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Tonyz2897 06-11-2012 08:02 AM

Aluminum block, cracked deck.
Hi everybody!
I've got an LS1 with a small crack starting at a water jacket and stopping at the #8 sleeve. The sleeve itself doesn't appear to be cracked. The engine runs fine and isn't ingesting any coolant but it is pushing a small amount of combustion gasses back into the cooling system.

I'm wondering if there are any in-car tricks I could try to get it to seal up completely? I've had a couple ideas so far, one involving low-temp aluminum "brazing rod" and then working the repair down flush with the deck surface with a flat file. The other was to try some X-Seal Acrylic 120 which is a penetrating acrylic sealant used for sealing porosity and cracks in castings and then throwing on a new gasket with a layer of copper spray.
Either of these sound like they would work or am I just wasting time/money?

The last time I had the head off, It sealed completely just from the fire ring of a new gasket but it only lasted about 2 weeks before it started pushing combustion gasses again. That leads me to believe that if I can do something about the crack, I should be able to get it to seal permanently (or at least long enough to build a new bottom end).

Any tips, tricks, or advice would be appreciated!


DoubleVision 06-11-2012 09:12 AM

Aluminum blocks can easily be welded and refinished. Yeah you'll have to remove it and strip it all the way down but it's going to be the only way you're going to stop it for good. When you torque down on the head bolts it desorts the deck, especially where the crack is which usually causes the band aide to give up.

Tonyz2897 06-11-2012 09:44 AM

You don't think a repair with an aluminum "brazing" rod would hold? The package claims they have a 40,000 psi tensile strength. I'm thinking notch the crack slightly with a small carbide burr, braze it, and then carefully work the repair down to flush with the rest of the deck surface using a flat file and checking with a straight edge.


OneMoreTime 06-11-2012 12:29 PM

I have done some weird things so what you propose just might be worth a try..Of course the right way is to have it welded and surfaced but then sometimes we have to do the not recommended way to "git er done" :pimp:


Tonyz2897 06-11-2012 01:23 PM

That's kind of where I'm at right now. I'd like to fix it right but can't afford to have it down for much longer than a weekend at a time. Eventual plans are to bolt all the LS1 goodies on a 6 liter iron block but I'd like to try to keep it going until I can build a nice bottom end rather than toss in a junkyard long block in a hurry out of necessity.


1BAD80 06-11-2012 02:39 PM

If you fixed it before the right way you would not be asking for a band-aid fix now. If you have compression in the coolant system now, it's bad, it can go on you any time, like blow the radiator, heat up and freeze the motor then how much would it cost you with towing or steam up the windshield while your driving, your wipers won't help either and be SOL .
Fix it like DV said before something happens.

Tonyz2897 06-11-2012 03:56 PM


Originally Posted by 1BAD80
If you fixed it before the right way you would not be asking for a band-aid fix now. If you have compression in the coolant system now, it's bad, it can go on you any time, like blow the radiator, heat up and freeze the motor then how much would it cost you with towing or steam up the windshield while your driving, your wipers won't help either and be SOL .
Fix it like DV said before something happens.

Seriously? All that over pushing a small bubble or two into the cooling system every 20 seconds or so from a hairline crack? Like it's been doing for the roughly 6 months I've owned and daily driven the car (with the exception of the two weeks after the new gasket)? And now it's all of a sudden going to overheat and seize or explode the radiator? Sorry dude, I'm not buying into all the gloom and doom nonsense. As far as I'm concerned the bottom end is already junk and you're right, I am looking for ideas for a band-aid. All it needs to do is seal up and stay together long enough for me to scrape up the extra cash to put together a new short block.


