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grannyknot

Repairing a crack in the head

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When we got the engine running the other day I noticed a fairly big oil leak coming from the upper front of the engine, about 1 drop per second, after removing every thing to get a good look I can see a crack that almost circles a flange that holds the front of the head to the timing chain cover. I'm sure this is where the oil leak is coming from.

Behind where the crack is, is the timing chain galley, so what are my options here to fix this? Weld it from the outside, try and seal a patch of some kind over it from the inside? I'm willing to try anything before removing the head.

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I don't see how that can be repaired properly on the car. Needs TIG welding but it will have to be cleaned really well first. You aren't going to get it clean with out a good bit of solvent. You could contact some professional welders or a good machine shop. They might get you a better answer, sorry...I don't see epoxy working either, if the epoxy fails it will be hard to get the epoxy out for clean welding...

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Woof. I don't know what to do about that either. Especially in situ.

Do you think that happened in the accident that resulted in the liberation of the engine?

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Does BMW use the same goofy front cover scheme, with bolts torqued orthogonally on the same general piece of metal?  I was just looking at The L6's front cover bolt arrangement.  If you get the timing cover on the low end of its hole/bolt tolerances you end pulling across a fairly big unsupported gap when you put the top bolts in.

Anyway, I wonder if flushing it with a good solvent, maybe with vacuum behind it, then using some Loctite thread sealer would do it.  Made to wick in to tight spots, fill the gap, stand the heat, not too sensitive to oil, etc.  Easier to burn off than epoxy if you do need to weld.

http://na.henkel-adhesives.com/loctite-industrial-assembly-repair-13281.htm

I think that you could push some epoxy in there also.  Use the bearing packing technique, just keep pressing it in to the gap with your thumb.  Use an epoxy with a long open time.

 

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9 hours ago, Zed Head said:

Does BMW use the same goofy front cover scheme, with bolts torqued orthogonally on the same general piece of metal?  I was just looking at The L6's front cover bolt arrangement.  If you get the timing cover on the low end of its hole/bolt tolerances you end pulling across a fairly big unsupported gap when you put the top bolts in.

Exactly, the small bolt that pulls the head down to the timing cover is not crucial to the seal of the pistons, it's just an oil seal. I was thinking of removing the timing cover, thoroughly clean the area with a variety nasty solvents then apply some kind of flexible sealant like Three Bond 1194 on the inside and outside of the  crack. Then when I go to tighten that bolt wedge a thin shim in the front to take the stress off of the crack. I guess I could even adhere a thin patch of something like pop can aluminum over the crack from the inside. Anyone know what sealant Nissan used in the early valve covers? That stuff is 46 yrs old and has been through thousands of heat cycles soaked in hot oil and is holding up perfectly.

 

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5 hours ago, grannyknot said:

I was thinking of removing the timing cover, thoroughly clean the area with a variety nasty solvents then apply some kind of flexible sealant like Three Bond 1194 on the inside and outside of the  crack. Then when I go to tighten that bolt wedge a thin shim in the front to take the stress off of the crack.

You might find that the piece cracks off if you wiggle it.  Then you could clean it thoroughly and fasten it back where it belongs.  I was going to suggest brazing or soldering before, but thought you were avoiding taking the cover off.  I've seen JB Weld fixes on tougher spots than that though, That would probably be fine.  No real load except the bolt tension.

Looks like somebody might have tried to fix it before by the silicone-looking goop in the seam.

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So I pulled the timing cover to get a better look, it is cracked through to the other side and there is a lip that protrudes above the head surface, although the whole bolt flange is still firmly attached to the head.

I was looking at this stuff, https://www.aluminumrepair.com  

looks like interesting stuff, maybe I should just bite the bullet and pull the head.

 

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 That product looks way cool and you don't have to worry about contamination from the oil. Are you going to cut a shallow v in the crack for better penetration?

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I know the ad says you don't have to clean the piece but I read a few forums where guys had tried the stuff and said all the general rules of solder/brazing still apply, clean everything. I may even stress the flange a bit so I can get some brake cleaner and compressed air in the crack. The real problem with trying to fix it this way is the head itself is a big heat sink and is going to very quickly pull heat out of the area I want to braze. Pulling the head on these engines is quite involved because of cam and shim housing that is bolted to the top of the head. 

I think I'll just stare at it for a few days before I make a decision.

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Got any old aluminum castings?  Crack some and experiment.

I still think a Loctite compound might work easily..  I didn't look through all of their products but wouldn't be surprised if there was a "crack fixer" compound in the list.

