Welding Tips and Tricks

Hey guys, I’m new to welding and especially trying to learn Tig welding more than anything. Some backstory to my question here. Audi s4 threw a belt and broke off a little chunk of aluminum which was a protrusion for a bolt and caused a 3” hairline crack in my block, now it’s leaking oil. My question is what type of filler rod can I use for cast aluminum? I’ve read somewhere that 4043 can do it which I assume is the most basic/popular rod. Also I think I can get to both sides of the crack, from the outside and inside the crankcase. How should I weld it so it doesn’t crack again. Should I grind out a “valley” in the crack and fill it up or can I just weld right on top of it? I bought a new Everlast mts 225 to be able to weld it. Lol it was kinda an excuse. And of course I will practice more before welding it.


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Maxdub wrote:Hey guys, I’m new to welding and especially trying to learn Tig welding more than anything. Some backstory to my question here. Audi s4 threw a belt and broke off a little chunk of aluminum which was a protrusion for a bolt and caused a 3” hairline crack in my block, now it’s leaking oil. My question is what type of filler rod can I use for cast aluminum? I’ve read somewhere that 4043 can do it which I assume is the most basic/popular rod. Also I think I can get to both sides of the crack, from the outside and inside the crankcase. How should I weld it so it doesn’t crack again. Should I grind out a “valley” in the crack and fill it up or can I just weld right on top of it? I bought a new Everlast mts 225 to be able to weld it. Lol it was kinda an excuse. And of course I will practice more before welding it.


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Not trying to be smart, but best filler rod to use is E-autoinsurance. Got full coverage?

Lol no. It’s a 2006 and not a regular family car. It’s a “car guys” car.


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I'm not a tig guru, so I want to preface that.

There are a couple things to consider.

4043 has silicon in it.

4643 also has silicon, but it has a small amount of magnesium, and my understanding is this makes it a tad stronger than 4043, and many people like to use this.

5356 has magnesium in it. This is much stronger and is also used by people that anodize as you can anodize it. It is also more ductile from what I have read.

On the surface you would think 5356 would be the best filler to use, it's the strongest and allows for anodizing. But I think it depends on what your application is because the magnesium doesn't stand up to heat as well, so one of the 4000 series fillers could be a better choice for certain high heat applications like a radiator, I've heard.

No matter what you choose, you should definitely grind out a valley and clean it really well down to metal. Engine parts are notorious for oil in and around the parts, even inside that crack, IMO, you need to get all the way through the crack into clean metal.

Mark Winchester is an amazing aluminum tig welder who builds valve covers and he uses 5356 primarily. Valve covers do get hot, but he does it in case someone wants to anodize their covers, so he says. He was on WTAT podcast this week.

That said, I can't really tell you what is best for your application as I'm not new to tig, but certainly not a seasoned virtuoso, but the above is stuff you should consider. I have never done such a repair, but there are folks here who have so take their advice. I think BugHunter has worked on engines quiet a bit, and I would/do take advice from cj, Poland and LtBadd.

Maxdub wrote:Lol no. It’s a 2006 and not a regular family car. It’s a “car guys” car.


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I hear ya. Is the engine block already out of the car and disassembled? I couldn't imagine trying to work on it with it in-car.

Lots of repairs are demonstrated on YouTube using 4043, but even then I think 4943 would be a better choice if it were me.

Oscar wrote:

Maxdub wrote:Lol no. It’s a 2006 and not a regular family car. It’s a “car guys” car.


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I hear ya. Is the engine block already out of the car and disassembled? I couldn't imagine trying to work on it with it in-car.

Lots of repairs are demonstrated on YouTube using 4043, but even then I think 4943 would be a better choice if it were me.

No. Engine is inside. The crack is at the front and really low, just above the oil pan so all I needed to do was remove the whole front end/radiators. I did have the engine out before, I was doing a timing chain service and if anyone’s worked on German cars you know what they like to do. It’s super tight everywhere and a pita to pull the engine. Plus it’s not really necessary, plenty of room to weld.


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TraditionalToolworks wrote:I'm not a tig guru, so I want to preface that.

There are a couple things to consider.

4043 has silicon in it.

