Repairing cracks in cast iron

I have a number of small cracks I need to repair in one of my engines

In the first instance I am thinking about silver soldering, (or soft solder if this would be better) and wondered if anybody could tell me the best flux/solder combination to try

This is a large section of iron so getting a very high temp might be a problem

I plan to vee the cracks then run solder into the vee, perhaps with a bit copper wire wedged into any gaps that are too wide

My second option is a combination of the copper wire wedge and some chemical solution, I was thinking about some of the seek n seal type products run in to the crack after the copper wire with a top layer of JB weld in the vee groove

Any suggestions would be appreciated

Thanks

Dougie

Despite seeing much advice against it, I have been able to sliver solder two cast iron pieces together successfully with a joint area of around half a square inch. they were freshly prepared surfaces though, not cracked surfaces contaminated with oil. I just used easyflow and easyflow flux.

Despite this I wouldn't put any faith in getting silver solder into a cracked casting though.

Neil

Brazing is the usual way, seen plenty of things done that way but you would need oxy -acetylene to get the filler rod hot enough.

Like neil I have silver soldered CI but have preheated the metal to get rid of the carbon, not something you can do with a crack especially if its old & dirty.

There are companies that will stitch the cracks, look in something like Old Glory where they advertise.

J

Hi Dougie,

our advice for silver soldering CI because silver solder will not flow over the graphite on the surface of the iron. remove it by heating the iron to a red heat (no flux) with the oxidizing part of the flame. That is the area outside the blue zone. Allow to cool and brush with a stiff wire brush. Apply HT5 flux and treat normally.

But as is said I don't know if this will help you with the cracks.

shaun.

I have seen cast iron welded with a high nickel filler rod, but it was all preheated to reduce stress fracturing upon cooling.

In the past I have successfully welded cracks in cast iron using coated electrodes designed for cast iron, by the electric arc process. On many occasions good results were attained without having to heat up the whole casting. It's a matter of judicious application of heat, avoiding cold draughts and not allowing the casting to cool too quickly. To date none of these repairs have failed, touch wood. This method may help with your problem. My arc welder is an SIP with a max welding current of 140 Amps.

Rick

I have repaired an external crack in a water cooled engine cylinder head by drilling a small hole at the end of the crack, partially threading with a taper tap, and screwing in a steel plug coated in Hermitite. File the projecting plug to blend in with the contour of the cylinder head surface. Then drill another hole that overlaps slightly the first plug, following the line of the crack, tap it and plug it in the same way. Continue doing this all along the line of the crack.

I did this repair to an old Jowett Bradford Van engine many years ago. The engine was in use for many years afterwards.

Mike

Thank you for the above advice, it is very helpful

I have repaired other part of the crankcase using brazing but had trouble stopping the flux from burning ( pure borax )

The explanation about the carbon above explains why I could melt the rods but it just pooled

If I cut a vee along the crack and then followed the advice about heating and cooling before cleaning and fluxing then it might work

This is a water jacket on a single cylinder Aster engine that has been split by frost, it has a number of previous attempts at repairs, some welded some soft solder, I want to remove traces of these and have a relativly smooth finish

I have also thought about trying the epoxy route I mentioned above. Would the likes of JB weld be flexible enough to take the thermal expansion, perhaps with some kind of sealant applied to the inside of the very rusty inside?

Thanks

Dougie

JB Weld would be my first choice, it takes six hours to even start curing, but after 24 it should be completely set, I'm sure you'll be surprised by the results you can get with this bonding.

Hi Dougie

I have a 1908 Gardener gas engine and many years ago my late father used it to drive a circular saw and one night it froze and split the water jacket, the welder where he worked arc welded it and i still have it to this day with no leaks.When i worked at a large haulage firm in Grimsby 40yrs ago i saw a company come and stich a AEC cylinder block like Michael says by brilling and threading, the split was about 10" long and it worked untill the lorry was scraped many years later.

Regards

Stan

Hi Dougie,

I have an old Myford C/I countershaft that was badly cracked by the swing arm.

I took it into night school and the welding instructor managed to braze it using oxyacetylene. He was certainly swearing good deal by the time he finished it though - so I gathered that he didn't find it too easy. He did say that as a last resort I might have to 'peg' it (drill and tap either side with mild steel 'pegs' and that then he would try to "stitch" across them with welds - but fortunately the brazing took. It's still Ok today too (just not pretty).

I've used JB Weld to fill blow holes in castings I wanted to machine and it worked OK for that (although there is some shrinkage as it sets) but I'm not sure I'd trust it under any real stress - even though the blub says you can... I think I'd try to find a really good welder first and get his thoughts on it.

Regards,

IanT

Edited By IanT on 07/01/2014 19:58:49

Is it possible to "thin" JB weld so that it could br forced into the cracks through a syringe and needle, say 12 or 14 gauge

Dougie

Not tried it but they say Acetone will thin it, bottom of page

J

I've never used JB Weld, but probably a similar item is Doublebond two part aluminium epoxy **LINK**

Mainly used in the aero industry, and I have successfully used it to repair many cast iron cracks (Lister L type water jacket, Mercruiser exhaust water jacket, Landrover cylinder block damaged by failed head gasket blow-by to name a few).

It's not cheap, approx £60 a kit but lasts for ages, it also thins after mixing and will run into a crack if gentle heat is applied to the cracked part before application of the resin.

It takes about 24hours to fully set and can then be drilled, filed and even thread tapped.

**LINK**

Mick and Dougie-

Just FYI JB Weld is rated for service at 500 deg F or less max, according to their website.

If your engine never reaches 500 F the stuff may work OK, but I would recommend bronze welding as others have, for repairing cast iron in general. V-groove the crack area to expose clean metal and allow a space for a good chunk of weld filler metal to flow in (rather than just the crack volume). Preheat the whole workpiece before bronze welding to dull red or just below it to minimize the chance of the crack opening further due to stress from thermal expansion. Just before welding, while the workpiece is hot, brush the weld area vigorously with a stainless steel brush to remove any oxides. Apply some flux bits broken off the cold end of the bronze rod to the weld area. Bronze weld immediately at high red to low orange temp with oxy acetylene for a good repair. Any good welding supply shop can supply bronze rod - just tell them you are working on cast iron parts.

JD

Thanks for the link to Sifbronze Lofty - it seems it was specifically developed with cast iron in mind, so should do the trick. I've often read LBSC talking about "Sifbronzing" his engine frames but never used it myself.

I had a browse around their site and found this little bit of history that I found interesting - linking Sifbronze to Suffolk Punches (Lawnmowers) for instance....

**LINK**

Regards,

IanT

TIG brazing with sifbronze tig rods?

Dougie,

Got some Sifbronze No 1 rods available and you are welcome to some foc if you think they may be of use. If so , please send me a PM and I will post.

Trevor.

Hi Trevor and thankyou for the offer

I have some sifbronze rods but the problem is getting the iron hot enough

From the advice above I think in the first instance I might try to braze, I have a oxy propane setup but I need to buy the correct nozzle for this setup as the acetylene tips I have dont work

On that note, can anyone tell me what kind of nozzle/tip I need for oxy propane?

Thankyou

Dougie