Broken water pump stud

[zerokreap]

So, I've got this older sports car I'm working on, and in the middle of a timing belt and water pump job, a corroded M6 stud snapped flush with the aluminum engine block. Most folks in my car forum advised against extractors, saying they could make things worse, and instead suggested welding a washer to the stud, then a nut to the washer. I know this is a common trick, but I'm struggling to make it work.

I hadn’t welded in 20+ years, so I picked up a Titanium Easy-Flux 125 from Harbor Freight, practiced on some scrap steel, and went to work. But after three days and about 30 attempts, I still can't get a washer to fuse to the stud. The weld pool looks molten, and everything seems to be getting plenty hot, but the washer always breaks loose.

The welder’s voltage/amperage range is 15.5V/30A to 20.3V/125A, with settings from A to J. I started at a medium setting and have gradually stepped it up—right now, I’m at about ¾ power on both voltage and wire speed, but I still don’t think I’m getting enough heat into the stud itself.

With an M6 fastener, the working area is tiny, so penetration is tricky. Would preheating the stud with a butane torch help, or is that risky with an aluminum block? Should I max out the welder settings, or is my technique more likely the issue? Any advice for making this work with flux-core? Appreciate any insights!

 

[frank horton]

it's a very tricky job on a stud this small......
I'd go for a left handed drill bit on a stud so small......warming the block won't do any harm but it will not do much good as the ally will rob all the heat very quickly....
often as u drill (in reverse remember) as u get towards the middle of the broken stud there's usually enough heat and friction for it to just unscrew said stud....
Please make a new stud from brass when u refit the pump.....
when I do repairs of this nature on antique vehicles I always make up brass nuts / bolts n studs....

 

[RWD3M]

Can you post a picture of the culprit? It may help us to come up with ideas based upon access etc..

 

[dave h 2]

Try an m6 nut held with mole grips, hold the torch at 90 deg to the block/head in the middle of the hole and fill with weld on full power. The nut will also protect the block from being welded.

Water pumps, exhaust and thermostat studs are always bad like this. When undoing and you feel the wrench go just a bit springy STOP as it's nearly shearing. You get about another 1/8th of a turn so its a fine line. Sometimes tightening the bolt first works and sometimes you have to work it back and forth a bit at a time and the threads still may strip.

 

[tom2207]

I do lots of this ,, find a wee bit of copper sheet , say 1mm , drill a hole in it say 7mm and place it over the stud , and put a decent tack onto the stud , then do it again and again and again , let the heat soak into the stud , after a few mins you will have enough new weld metal sticking out to hold with a pair of vise grips , but , let it cool , when its cooling down but still just warm ish add oil to the stud , just good old engine oil [ I use acf50] ,, then when its cooled down it should turn out with vise grips its the heat and then the cooling cycle that does good , dont bother trying to turn it out hot as everything is expanded and tight , when it cools the expansion will have happened and the rust seal will be broken and the steel will contract back away from where it one was,,,, counter intuitive but dont knock it until you try it , Ive never been beaten yet on stud removal .

 

[not done it yet]

I agree with Frank. LH drill set is my goto for these sorts of job.

I would start with a 1.5-2.0mm normal RH drill to carefully get as close to centre as possible, steadily enlarging the hole and then changing to my LH drill set to incrementally increase the drill size to the core diameter. The offending item will generally unscrew as the core diameter is approached.

 

[MikeBs]

Nothing to add to above, but just wanted to say ‘I feel your pain’.
Have been in a similar position on an old sports car twice. First time was an absolute disaster using an Easyout. Second time was an absolute dream with an Easyout.
Good luck, I couldn’t get a welder in there for either of mine.

 

[Pigeon_Droppings2]

I do lots of this ,, find a wee bit of copper sheet , say 1mm , drill a hole in it say 7mm and place it over the stud

This is how I do it...but the torch I think needs to be at 90 degrees and the mig wire must hit the broken stud precisely...which is often the difficult bit.

I only use gas mig...never tried this with flux cored wire though....maybe someone else on here has?

 

[tom2207]

This is how I do it...but the torch I think needs to be at 90 degrees and the mig wire must hit the broken stud precisely...which is often the difficult bit.