4643 also has silicon, but it has a small amount of magnesium, and my understanding is this makes it a tad stronger than 4043, and many people like to use this.

5356 has magnesium in it. This is much stronger and is also used by people that anodize as you can anodize it. It is also more ductile from what I have read.

On the surface you would think 5356 would be the best filler to use, it's the strongest and allows for anodizing. But I think it depends on what your application is because the magnesium doesn't stand up to heat as well, so one of the 4000 series fillers could be a better choice for certain high heat applications like a radiator, I've heard.

No matter what you choose, you should definitely grind out a valley and clean it really well down to metal. Engine parts are notorious for oil in and around the parts, even inside that crack, IMO, you need to get all the way through the crack into clean metal.

Mark Winchester is an amazing aluminum tig welder who builds valve covers and he uses 5356 primarily. Valve covers do get hot, but he does it in case someone wants to anodize their covers, so he says. He was on WTAT podcast this week.

That said, I can't really tell you what is best for your application as I'm not new to tig, but certainly not a seasoned virtuoso, but the above is stuff you should consider. I have never done such a repair, but there are folks here who have so take their advice. I think BugHunter has worked on engines quiet a bit, and I would/do take advice from cj, Poland and LtBadd.

Thanks for the tips. And should I also stop drill it or is it not going to make a difference?


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Here’s some photos of how much room I got and what the crack is. As well as the small chunk of aluminum that broke off.


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Maxdub wrote:Thanks for the tips. And should I also stop drill it or is it not going to make a difference?

Absolutely, if possible, any crack should be stop drilled.

It really depends on where it is and if you can or not. If you can't get access with a drill, at minimum you should use a carbide burr to grind it all clean, and past the ends as well to get to clean metal. If you can stop drill in clean metal and have access, by all means do it, IMO.

In looking at the photo you just posted, I would be careful whatever you do, no telling where baffles or channels wind through there. I would try to stop drill from the left side, into the shoulder if you can get to clean metal there, check the crack. And then grind it all out cleanly, you have quite a bit of material to work with, but I'm not sure if that's got a cavity behind that area or not, so I would caution on going too deep in case. A parts diagram may help to give you an idea what is behind there.

Wait a sec, looks like the crack goes through the first shoulder and into the 2nd, looking at it closer. You'll need to clean all of that out so not sure you can easily stop drill it, but you need to clean the entire crack out if possible.

Maxdub wrote:Hey guys, I’m new to welding and especially trying to learn Tig welding more than anything. Some backstory to my question here. Audi s4 threw a belt and broke off a little chunk of aluminum which was a protrusion for a bolt and caused a 3” hairline crack in my block, now it’s leaking oil. My question is what type of filler rod can I use for cast aluminum? I’ve read somewhere that 4043 can do it which I assume is the most basic/popular rod. Also I think I can get to both sides of the crack, from the outside and inside the crankcase. How should I weld it so it doesn’t crack again. Should I grind out a “valley” in the crack and fill it up or can I just weld right on top of it? I bought a new Everlast mts 225 to be able to weld it. Lol it was kinda an excuse. And of course I will practice more before welding it.


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its not really a beginners project. its one of the harder things to weld.

your going to have to grind that crack out so you can weld right into it.
you will also have to deal with the oil thats soaked into it, which is usually a nitemare.
plus if its broken off a bolt mount, you need to get that back in the right place.

if you can't take that bit off the engine, your going to have to drop the oil pan, clean out the block (any left over oil is going to catch on fire). plus remove anything plastic or heat sensitive as your probably going to get in there with a gas torch to cook out the oil.

Maxdub wrote:
Here’s some photos of how much room I got and what the crack is. As well as the small chunk of aluminum that broke off.


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that crack goes to the coolant channel as well. thats going to be interesting as you will have to fill it in then machine the o ring groove. also have to check that the crack hasn't gone all the way into the coolant channel. otherwise you risk the crack opening up when hot. you might have to groove all the way into that coolant passage.

you can fit the bolt from the bottom and weld around it. the bolt that comes in from the front you will probably have to fill in then drill and tap after. there is a fair few hours of welding building that chunk back up.

filler, 4043. 5356 won't like the heat of the engine.

