The International Cessna^® 170 Association

I forgot about the manifold in there.
Yeah, it's a complicated cast.

3D printing?

Even if you could find some one to cast a sump, you couldn't just use the old one as a pattern. There's on the order of about 6-7% shrinkage from molten aluminum to room temp.

That's pretty much a consensus that casting is not the way to go--and then Miles our assn. engr throws another problem out there. Now if we used the pan as a mold and then cast a new block and accessory cast and they all shrunk 6-7% we'd be in good shape --right Miles nothing else would fit So, coating is the way to go--Now a DER???? Know a helpful one anybody? Ron

Casting sounds expensive..while working for Wolf Creek, we had a small oil recirculating pump cast by a foundry out in eastern PA. I think it was somewhere in the neigborhood of 120K. It was just cast iron. ..and that was about 15 years ago.

Just weld it, there are hundreds of places that weld mag.

including me.

I've been led to believe that contamination in the bottom of of an old cast magnesium oil sump almost always precludes acquiring a successful bonding of the weld.

If the sump is weld repaired and it still fails inspection, at that point it is junk. If the case is only cracked and there are no holes thru the case, try to get it epoxy repaired first. Okanagan will NOT epoxy repair a welded case. They will send it back unmolested if they can't repair it, then you can procede with weld repair options as a last resort.

I went thru the weld-first option and my sump still failed due to cracks propagating from the weld repair area. They kept chasing cracks until they gave up. That sump was then junk, Okanagon wouldn't touch it.

Luckily, the engine overhauler had another case and it was sent for epoxy repair first. It came back repaired. I asked how long it would last and the guys in Kelowna said they had engines come thru for the third overhaul since repair and they still passed inspection. Good enough for me.

blueldr wrote:I've been led to believe that contamination in the bottom of of an old cast magnesium oil sump almost always precludes acquiring a successful bonding of the weld.

You have been miss lead.

hilltop170 wrote:If the case is welded and it still fails inspection, at that point it is junk.

Who says ?

a chunk of magnesium is always going to be a chunk of magnesium. and can be welded over and over again.

it simply must be done correctly.

the TIG method was invented during WWII to weld mag and has been doing a fine job in the right hands ever since.

The reported number of failed repairs on welded contaminated magnesium crankcase sumps can't all be due to lack of ability of the welder or use of the wrong welding equipment. There are a VERY few A&P mechanics that can qualify as certified welders and very few of them would even attempt to do that repair. Even with TIG equipment, it's not like doing mild steel or CM tubing.

T. C. Downey wrote:

hilltop170 wrote:If the case is welded and it still fails inspection, at that point it is junk.

Who says ?

a chunk of magnesium is always going to be a chunk of magnesium. and can be welded over and over again.

it simply must be done correctly.

the TIG method was invented during WWII to weld mag and has been doing a fine job in the right hands ever since.

Tom, what was meant by "junk" was in reference to being able to have subsequent epoxy repair done on the sump after a weld repair. Okanagan will not epoxy repair a welded case.

However, to answer your question, if a weld repair fails inspection, the sump is junk unless a later weld repair passes inspection. I suppose repairs could be attempted until the entire sump has been replaced but at some point economics will dictate.

The repair shop that could not manage to get a good weld repair on my sump stated porosity of the cast magnesium is such that impurities which impregnate the casting during engine operation, and prevent good welds, are impossible to remove from the casting before welding.

hilltop170 wrote:

T. C. Downey wrote:

hilltop170 wrote:If the case is welded and it still fails inspection, at that point it is junk.

Who says ?

a chunk of magnesium is always going to be a chunk of magnesium. and can be welded over and over again.

it simply must be done correctly.

the TIG method was invented during WWII to weld mag and has been doing a fine job in the right hands ever since.

Tom, what was meant by "junk" was in reference to being able to have subsequent epoxy repair done on the sump after a weld repair. Okanagan will not epoxy repair a welded case.

However, to answer your question, if a weld repair fails inspection, the sump is junk unless a later weld repair passes inspection. I suppose repairs could be attempted until the entire sump has been replaced but at some point economics will dictate.

The repair shop that could not manage to get a good weld repair on my sump stated porosity of the cast magnesium is such that impurities which impregnate the casting during engine operation, and prevent good welds, are impossible to remove from the casting before welding.

Did they even try? Mag contamination is the major cause that many shops will not weld a 0-300 sump. But think about it, if Mag was that porous wouldn't it leak?

Each and every pit must be ground out to clean metal, that takes time, they can't charge you for all that time and keep you happy. I can clean each pit, and will charge you for the time. you want it fixed right, that costs money.

many shops will not weld to a threaded hole, because putting the threads back is a real PITA.

My curiousity is aroused as to what kind of a warranty is offered by the people that repair these magnesium oil sumps.