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Case & JB Weld question

Hello all.
The photos below are of the case from my '78 911SC. The first two photos show what looks to be a reinforcement or repair made with JB Weld or similar. My case has been recently cleaned, leaving areas of deterioration in the applied substance. The second set of photos show the same area of the case after removing the substance. I don't see any failures in the case that necessitated the original application, although it appears to have been applied specifically at the point where that part of the case narrows.

I'm assuming this was not a factory application like the dowel pins on the case ends. So, my questions are, is this common or unusual, why was this done originally, and do I need to reapply? Thanks, Gary S.








Old 04-17-2011, 06:44 AM
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JB-Weld is often too "intentional" to be there on accident. I'm guessing that somebody saw what they thought was a small crack developing (or had an actual crack leaking oil) and attempted to seal it. You might not find that again unless you do some careful inspection (and maybe get out the dye-penetrant kit).
Old 04-17-2011, 07:49 AM
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You might want to get in a lot closer with those after pictures. Can't see enough this way.
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Old 04-17-2011, 07:49 AM
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That is a known area of the case that is too porous and thus can allow oil to weep through the casting (there was a Porsche technical bulletin regarding this back in the day) - the bulletin instructed techs to clean the area and apply a sealer to the surface . . .
Old 04-17-2011, 08:12 AM
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so now that it's cleaned up, put some JB back on. may or may not have been seepage there, but you can't get at the area under the cooler when the engine is together.
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Old 04-17-2011, 10:18 AM
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+1 on what Ronnie wrote, it's just done to prevent a possible leak.
Old 04-17-2011, 10:19 AM
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Known porous spot on case. My 81 has goo there as well to attempt to stop weep.
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Old 04-17-2011, 07:30 PM
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I would copy what was there... It can't hurt any.
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Old 04-17-2011, 07:37 PM
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Thanks to all who have replied.

Ronnie's.930, your response explains the JB Weld's presence. It's helpful to know that it was probably done in accordance with the tech bulletin (or to repair a leak...or both).

John Walker, yes, now that it's cleaned up, I will reapply.

As sc_rufctr says, "it can't hurt".

Gary S.
Old 04-17-2011, 09:05 PM
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Now the plot thickens...

So the pictures I posted earlier in this thread were taken just after I got my case back from the machinist. He had cleaned it, bolted it back together with the new standard main bearings in it, then checked clearances with a dial bore gauge. After returning from the machinist, I cleaned the JB Weld from the previous exterior application while the case was still bolted together.

It took me a few days to get back to it, but I unbolted the case today, and now that it's (relatively) clean, the inside part of the case that corresponds to the earlier exterior JB Weld can be clearly seen. It's not pretty, as evidenced by the photos below.

So, please weigh in - is it acceptable to apply JB Weld to the inside of the case as well? Is there some other type of repair I should be looking at here?

Gary S.




Old 04-21-2011, 08:33 PM
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I wouldn't use JB weld inside an engine.

It's great stuff and very strong but would it hold up to years and years of hot oil and thousands of heat cycles?
If you did use it you may find it again (in little pieces) when you changed the oil.
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Old 04-21-2011, 10:06 PM
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Quote:
Originally Posted by sc_rufctr View Post
I wouldn't use JB weld inside an engine.

It's great stuff and very strong but would it hold up to years and years of hot oil and thousands of heat cycles?
If you did use it you may find it again (in little pieces) when you changed the oil.

Aside from the obvious concerns, JB seems like the best, cost effective solution. Worse case scenario would be oil seepage if it ever leaked, but then, what 911 didn't leak?
Old 04-21-2011, 10:53 PM
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If it was my engine at this point of a rebuild I would have it welded and know that is was fixed right. I don't think I'd JB that at all, inside or outside. JB is really a temporary measure or quick fix. I'm sure that bit of weld would be well under a $100 dollar fix.
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Old 04-22-2011, 06:04 AM
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Does anybody have a copy of the Porsche Technical Bulletin that outlines where to apply sealant to the outside of the case? I think I get it based on the pictures, but would like any other info posted.

Thanks for the help.
Old 09-30-2011, 07:00 AM
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Quote:
Originally Posted by tonythetarga View Post
If it was my engine at this point of a rebuild I would have it welded and know that is was fixed right. I don't think I'd JB that at all, inside or outside. JB is really a temporary measure or quick fix. I'm sure that bit of weld would be well under a $100 dollar fix.
uh, no.
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Old 09-30-2011, 07:54 AM
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I think you *could* trust JB Weld there, or something similar.

1. On a non-Porsche turbo conversion I did years ago I JB Welded the turbo oil return fitting into the alu oil pain. Sold the car 100,000 miles later; no issues whatsoever with the epoxied fitting.

2. Epoxy is often used inside two-stroke motorcycle motors to change port shapes and reduce the volume inside the case. It's a time honored process, been done for years and years.
Old 09-30-2011, 07:54 AM
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Quote:
Originally Posted by fanaudical View Post
Does anybody have a copy of the Porsche Technical Bulletin that outlines where to apply sealant to the outside of the case? I think I get it based on the pictures, but would like any other info posted.

Thanks for the help.
isn't it fairly obvious? leave the inside as is.
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Old 09-30-2011, 07:55 AM
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Yes - That part was obvious - no JB Weld inside the case. I understand the need to coat the external side of the case near the "cutouts" for the oil passages on both sides of the casting web based on the photos.

What wasn't obvious to me (and hence the request for the tech bulletin) was Porsche's statement regarding the extent to which to cover those areas as well as any info about other porous areas of the case. (And yes - I did do a search.)
Old 09-30-2011, 10:13 AM
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JW speaks with mucho experience..take his advice and move on to the next thing !
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Old 09-30-2011, 10:19 AM
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Quote:
Originally Posted by porterdog View Post
I think you *could* trust JB Weld there, or something similar.

1. On a non-Porsche turbo conversion I did years ago I JB Welded the turbo oil return fitting into the alu oil pain. Sold the car 100,000 miles later; no issues whatsoever with the epoxied fitting.

2. Epoxy is often used inside two-stroke motorcycle motors to change port shapes and reduce the volume inside the case. It's a time honored process, been done for years and years.

Exactly right.

I use JB to reseal oil pick-up tubes and it seems to work fine.

The area in question is not porous. This is where Porsche bored a hole and installed a metal sleeve for the oil passage. Sometimes this tube can leak, and sometimes the tube can crack and leak. Just JB it on the inside and outside and forget about it.

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Old 09-30-2011, 12:02 PM
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