I’m definitely going to take the oil pan off to see whats behind and what’s what. And that’s a coolant passage way to the left and the crack migrated there, as to why I was hoping to weld from the inside. And I might even be able to remove the upper oil pan if it’s not to much work or even just replace it if I buy one for cheap. The bolt mount doesn’t hold anything serious, just a snub mount to support the radiators. If I see that I won’t be able to do it, as you said it’s not really a beginners project, I will hire someone that can. I’m not really keen on “welding” a hole in my engine.[emoji38][emoji32]

tweake wrote:

Maxdub wrote:
Here’s some photos of how much room I got and what the crack is. As well as the small chunk of aluminum that broke off.


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that crack goes to the coolant channel as well. thats going to be interesting as you will have to fill it in then machine the o ring groove. also have to check that the crack hasn't gone all the way into the coolant channel. otherwise you risk the crack opening up when hot. you might have to groove all the way into that coolant passage.

you can fit the bolt from the bottom and weld around it. the bolt that comes in from the front you will probably have to fill in then drill and tap after. there is a fair few hours of welding building that chunk back up.

filler, 4043. 5356 won't like the heat of the engine.

tweake wrote:

Maxdub wrote:
Here’s some photos of how much room I got and what the crack is. As well as the small chunk of aluminum that broke off.


Sent from my iPhone using Tapatalk

that crack goes to the coolant channel as well. thats going to be interesting as you will have to fill it in then machine the o ring groove. also have to check that the crack hasn't gone all the way into the coolant channel. otherwise you risk the crack opening up when hot. you might have to groove all the way into that coolant passage.

you can fit the bolt from the bottom and weld around it. the bolt that comes in from the front you will probably have to fill in then drill and tap after. there is a fair few hours of welding building that chunk back up.

filler, 4043. 5356 won't like the heat of the engine.

I have the chunk that broke off. I can just weld it back on, right? So 4043 or 4943 as someone mentioned? This one guy told me I would need nickel laced rods something about softening the base metal? Should I disregard that?



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You need to clean that really well, not just so-so, but really well if you want to weld it.

I have to agree with tweake, it's not a beginner task, but I've never let that stop me in the past...

It looks like it will line up pretty well, if you can get it all welded and run a tap into the threads it might clean them up if they're a tad off, but I would take your time when you weld it. You'll probably need to run a tap through the side and bottom threaded holes.

Can you get that out of the car? That will make it slightly easier to burn the oil off and get it cleaned and ground before you weld it. Worst case you ruin it and need to get another replacement part, but it looks like it's toast if you don't try and/or replace, so it seems you don't have too much to loose by trying...my $0.02...

Your other option is duct tape...

Yea that would take me a whole day to clean it up to the point that I would be comfortable TIG welding it. That machine lip will take a lot of careful work to get back into shape after welding into it (since the crack extends into it). Exhaust port? Good thing this is a "play car" and not your daily-driver.

Please go to a scrap yard and get a busted up aluminum cylinder head from ANYTHING so you can learn to dial in your settings. It will likely take every ounce of juice from that welder to make that engine block puddle quickly. I don't know if that everlast model has their hybrid AC waveshape that pulses DCEN, but if it does, it will likely help tremendously. A good 150°-200°F pre-heat might also help, but of course this is where you would practice on a junk head first.

Maxdub wrote:This one guy told me I would need nickel laced rods something about hardening the base metal? Should I disregard that?

Yes, I think you should ignore that. Nickel rods are for repairing cast-iron parts, not aluminum.

To really determine the correct filler, you need to know which alloy of aluminum was used for the casting. If Audi won't tell you what it is, you can have a lab analysis done. MONEY
That area will have to be cleaned inside and out, to an almost surgical level. Then you can use Zyglo (best), or another dye penatrant process to determine the extant of the cracking. MORE MONEY
The welder doing the repair, will need a level of experience and knowledge about equal to that of a leading heart surgeon.

To do it right, could easily approach the cost of a new block.

No way would I weld on that block still in the car. Computers, and some sensors, can be bricked by such action. The amount of heat required to fix the block could warp it. On some German aluminum engines, the block or crankshaft are not available as separate parts. The clearances are so critical on the bearings, that there is no service info for the crankshaft. The only option they offer is a replacement short block.
If it were mine, I might try to bodge it with 4943 just to see. I would keep enough money in the bank, for a replacement engine.

