A4 leaking trans fluid dealership says porous casing.. WTF?
09-12-2005, 03:21 PM
#1
Safety Car
Thread Starter
A4 leaking trans fluid dealership says porous casing.. WTF?
I had a rebuilt trans installed last winter by the dealership under warranty. I noticed a minor trans leak (under the car on the garage floor) a few weeks ago. Dealer replaced the pan seal gasket. No luck.. Took it back today and they said the trans casing is porous. A new trans will be installed Wednesday at no charge. Does this sound right??? A porous transmission casing?
09-12-2005, 03:42 PM
#2
Safety Car
There could be an air bubble or flaw in case when it was casted. I have never heard of this, but hey, your getting a new transmission! 
09-12-2005, 03:53 PM
#3
Team Owner
porous aluminum
I had a sand casting hole in the left side diff cover.. I thought it was the famous left diff seal leak and told the Mgr at the Chevy dealership about it. They pulled the cover and found the casting hole near the top. It is unusual to have one in the tranny case but well within the realm of beliveability. Hope they got it fixed for you.
09-12-2005, 04:26 PM
#4
Race Director
I used to make diecastings for a living.
We jokingly referred to them as porosity (small air bubbles) surrounded by aluminum! All castings have porosity in them, it's just when that porosity is chained together that it causes an issue. The casting should have been pressure tested to assure it didn't leak so it probably missed that step in the rebuild process. There is a process called impregnation that can seal minor porosity with an anaerobic material.
We jokingly referred to them as porosity (small air bubbles) surrounded by aluminum! All castings have porosity in them, it's just when that porosity is chained together that it causes an issue. The casting should have been pressure tested to assure it didn't leak so it probably missed that step in the rebuild process. There is a process called impregnation that can seal minor porosity with an anaerobic material.
Last edited by BadAV; 09-12-2005 at 04:33 PM. Reason: Spelling!
09-13-2005, 07:59 PM
#10
Racer
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a hole in the casting makes sense but if your dealer is telling you that the metal is porus enough to leak fluid through it i'd look for another dealer. this guy is obviously damaged.
09-13-2005, 08:09 PM
#11
Safety Car
Thread Starter
Originally Posted by aquaholic
a hole in the casting makes sense but if your dealer is telling you that the metal is porus enough to leak fluid through it i'd look for another dealer. this guy is obviously damaged.
09-13-2005, 09:31 PM
#12
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Originally Posted by aquaholic
a hole in the casting makes sense but if your dealer is telling you that the metal is porus enough to leak fluid through it i'd look for another dealer. this guy is obviously damaged.
09-13-2005, 10:00 PM
#13
Race Director
Mwagne16 is correct that the porosity can be in the sealing surface but this would typically only be exposed if the casting surface had been machined. Machined sealing surfaces with porosity are a definite no-no!
All castings also have some amount of porosity dispersed throughout the casting. The better the metal preparation process, die design, and better controlled the casting process is, the less porosity the casting has.
The company I worked for manufactured, machined, assembled, and tested oil & fuel filter housings, valve covers, and fuel priming pumps for Caterpillar engines.
Air leaks, especially small ones, are very common when pressure testing castings. This doesn't mean the casting will leak fuel or oil but is a good indication that the casting could potentially leak. First-time capability in our process was typically about 90% with no leaks. The leaking castings were impregnated and retested, typically with another 5% passing pressure test the second time around. The remaining castings were scrapped and remelted.
All castings also have some amount of porosity dispersed throughout the casting. The better the metal preparation process, die design, and better controlled the casting process is, the less porosity the casting has.
The company I worked for manufactured, machined, assembled, and tested oil & fuel filter housings, valve covers, and fuel priming pumps for Caterpillar engines.
Air leaks, especially small ones, are very common when pressure testing castings. This doesn't mean the casting will leak fuel or oil but is a good indication that the casting could potentially leak. First-time capability in our process was typically about 90% with no leaks. The leaking castings were impregnated and retested, typically with another 5% passing pressure test the second time around. The remaining castings were scrapped and remelted.
09-13-2005, 10:30 PM
#14
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Originally Posted by BadAV
Mwagne16 is correct that the porosity can be in the sealing surface but this would typically only be exposed if the casting surface had been machined. Machined sealing surfaces with porosity are a definite no-no!
All castings also have some amount of porosity dispersed throughout the casting. The better the metal preparation process, die design, and better controlled the casting process is, the less porosity the casting has.
The company I worked for manufactured, machined, assembled, and tested oil & fuel filter housings, valve covers, and fuel priming pumps for Caterpillar engines.
Air leaks, especially small ones, are very common when pressure testing castings. This doesn't mean the casting will leak fuel or oil but is a good indication that the casting could potentially leak. First-time capability in our process was typically about 90% with no leaks. The leaking castings were impregnated and retested, typically with another 5% passing pressure test the second time around. The remaining castings were scrapped and remelted.
All castings also have some amount of porosity dispersed throughout the casting. The better the metal preparation process, die design, and better controlled the casting process is, the less porosity the casting has.
The company I worked for manufactured, machined, assembled, and tested oil & fuel filter housings, valve covers, and fuel priming pumps for Caterpillar engines.
Air leaks, especially small ones, are very common when pressure testing castings. This doesn't mean the casting will leak fuel or oil but is a good indication that the casting could potentially leak. First-time capability in our process was typically about 90% with no leaks. The leaking castings were impregnated and retested, typically with another 5% passing pressure test the second time around. The remaining castings were scrapped and remelted.
09-14-2005, 06:28 AM
#15
Race Director
I guess work knowledge is a good thing if it is directly relevant to the topic at hand, which it definitely appears to be in this case. Enough said, we'll now move on to the next topic!
09-14-2005, 09:56 PM
#16
Safety Car
Thread Starter
Thanks for everyones input. I love to give good info to other members when I can. I appreciate the same coming back. this is what makes this forum so great...
09-15-2005, 01:12 PM
#17
Melting Slicks
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NCM Sinkhole Donor
I had the same problem when my 98 was new, but at least it was a warranty repair. Took the dealer several attempts to repair, because they couldn't believe the case leaked.
09-15-2005, 08:19 PM
#18
Ask any one who has had a old cadalic northstar. The original ones had porous BLOCKS that would seep oil through the side of them. 
Its just a crappy casting. Chances are they are right. I am a tech at a mercedes dealer and usally when the change a whole trans they have a service maniger look at it and sign off on the repair. The tech was probly just hoping to get lucky with a pan gasket. Look at the brite side, at least your getting a brand new trans. 
Its just a crappy casting. Chances are they are right. I am a tech at a mercedes dealer and usally when the change a whole trans they have a service maniger look at it and sign off on the repair. The tech was probly just hoping to get lucky with a pan gasket. Look at the brite side, at least your getting a brand new trans.