I Googled Loctite metal crack repair and http://www.loctite.com.au/metal-filled-compound-4081.htm

Edited by Zed Head

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chris, i have those aluminum brazing rods if you want a go at them.  be warned that it may warp the part or produce a longer crack using the heat required to get it to flow nice, but you're welcome to some if you'd like.

pretty sure they're the exact same ones from the same site. i bought them 5 or 6 years ago when their website was shitty. i used one or two, but it wasn't suitable for my use. I will say that it does produce a surprisingly strong bond to clean aluminum. 

 

 

Correction:

these are the ones i got, Chris:

http://durafix.com/index.html

you're welcome to use them if you'd like. i think they're the same. i have a little stainless brush that's unused too, so you can use that for your repair if need be.

Edited by Careless

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54 minutes ago, Zed Head said:

Got any old aluminum castings?  Crack some and experiment.

I still think a Loctite compound might work easily..  I didn't look through all of their products but wouldn't be surprised if there was a "crack fixer" compound in the list.

I Googled Loctite metal crack repair and http://www.loctite.com.au/metal-filled-compound-4081.htm

i've used similar epoxies designed for this particular use, and i can honestly say that i've never had one that didn't still sweat fluid out from underneath the epoxy. i've used on both iron and aluminum trans cases (as well as magnesium), and also iron/alu cylinder heads with cracked coolant jackets, even engine blocks too. The best of them worked very well for months, and then all of a sudden would develop their own cracks, or worse- the edges would come away/raise from the substrate, and even break off into tiny chips at the ends because its smeared on very thin at those points. 

 

the only time i can say i successfully used an epoxy of that kind for what it was intended was to repair a wollowed keyway on a crankshaft that should still be operating today (i think) and prevented me from replacing the customers motor outright- it wasn't worth it.

I did actually use JB weld one time to restore metal on a gouge that someone created when doing a previous cam seal repair on my old VG30, and all I had to do was smear some on the aluminum gouge with a sliver of an old plastic/credit card, and then hit it with 600 grit paper to smooth it down to accept a new seal, but the seal is what's holding in the fluid in this instance- no sweating of fluid there.

 

Edited by Careless

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Ben, the guy who did the nice custom Tig welding on the modified oil pan has agreed to come down to my place with his potable tig unit and have a go at that crack while the head is still bolted to the block.

I'm thinking this is the safest/best option, it will save me from pulling the head and things won't get much of a chance to heat up until most of the welding is done, then the inside of the crack will be sealed with something, not sure yet. I ground out a small v along the length of the crack with a steel burr cutter, also noticed the crack is getting longer.  Should I drill a small hole at the end of the crack to try and stop it?

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A thought that popped in to my head a day or two ago - drill and tap a hole through the cracked piece in to the meat of the head, countersink the loose end, and pull the crack closed with a small screw.

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1 hour ago, Zed Head said:

A thought that popped in to my head a day or two ago - drill and tap a hole through the cracked piece in to the meat of the head, countersink the loose end, and pull the crack closed with a small screw.

I thought about that too but what about the dissimilar metals heating/expanding at different rates?

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Head bolts, cam tower bolts, front cover bolts, all the same issue.  Steel bolt in aluminum substrate.  Metal stretches and compresses.  It's elastic.  The high end head bolt guys use a stretch calculation for their tightening.  So many degrees of turn equals so much force exerted, based on bolt stretch.

It's just one of many things that might work.  Probably comes down to what operations you're comfortable doing.  The welder likes welding. the chemistry guy likes adhesives, the machinist-type might like the drill and tap idea.

You could probably paint the inside of the head at the crack with glyptal and be fine.  I don't even really know what glyptal is but race engine guys coat the inside of their blocks with it.  Apparently it sticks.  http://www.glyptal.com/

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I believe Glyptal is a high end coating that was originally used in electrical transformers. Racers like to use it in their blocks to seal the casting so no loose grit can shed into the oil and it enhances oil drain back to the sump. At least that is the way I remember it. I researched it once for a motor rebuild but never used it...

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12 hours ago, grannyknot said:

Should I drill a small hole at the end of the crack to try and stop it?

That's the accepted way of stopping crack growth.  Because you're going to have the crack welded, though, doing this might be either: a. even more important (large thermal stressing), or; b. not necessary (welding solves the issue).  You won't know the correct answer until after the heat hits it.  Because of the fear that the correct answer may be 'a', a compromise solution might be to drill a hole to half depth.  Looks like a 3/16" bit would be about right. 

If your welder buddy has a lot of experience with aluminum casting repairs, he should be able to offer a better opinion.

 

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