I wanted to keep this discussion going with my recent trials and tribulations regarding my TA-49 turbo rebuilt by PTE...
I had my TA-49 rebuilt over the winter, as it has been on my car for about 10 years. I was having the small oil leak at the bottom exhaust housing bolts as the OP described. I thought a refresh would help. PTE rebuilt the turbo over winter, and I finally got it installed about a month ago. Two other winter projects were to install my GSCA headers and a GBody turbo oil drain, both of which were completed before I reinstalled the turbo.
The first time I fired my car up in the garage, no problems. The second time I fired my car up and took it for a short drive, no problems. The third time I fired up the car, I just backed it out into the driveway so I could wash it. No problems. When I fired it up to pull it back into the garage, this happened:
Blue oil smoke pouring out of the tailpipes (even at idle) and oil dripping out between the exhaust housing and downpipe. Not good. My first thought was that PTE did something wrong, as others in posts above indicated. The next night, I pulled the turbo off and found the following:
Oil had obviously gotten into the turbine and downpipe. After discussing this with Bison (big thank-you, BTW), we bounced around two ideas - either PTE dropped the ball, or maybe there was a problem with my oil drainage. The oil seals on a turbo are not positive seals like your rear main. It is just a piston ring that isn't designed to be submerged in oil. There is also a slinger that will fling any stray oil away from the piston ring seal, but then again it's not designed for submersion. If the oil drain is not free-flowing enough to allow the oil coming from the journal bearing to freely return to the block, it will pool up to the seals and go through them under conditions where there is not positive pressure in the turbine (like idle speed...). So, I wanted to confirm my drainage. When I installed it, I tried my best to make sure that its slope was always downhill, and I at least got it similar to the stock drain's path:
Per Bison's suggestion, I decided to see how fast the Gbody drain could swallow a quart of oil as-installed on the engine. Simple test, as shown in the photo below:
It took about a minute and 25 seconds. At several times, I had to stop pouring oil into the funnel because the oil was filling up the drain and overflowing. I then tried the same test on my old stock drain holding it in the same orientation as it would be on the engine:
It took about a minute and 10 seconds. However, I noticed that the stock drain could swallow the oil as quickly as it came out of the full funnel. In other words, the funnel was now the limiting factor. If I had used a bigger funnel, the time would have been lower. My conclusion was that the stock drain is able to freely flow more oil than the GBody drain. I did some further investigating, and I've read that PTE recommends a minimum drain size of -10AN (5/8"). Others on this board are reporting that they are using -8AN (1/2") and having no problems. So, I measured the fittings (not the hose, but the hose barbs) on the GBody drain. At the points where the hose connects, the ID of the hose barbs are only 3/8" in diameter (equivalent to -6AN). In fact, the OD of the hose barb can fit inside the ID of the stock oil drain:
So, I reassembled the turbo onto the engine using the stock oil drain. I've now started and driven the car twice, and the oil smoke and leaks through the turbine are completely gone. Admittedly, it took three starts for the problem to appear the first time, so maybe I'll try it again next weekend and the problem will come back. If it does, I will post back here.
The point of this is not to bash anybody's product. I like the design of the GBody drain, it's easy to install and looks nice. I am thinking that maybe a product improvement can be made by widening out the ID of the hose barbs to make the drain flow better. I know many others have used this drain with no problems, but it doesn't appear to be adequate on my car. The point of this post is simply the following: If you are having problems with oil leaking out of your turbine, consider your oil drain. It's very important to the proper operation of your turbo's seals.
Hopefully, after writing all of this, my problem won't return next week!
One other thing - I did some research, and Turbonetics recommends that the oil drain angle be within 15 degrees of true vertical to promote good drainage flow. I measured the angle of my turbo with a protractor and bubble level, and it's tilted back about 20 degrees. Next time I remove the turbo, I am planning to rotate the center section a little bit to get it within the 15 degree limit. If you're installing a turbo, it's good to get the turbo feed and drain closer to true vertical than I have.
