crack in gearbox casing

[odonnellkevin]

you might remember I was stuck with a filler plug that I couldnt shift, so put into garage to let the "proffesionals" sort it.

not only did it still leak after replacing the plug, there is now a hairline crack 3mm long starting at the filler plug hole.

after usual shouting match they have agreed to get it fixed (elsewhere) by grinding a groove and tig welding it. I was thinking more along the lines of a liquid metal type compound to fill it after grinding the groove

Opinions welcome, if you have time

Cheers again, Kevin.

[flatmajor]

hi, you could do all those things also you can get gear box sealent to put in your engine abit like k seal and rad weld just for time being. alot of people would not reckormend it but ive doneit myself and had no bad effects. i cant remember what the stuf is called, halfrauds does ther own brand of the seal. cheers

[streaky]

I wouldn't use the liquid metal type fixes or any of the two part epoxy resins that claim to fix cracks etc.
The oil will eventually weaken the bond bewteen the casting and the repair and you'll end up with a leaking crack. It would only be a temporary fix.

Tigging + machining/re-taping the thread would be the best solution IMHO or you can use the other option of HLS2000 which is also good for aluminium castings.

[TEMPL4R]

We get this a few times with BMW sumps, overtightened and the sump cracks. We usually take the sump off and have it welded.

I have tried one with a long spark plug rethread insert and Loctite, that seems to be working OK. If it's still OK when I service it next time, that is what I will try doing again, it will save a couple of hours labour.

Chris

[odonnellkevin]

Thanks for all the advice. As usual I wasnt clear in my description. The crack starts at the outer rim of the filler plug hole along the outer casing for 3mm. The reason I am wary of the welding option is the chance of a sandhole or other weakness in the cast around the damaged area, and the unknown skill of the welder the garage want to do the repair. There is no way they will entertain dropping the box, it will be done in situ, so if they drill a hole to stop the crack spreading, drill and tap a new thread or grind in too far the swarf will end up in the box.

The garage are doing this without good grace so I think I will get someone else to repair it, and sadly find another garage to deal with.

customer service, oxymoron
( the only thing I remember from english lessons)

P.S.
Dont do what I did when replacing the heater matrix and remove half the dash. read the posts on how to do it first.

[Richie_asg1]

As this is on alloy, all the methods stated are likely to work - as this is a pressure crack - and only the start of one.
3mm ?
how are they going to grind that?

As for welding - being alloy it should be preheated first - and this won't be possible in situ without possibly damaging seals or setting fire to whatever oil in in there.

Cleaning the crack to remove all oil will be impossible prior to welding.

I may be wrong, but I think using a metal stitching screw would be better, followed by filing the overhang of that screw to match the minor diameter of the plug hole, then re-tapping to clear the threads and expand the plug hole to a usable size to match the plug.

By using a metal stitch, the hole for the screw would serve as a stress relief for the end of the crack - to stop it spreading further, and when tightened, the screw would form an oil tight seal. Being alloy itself - it could be finished to match the rest of the casting after installation.

Castmaster (pins) screws would seem ideal for this -
http://www.locknstitch.com/Repair%20pdf%20files/Aluminum%20crack%20inspection%20and%20repair%20exa mples.pdf