only way to fix an external crack is to weld or braze it, or possibly to use overlapping cast iron threaded tapered plugs- - - -a process called "sewing" a block. The plugs and the tooling to install them is expensive- - - -let a machine shop that's already set up for the process do it, and be glad you don't have to buy a tap, a taper reamer, and a minimum purchase of a hundred plugs.
Jerry

I used it once on a 235 that had frozen and had a seeping crack in the water jacket on the side of the block. It worked fine for me. The best place to get the good stuff is at a pharmacy. It cost next to nothing.

Jerry spells it out-it must be exposed to combustion heat, temporary only-antifreeze may hasten it's demise. You don't say where the crack Is? There are 270 and 302 blocks around.

Ed

Thanks for the input. The crack is on the left side of the block, some off center towards the rear and about 4" above the pan flange. Everything I read about water glass didn't mention the need for hi heat to cure, so that eliminates sodium sil, which I was pretty decided on anyway. I've located a 248 engine as a backup and still have my old 228 crank, rods and pistons if I can't find a good 270 block. The machine shop that did the work on the 228 has done the metal repair on another job, so he may still have the tooling if Lock and Stitch will sell the screws otherwise there is probably a machine shop around that can do the job. Another potential problem is whether they can do it with the engine in the truck without removing the left inner and outer fenders and manifolds. Just more fun.

Bill

Don't even think about an in-place repair. The block needs to be cleaned, stripped down to bare bones, and on a stand where the crack can be repaired properly. It sounds like your best option would be another layer of Marine-Tex, or just ignore the seep and check the coolant level in the radiator once a week- - - - -what's a few drops of coolant leakage to the outside going to hurt in the first place?
Jerry

I have had good luck with Marine-Tex on external cracks if I prepared the cracked area properly. First sand or media blast to grey metal, warm along crack to extract any moisture, make a shallow "V" in crack with a Dremel tool, rough up the surface with a 24 or 36 disc on an angle grinder to an inch or so on each side of the crack, apply the Marine-Tex no more than 1/8" thick over entire prepared area. Picture is a 40 Pontiac block done in 2010 that is still holding fine. The crack has been warmed to drive off moisture.

[img]https://s1.postimg.org/1k8ao9btln/1940_Pontiac_Cpe_004.jpg[/img]

As the patch is curing, press a piece of 40 grit sandpaper over it, then remove it gently- - - -the texture of the sandpaper matches the surface finish of cast iron almost exactly.
Jerry