S10 Racer 06-11-2012 05:37 PM

I'm a "home brew" type hillbilly. I think even if you remove the head and weld the crack, you still run the chance of it leaking because unless you get 100% penetration, when you torque the head, you run the chance of the crack re-appearing.
If you only want a temporary fix for say a year or so, I would buy some liquid sodium silicate grades 40 and 42 (waterglass). This stuff has been used to seal engine issues for many moons (along with other things). I use to buy it at the local pharmacy. I would stay away from the similar stuff you can buy at Wal-Mart. You will need about 1 quart of waterglass. The best way to treat your system with it is to drain the cooling system. Disconnect your heater hoses as the waterglass may clog up your heater core. Fill the system with clean water. Start the engine and bring up to operating temperature. When the temperature is say 180-190, add the waterglass to the radiator and replace the cap. Let it idle for 1-2 hours and then drive it around for about 30 minutes, park it and let cool enough so you can safely drain the system again. Drain the system again and fill with the proper antifreeze/water ratio. Reconnect the heater hoses and you're done.

If your cooling system is fairly clean, you can just drain about a quart of coolant, start the engine and let it get warm and add the waterglass to the anti freeze and just leave it in the system. I believe that some anti freeze manufacturers use sodium silicate in the manufacturing process.

ssmonty 06-11-2012 05:47 PM

2 Attachment(s)
I had an aluminum intake welded up a little, and it needed some work get rid of some high spots.
I thought that I could do it with a file if I was real care full. I'm usually pretty good at stuff that takes a steady hand, and a little fineness, and working with hand tools. Totally botched it IMO. Left scratches deep enough that I thought it might cause leaks(extremely easy to do on aluminum). I went ahead and took it to work were I have access to a mill, and shaved about .005" off and cleaned it up.
I think the guys are aware, and trying to tell you that it would be extremely difficult for you to make the repair with a hand file on a critical block sealing surface, especially when its in the car, and that you would do more damage than good. If there not, I am.
Good luck,

1BAD80 06-11-2012 06:29 PM

Seriously? then go out and get a bottle of Bars Leak thats no brainer.

FmrStrtracer 06-11-2012 11:29 PM

Yes, you can repair it like you mentioned.

Will it hold?

Cant say until you drive it.
If you believe in the quality of your work, give it a go.

I'd add a can Bars leak super strength head and gasket repair, for some extra insurance, and,

Get workin on that 6.0

S10 Racer 06-12-2012 10:34 AM

Personally I have had little luck with Bars Leak in numerous systems. It also makes the system brown in color because it's a dark color. My favorite is water glass because it's clear or the silver powder type sealer. Both of these work good. Just my .02

Tonyz2897 06-12-2012 12:52 PM

Thanks for the suggestions everybody. I'm afraid any of the products that mix with the coolant are never going to be exposed to the crack because of the way it's leaking. As far as I can tell, no antifreeze is making it into the cylinder in question. No steam cleaning effect in the combustion chamber or piston crown and no excessive steaming from the exhaust. I'm under the impression that the crack or the intact fire ring between the end of the crack and the cylinder is causing a "one way valve" effect where coolant can't leak in but a small amount of the higher pressure combustion gasses are able to push past into the cooling system. That said, I did put some Bars in it right after it started acting up again but without much hope that it would help.


FmrStrtracer 06-12-2012 03:59 PM

You have to use the newer Bars Leak that is designed specifically for aluminum heads and blocks. Not the original brown stuff with the rabbit turds in it.

Tonyz2897 06-17-2012 01:51 PM

I'm assuming this was the newer stuff. Gray bottle that claimed to be compatible with all types of coolant...

I think I may be on the right path to a permanent solution. A friend called this morning after having run across a 6 liter from an early '00s 2500hd. The engine runs but needs freshened up. He's currently waiting on a call back from the owner with regard to price. If this deal comes together, I'll freshen up the 6.0 short block, bolt on the ls1 heads, manifold, and accessories, and drop it in the car. That'll also give me a chance to settle on a cam/converter combo and do both at the same time. I should be physically and financially able to have the new engine ready to go in by the end of summer. For now I'm just going to drive it as-is, keep an eye on the coolant level and temp gauge, and hope for the best.


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