I only use gas mig...never tried this with flux cored wire though....maybe someone else on here has?

the copper sheet buys you a lot of give and taake and allows for a bit of leeway , a copper washer would do at a push , but I usually just cut an inch off a bit of 15mm copper water pipe then slit it and open it up to make a sheet , its plenty big enough and tough enough for most of the jobs I do ,

 

[Argonman]

I restore old Japanese motorcycles. M6 fasteners and aluminium blocks are common. They become especially troublesome when associated with water pump fastenings.

You need to find a way of giving the end of the broken stud a thorough clean back to bare metal. This can be difficult if there is not much stud protruding. Nevertheless you need to do it to stand half a chance of making a decent weld. With an m6 stud i rarely need to go down the washer route. I have most success by building up a blob of weld on the end of the stud. Enough to get a good set of Irwin vice grips on the blob.

once the blob has cooled down give it a healthy smack with a hammer. Get the vice grips on and carefully begin a light tightening and undoing motion on the blob. Don’t over do it. If you are lucky you will eventually feel the tiniest amount of movement. Keep up this action and the movement will increase unti eventually it will screw out. This really is an art and it comes with experience. You may need to repeat this weld and undo process a few times before you are successful.

If you do go down the washer/nut route it is essential that you remove the shiny zinc coating from them before you try to weld. You will not get a good strong weld if its contaminated with zinc.

Hope this helps. Regards. Chris

 

[Gareth J]

I restore old Japanese motorcycles. M6 fasteners and aluminium blocks are common. They become especially troublesome when associated with water pump fastenings.

You need to find a way of giving the end of the broken stud a thorough clean back to bare metal. This can be difficult if there is not much stud protruding. Nevertheless you need to do it to stand half a chance of making a decent weld. With an m6 stud i rarely need to go down the washer route. I have most success by building up a blob of weld on the end of the stud. Enough to get a good set of Irwin vice grips on the blob.

once the blob has cooled down give it a healthy smack with a hammer. Get the vice grips on and carefully begin a light tightening and undoing motion on the blob. Don’t over do it. If you are lucky you will eventually feel the tiniest amount of movement. Keep up this action and the movement will increase unti eventually it will screw out. This really is an art and it comes with experience. You may need to repeat this weld and undo process a few times before you are successful.

If you do go down the washer/nut route it is essential that you remove the shiny zinc coating from them before you try to weld. You will not get a good strong weld if its contaminated with zinc.

Hope this helps. Regards. Chris

This. To the letter. Removed several sheared M6 tinwear screws out of air-cooled VW aluminium this way successfully. Some even sheared below the surface a bit. Also never bothered with shielding the aluminium. Although that might be more important on a gasket sealed surface.

I would think it would be a lot harder with gassless mig though.

 

[zerokreap]

Wow, I'm overwhelmed but the response here. The car forum was not so helpful, ha!

I should have mentioned that the stud has some Loctite on it...so, I doubt the left-handed drill will work. I soaked the stud with penetrating oil every day for two weeks before I even tried to loosen it...then, when I attempted, it didn't turn at all...just twisted, then broke. So, I seriously doubt anything other than this weld trick, or drilling it out, will work.

I see a lot of good suggestions here. I'm going to read through them carefully, then give one of more a try. We've got a horrible storm system coming through tomorrow, so it will probably be Sunday before I'm at it again.

Here are some pics. You can see both the broken stud, which looks like it has a little bit of a weld stuck to the end of it, as well as what they look like when they're not broken, just to the right of that.

 

[zerokreap]

it's a very tricky job on a stud this small......
I'd go for a left handed drill bit on a stud so small......warming the block won't do any harm but it will not do much good as the ally will rob all the heat very quickly....
often as u drill (in reverse remember) as u get towards the middle of the broken stud there's usually enough heat and friction for it to just unscrew said stud....
Please make a new stud from brass when u refit the pump.....
when I do repairs of this nature on antique vehicles I always make up brass nuts / bolts n studs....

There is some thread lock involved. So, I just have serious doubts that an extractor is going to work. That said, I may give it a try if I cant get the welding truck to work.

I do have a new set of studs already. I'll use some thread sealant (rather than lock) this time to prevent any moisture penetration into the threads.

