Need Help Repairing Pitting in Magnesium Chain Cases!
 

I have two chain cases in my 964 engine that are made of Magnesium that are damaged by small single pits to broad pitted areas (most less than 1/16" wide by 1/32" deep...but a few up to 1/8" wide and 1/16" deep) in both cases on both sides. Some of the single pits and small groups of pits are on the machined surfaces where the gaskets will be located. Some of the single pits are at the point where oil journals join together with the gasket in between. Some single pits are at the outlet of the bolt holes through the cases where bolts pass to secure them to the engine. Most of the broad pitted areas are not in places where they threaten oil containment, but could be in the future if some larger pits penetrate the case.

Whether the pitting was caused when the mechanic aggressively cleaned the cases with high-pressure cleaning fluid...or maybe abrasive blasting; or was caused by corrosion over the 25 years the engine has existed - as the mechanic claims, I don't know.

FOUR QUESTIONS FOR THE PELICAN AUDIENCE:

1. Does someone know of a way to REPAIR pitting that can occur in the Magnesium metal chain cases?

2. Is it possible to use a liquid metal product with a hardening catalyst, apply this to the pits(s) and sand the patch(s) down to a flat profile that will work with engine heat, chemicals in the oil, etc.?

3. Is there a BETTER method to do it?

4. Has anyone successfully done this before?

;) Thanks from Florida

Get a hold of Mark...he is a great guy and will know what to do!

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/573137-82-sc-245mm-fan-housing.html

I'm replacing mine with an aluminum set for that reason!

2. Is it possible to use a liquid metal product with a hardening catalyst, apply this to the pits(s) and sand the patch(s) down to a flat profile that will work with engine heat, chemicals in the oil, etc.?

Yes it's possible to use a heat resistant two part epoxy to repair the holes. (JB Weld) But it would be extremely difficult to get a good and reliable result.
You'd have to get the magnesium parts perfectly clean before even starting. (Hot soapy water followed by a soak in acrylic lacquer thinners)

Then mix the JB Weld and fill each hole trying not to trap any air.
Once cured flatten each repaired hole and then flatten the matting surfaces for the gaskets etc.

Not an easy or simple job but new ones are $$$. I understand you're problem and wish you luck.

But IN MY OPINION the best thing to do is buy good second hand ones if available.

And whoever cleaned them for you needs to know what's happened so they don't do it again.

Pits are usually caused by moisture corrosion. Another reason to change oil at intervals according to driving style.

If replacement housings are too expensive, I'd contact a tech rep. from 3M or equivalent and ask if there's a product for this application.

There's a factory tech bulletin that describes sealing a portion of the crankcase that tends to leak using a 2-part epoxy. Your situation isn't unknown territory.

Sherwood

trowel the JB weld on with a safety razor blade so there is little or no excess to clean up. i would bead blast the area to be treated first.

post 3 mentions aluminum replacements. never heard of that. link?

Hello Pelican Responders and Viewers:
 

I appreciate all of you for responding to my urgent request for an answer to my costly predicament...especially the comment from kclem19 who mentioned there are aluminum chain casings available.

Can you tell me where you're going to get them...and how much they'll cost?

Do you know if they're available for 1990 to 1993 "964" (Carrera 2's) models?

Please let me know ASAP because my mechanic is going to have someone (fill the holes this coming Monday and I 'm not sure how well "they" can...or will...do!

I'm having to resort to this measure because I can't find a good set of used cases and the Porsche dealership wants $2,100 up here in northeast Florida!

Thanks from Florida

http://forums.pelicanparts.com/uploa...1422030650.jpg

Didn't steve @ rennsport systems mention in you other thread that he had a good set?

Post a ad in the classified section.

Hello John Walker's Workshop:
 

Do you know from experience if the JB Weld will hold up to the temperature fluctuations of the engine and chemicals in the oil...as well as work properly with the Magnesium metal itself?

Thanks from Florida

It's been used for years in situations like yours. I wouldn't hesitate to use it on a few pits where a gasket seals against it. Of course you haven't posted any pics of the pits, so they may be so bad that nothing will fix them.

Eastwood sells a compound called Lab Metal that can be thinned to fill holes easier and they also have a hi temp version as well

Lorne M.

i would fill them with jb. but you can have them welded up. It might be a bit of a challenge finding someone local to weld magnesium though.