Maxdub wrote:I have the chunk that broke off. I can just weld it back on, right? So 4043 or 4943 as someone mentioned? This one guy told me I would need nickel laced rods something about hardening the base metal? Should I disregard that?



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nickle rods is for cast iron not cast aluminium.

not sure with 4943 and its only made by one or a few companies anyway.
4043 is available anywhere.

i doubt you could weld it back on. considering bolt size it must take a bit of load. i'm not sure if welding around the outside would be strong enough. grinding back in is going to remove a lot of the chunk anyway. also you would need to clamp it in place with the bolts in it.
my understanding is you can't just melt an aluminium crack, or two faces to fuse it, because of the layer of oxide on each face in there. the oxide doesn't melt, causes porosity and becomes a place where a crack will start. (would love some other opinions on that).
to get rid of the oxide need to get in their with the ac arc.

i would check out @tighappens on instagram as he does quite a bit of this type of work (and its awesome!).

tweake wrote:i doubt you could weld it back on. considering bolt size it must take a bit of load. i'm not sure if welding around the outside would be strong enough. grinding back in is going to remove a lot of the chunk anyway. also you would need to clamp it in place with the bolts in it.
my understanding is you can't just melt an aluminium crack, or two faces to fuse it, because of the layer of oxide on each face in there. the oxide doesn't melt, causes porosity and becomes a place where a crack will start. (would love some other opinions on that).
to get rid of the oxide need to get in their with the ac arc.

I agree, a repair like this, done properly (but without the metal analysis part) would take me (if I were to ever attempt one), at least 3-5 days when you add up all the nickels-n-dimes, meaning ALL the little time-consuming details that need to be thought out thoroughly. Dye penetrant is definitely a good idea. The stop-drilling would be the trickiest part IMO.

Most of the good repair I've seen on YouTube by seemingly experienced fab shops use a die grinder with a carbide burr to really fish out all the dirty aluminum/oxides and find very clean metal underneath, while simultaneously creating a V-groove which to fill. I do remember seeing Justin @ TFS doing repairs like this on manifolds and what not, and to me it does seem like he knows what he is doing and understands the big picture when it comes to these kinds of repairs.

tweake wrote:i would check out @tighappens on instagram as he does quite a bit of this type of work (and its awesome!).

this^^^^^^^

Check out how he grinds cracks out before he welds them.

Also, he was a guest on WTAT podcast recently, if you haven't listened to his interview, you should. He's in Italy.

If you haven't yet pieced it together, a repair like that is both a challenge and a liability for even the most experienced welders. Every shop owner I know, including myself, would reject that work.

It can be repaired. Anything can be repaired. But as others have mentioned, are you willing to pay the cost of that, which could easily surpass the cost of a complete replacement?

My advice: If you NEED this to be repaired, don't tackle it as a beginner. Take it to a shop which specializes in engine repairs and be prepared to pay for it.

Good luck to you.

BTW, your pics are really good. They look awesome at my house on my ~130" view. Yes this is how I read/post on forums

Thanks for everybody’s 2 cents. It all adds up to a dollar, and it helps.[emoji57][emoji16]. Ductape... lol I tried JBweld but it’s didn’t work. [emoji2357] And Yeah Oscar, I don’t think my welder has the advanced ac pulse, still a decent welder though I think. And I’ll make sure to clean really good as well as take the part off before welding it. I feel like I can do it and if not I won’t have anything to lose anyways. Hands on is the best way to learn. There’s some saying that goes... can you do it? Yes I can, but teach me first.


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TraditionalToolworks wrote:

tweake wrote:i would check out @tighappens on instagram as he does quite a bit of this type of work (and its awesome!).

this^^^^^^^

Check out how he grinds cracks out before he welds them.

Also, he was a guest on WTAT podcast recently, if you haven't listened to his interview, you should. He's in Italy.

I have. Indeed some awesome stuff. I’m now following him. As well as Mark Winchester.


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Oscar wrote:BTW, your pics are really good. They look awesome at my house on my ~130" view. Yes this is how I read/post on forums

Thanks. And that’s awesome[emoji2937]


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