 

[zerokreap]

Can you post a picture of the culprit? It may help us to come up with ideas based upon access etc..

Done. See above post.

 

[zerokreap]

Try an m6 nut held with mole grips, hold the torch at 90 deg to the block/head in the middle of the hole and fill with weld on full power. The nut will also protect the block from being welded.

Water pumps, exhaust and thermostat studs are always bad like this. When undoing and you feel the wrench go just a bit springy STOP as it's nearly shearing. You get about another 1/8th of a turn so its a fine line. Sometimes tightening the bolt first works and sometimes you have to work it back and forth a bit at a time and the threads still may strip.

Understood. I'll keep this stuff in mind. Thanks for the tips!

 

[zerokreap]

I do lots of this ,, find a wee bit of copper sheet , say 1mm , drill a hole in it say 7mm and place it over the stud , and put a decent tack onto the stud , then do it again and again and again , let the heat soak into the stud , after a few mins you will have enough new weld metal sticking out to hold with a pair of vise grips , but , let it cool , when its cooling down but still just warm ish add oil to the stud , just good old engine oil [ I use acf50] ,, then when its cooled down it should turn out with vise grips its the heat and then the cooling cycle that does good , dont bother trying to turn it out hot as everything is expanded and tight , when it cools the expansion will have happened and the rust seal will be broken and the steel will contract back away from where it one was,,,, counter intuitive but dont knock it until you try it , Ive never been beaten yet on stud removal .

That's a good idea and may be the best way to go here. Thanks!

 

[zerokreap]

the copper sheet buys you a lot of give and taake and allows for a bit of leeway , a copper washer would do at a push , but I usually just cut an inch off a bit of 15mm copper water pipe then slit it and open it up to make a sheet , its plenty big enough and tough enough for most of the jobs I do ,

I actually have a bit of copper pipe laying arrive from a repair job this past year...I never their away anything that might be useful later, ha!

 

[zerokreap]

I restore old Japanese motorcycles. M6 fasteners and aluminium blocks are common. They become especially troublesome when associated with water pump fastenings.

You need to find a way of giving the end of the broken stud a thorough clean back to bare metal. This can be difficult if there is not much stud protruding. Nevertheless you need to do it to stand half a chance of making a decent weld. With an m6 stud i rarely need to go down the washer route. I have most success by building up a blob of weld on the end of the stud. Enough to get a good set of Irwin vice grips on the blob.

once the blob has cooled down give it a healthy smack with a hammer. Get the vice grips on and carefully begin a light tightening and undoing motion on the blob. Don’t over do it. If you are lucky you will eventually feel the tiniest amount of movement. Keep up this action and the movement will increase unti eventually it will screw out. This really is an art and it comes with experience. You may need to repeat this weld and undo process a few times before you are successful.

If you do go down the washer/nut route it is essential that you remove the shiny zinc coating from them before you try to weld. You will not get a good strong weld if its contaminated with zinc.

Hope this helps. Regards. Chris

Yeah, I think it was the zinc that was causing problems. I didn't know it was such an issue...I was planning to pick up some uncoated hardware tomorrow from a different shop. Though, I may just go with building up the blob, as you've suggested. Thanks so much for sharing your thoughts!

 

[not done it yet]

the stud has some Loctite on it...so, I doubt the left-handed drill will work. I soaked the stud with penetrating oil every day for two weeks before I even tried to loosen it...

Why not? Once you get to the core diameter (if it didn’t work) you then use a pick to remove the tread remnants.

Can’t see that penetrating oil is going to get anywhere with a thread sealant in there, either.

 

[zerokreap]

This. To the letter. Removed several sheared M6 tinwear screws out of air-cooled VW aluminium this way successfully. Some even sheared below the surface a bit. Also never bothered with shielding the aluminium. Although that might be more important on a gasket sealed surface.

I would think it would be a lot harder with gassless mig though.

This is very similar, though not air-cooled...Porsche 968. I tell ya, I'm wishing this was an air-cooled 911 right now!

I've been cleaning the end of the stud with the wire brush attachment on my Dremel. I feel like it has been working pretty well. What do you think, is something like that good enough? I added some pics above, in case that helps. Thanks for chiming in!