Hopefully my stress will help somebody else avoid this problem.
I had my TA-49 rebuilt over the winter, as it has been on my car for about 10 years. I was having the small oil leak at the bottom exhaust housing bolts as the OP described. I thought a refresh would help. PTE rebuilt the turbo over winter, and I finally got it installed about a month ago. Two other winter projects were to install my GSCA headers and a GBody turbo oil drain, both of which were completed before I reinstalled the turbo.
The first time I fired my car up in the garage, no problems. The second time I fired my car up and took it for a short drive, no problems. The third time I fired up the car, I just backed it out into the driveway so I could wash it. No problems. When I fired it up to pull it back into the garage, this happened:
Blue oil smoke pouring out of the tailpipes (even at idle) and oil dripping out between the exhaust housing and downpipe. Not good. My first thought was that PTE did something wrong, as others in posts above indicated. The next night, I pulled the turbo off and found the following:
Oil had obviously gotten into the turbine and downpipe. After discussing this with Bison (big thank-you, BTW), we bounced around two ideas - either PTE dropped the ball, or maybe there was a problem with my oil drainage. The oil seals on a turbo are not positive seals like your rear main. It is just a piston ring that isn't designed to be submerged in oil. There is also a slinger that will fling any stray oil away from the piston ring seal, but then again it's not designed for submersion. If the oil drain is not free-flowing enough to allow the oil coming from the journal bearing to freely return to the block, it will pool up to the seals and go through them under conditions where there is not positive pressure in the turbine (like idle speed...). So, I wanted to confirm my drainage. When I installed it, I tried my best to make sure that its slope was always downhill, and I at least got it similar to the stock drain's path:
Per Bison's suggestion, I decided to see how fast the Gbody drain could swallow a quart of oil as-installed on the engine. Simple test, as shown in the photo below:
It took about a minute and 25 seconds. At several times, I had to stop pouring oil into the funnel because the oil was filling up the drain and overflowing. I then tried the same test on my old stock drain holding it in the same orientation as it would be on the engine:
It took about a minute and 10 seconds. However, I noticed that the stock drain could swallow the oil as quickly as it came out of the full funnel. In other words, the funnel was now the limiting factor. If I had used a bigger funnel, the time would have been lower. My conclusion was that the stock drain is able to freely flow more oil than the GBody drain. I did some further investigating, and I've read that PTE recommends a minimum drain size of -10AN (5/8"). Others on this board are reporting that they are using -8AN (1/2") and having no problems. So, I measured the fittings (not the hose, but the hose barbs) on the GBody drain. At the points where the hose connects, the ID of the hose barbs are only 3/8" in diameter (equivalent to -6AN). In fact, the OD of the hose barb can fit inside the ID of the stock oil drain:
So, I reassembled the turbo onto the engine using the stock oil drain. I've now started and driven the car twice, and the oil smoke and leaks through the turbine are completely gone. Admittedly, it took three starts for the problem to appear the first time, so maybe I'll try it again next weekend and the problem will come back. If it does, I will post back here.
The point of this is not to bash anybody's product. I like the design of the GBody drain, it's easy to install and looks nice. I am thinking that maybe a product improvement can be made by widening out the ID of the hose barbs to make the drain flow better. I know many others have used this drain with no problems, but it doesn't appear to be adequate on my car. The point of this post is simply the following: If you are having problems with oil leaking out of your turbine, consider your oil drain. It's very important to the proper operation of your turbo's seals.
Hopefully, after writing all of this, my problem won't return next week!
One other thing - I did some research, and Turbonetics recommends that the oil drain angle be within 15 degrees of true vertical to promote good drainage flow. I measured the angle of my turbo with a protractor and bubble level, and it's tilted back about 20 degrees. Next time I remove the turbo, I am planning to rotate the center section a little bit to get it within the 15 degree limit. If you're installing a turbo, it's good to get the turbo feed and drain closer to true vertical than I have.
Hopefully my stress will help somebody else avoid this problem.
