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Machine Shop and Tool Talk

Plugging tiny cracks in aluminum


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  #1  
Old 12-05-2008, 03:05:01 AM
Beanscoot Beanscoot is offline
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Default Plugging tiny cracks in aluminum

This is on a modern car, which has a water cooled aluminum head. This head was badly cracked so I had it welded up somewhat successfully, but there remain a couple of tiny cracks in the intake and exhaust ports, and they presumably extend into the water jacket.
The welder recommends against further welding as it seems to be chasing cracks around. So while the head is off and clean, I am trying to find a good compound to stuff into the cracks to seal them. Epoxy would be good, but it's too viscous to get in well. I think crazy glue or Loctite might not harden.

Any ideas? I'm also thinking of hooking up a vacuum cleaner to the water passages and help suck in whatever glue I use.

Thanks for the help.
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Old 12-05-2008, 07:13:37 AM
John Schwiebert John Schwiebert is offline
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Default Re: Plugging tiny cracks in aluminum

I am grinning while I read this> when I worked for my other employer we worked with a guy that had a patent on the welding of cracked aluminum heads. He also had a patent on a process that once the head was welded that in a sense ran this "liquid" through to coat the internal passages in the head. Several things were not mentioned. Has the head been pressure tested? Can you get at the cracks? We did a pair of big block (aftermarket) aluminum heads thad had suffered mechanical damage. and we found about a handfull of small pin holes. We put Irontite aluminum plugs in those small holes. The same thing will also happen if you try to stick weld old cast iron heads without the proper procedures. You will find pin holes that develop in a sense inches away from the crack. Now has the head been restraightened and or re-machined since it has been welded?
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Old 12-05-2008, 01:42:41 PM
KHill KHill is offline
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Default Re: Plugging tiny cracks in aluminum

When I owned a foundry we used to impregnate castings to seal micro cracks and pin holes in pressure tested castings.
You can go to www.saranindustries.com and get an idea of what I am talking about.
Keith
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Old 12-05-2008, 02:12:31 PM
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CaseyJoeS. CaseyJoeS. is offline
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Default Re: Plugging tiny cracks in aluminum

I belive brazing aluminum in some way is possible if you have the correct rods and flux?
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Old 12-05-2008, 02:43:01 PM
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Forrest A Forrest A is offline
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Default Re: Plugging tiny cracks in aluminum

You may have to re-machine the mating surfaces if there was uneven heat applied to the AL casting due to warping. Also, you need to use something that will not be attacked by Gas or ethanol (and any other additives). I don't know of too many positive results from trying to repair a broken AL head...

Forrest A.
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Old 12-05-2008, 08:01:34 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Plugging tiny cracks in aluminum

Cadillac recomended Bars Leaks radiator stop leak in their aluminum blocks to stop leaks through porous castings.
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Old 12-05-2008, 09:43:05 PM
gpkull gpkull is offline
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Default Re: Plugging tiny cracks in aluminum

"blue devil" money back if it doesnt do the trick. you must follow step by step. has worked for me. you have to be loosing a lot of water quickly for this not to work.
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Old 12-05-2008, 11:26:48 PM
Beanscoot Beanscoot is offline
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Default Re: Plugging tiny cracks in aluminum

Thanks for the replies. I might try to get some of the special Loctite Resinol RTC mentioned in the Saran Industries site.
Although this head is newish, (1995) it has all the fun of an old engine... A head bolt broke off when taking it apart, resulting in the head being firmly stuck to the block due to the remainder of the bolt firmly rusted into the head. I had to use thin steel wedges on each end stuck into the head gasket area, while also stuffing one cylinder with thin rope through the plug hole, and spinning the engine to cause the piston to pound the mass of rope into the head. After hours of fooling around like this I finally got it off.

The head of course has a little damage from the wedges, and the marks of its previous belt sanding were evident on the gasket surface. Then the bad cracks were welded up, so it will be resurfaced after the rest of the work is done. It will have four new valve seats (the old ones needed to come out to allow for the welding), as well as eight new guides, due to sitting too long in a phosphoric acid (aluminum cleaner) tank.

Yes this is a ridiculous amount of work for a disposable head, but hey, you've got to have a hobby!
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Old 12-06-2008, 01:00:31 AM
terry tabb
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Default Re: Plugging tiny cracks in aluminum

gasket eliminator , turns almost like glass,lock tight, there something else you can use but it your last thing you want to use it called water glass, if this is a pontiac vortac engine just get another head ,what engine are you doing all this on, model car is it , 1995 what, water glass has a weird smell to it when its in the engine , it well work for sometime but then fell fast, if you smell something weird like that ,dont by that car, used car dealers tricks, yeap i bought one and lasted just long enough to get about a month and then water out the exsust,not good talk to joe at the auction house and he told me that it had water glass in it, works on small cracks you got that much in it you could try it,
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Old 12-06-2008, 04:01:07 PM
Beanscoot Beanscoot is offline
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Default Re: Plugging tiny cracks in aluminum

1995 Escort 1.9 Liter.
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