Head Temperature Boss Crack

[100550dvr]

I am restoring a 1950 Canadian F47 Truck. The engine was completely overhauled by a builder in the Twin Cities. Adding coolant to the system for the initial start, we discovered a crack in the head temperature sender boss area. Photographs attached. Never noticed this crack before. The plug depicted was installed during overhaul. The builder said to add some stop leak. I've always considered stop leak products to be a temporary fix. Am I wrong? Will a good stop leak material address this problem? Any better brand than others? I would prefer to remove the head and grind/weld the crack. Am I only chasing the problem? Will I create more problems?


Any ideas or proven solution would be most welcomed. Obviously, I am not happy about this.

[rich b]

Does not look like a good application for stop leak; replace the head.

[rotorwrench]

Coolant leaks when you are getting ready to run are always a nightmare. The nature of a National Pipe Thread joint just makes it worse. A coolant sealer additive like Bar's Leaks might work but on a person hates to put stuff like that in a new engine or with a new radiator. I'd pull the head and replace it if it were mine. If it was a special head I might want to try and repair it but if it is a common one then it would go in the boat anchor box.

[papanomad]

I had same crack on a 59ab head and used high heat jb weld to repair. grind a v in crack and fill with jb weld. that was 3 years ago and still holding.

[flatjack9]

Just do not overtighten the plug. Use a good pipe thread sealant.

[dumb person]

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1.5 mm drill bit at the end of the crack and some epoxy, i've seen people use solder but that's for diehards.

[100550dvr]

Canadian heads have the words MADE IN CANADA in raised letters on the head. That's why I would like to keep it.

[Karl Wolf]

Originally Posted by flatjack9

Just do not overtighten the plug. Use a good pipe thread sealant.

X2,
I would get a 3/8" pipe tap and run it in a ways, so as to set the plug in deeper.
Use penetrating locktite on the crack. Give that some time. Put the pipe plug back with sealer (Three Bond would work) in just tight enough so it won't rattle out.

I would be curious to address the person who installed the plug -causing the crack.

Karl

[flatheadmurre]

There´s a product called fluid-weld from seal-lock that is made for this kind of issues...
A machine shop doing crack repair should have it around...
2oz cost somewhere in the $30 range.

[Jack E/NJ]

rotorwrench>>>Coolant leaks when you are getting ready to run are always a nightmare. The nature of a National Pipe Thread joint just makes it worse.>>>

Nah. A nightmare happens when its a fuel leak from a cracked FPT connection. Jack E/NJ

[JSeery]

As stated above, drill the end of the crack to stop progression, tap the hole deeper and use a sealant when installing the plug. Do not crank it down that tight when it is reinstalled. If you are interested in using a water system sealant consider water glass.

[flatford8]

X3 on post #5. Are you running temp gauges?.....Mark

[marko39]

i have the same crack in my 8BA head found when i pressure tested. this was caused by over tight plug. i removed plug and used Permatex non hardening sealer on threads. leak stopped. just tighten plug until leak stops as the more you go the more the crack opens. Mark

[rotorwrench]

Originally Posted by Jack E/NJ

rotorwrench>>>Coolant leaks when you are getting ready to run are always a nightmare. The nature of a National Pipe Thread joint just makes it worse.>>>

Nah. A nightmare happens when its a fuel leak from a cracked FPT connection. Jack E/NJ

I don't think you have ever had coolant come out of a exhaust port when your filling it for the first time after overhaul.

I'd just bolt the head to an old block and braze the crack up if I wanted to repair it. Check it for head sealing surface warpage after & put it back in service if good.

[D. Jones]

If it were me I'd drill the end to stop further cracking, clean it and solder it with "Brownell's High Force 44 low temp solder" and then carefully re-tap to clean the threads and replace the temp sender using a good thread sealer. The High Force 44 flows at about 475 deg's F and is rated at 28,000 psi strength, much lower temp than brazing so less chance of warping.


Just my $0.02 worth.

[russcc]

Some great ideas. I like the Fluid Weld product. The machine shop that did the 59L used it when they installed the valve seats in the event there was any chance of coolant leakage. They also used it on a porous block they bored and sleeved.