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Success! Notes for anyone who is interested Posted by sam96CS [Email]  (#852) [Profile/Gallery]
(more from sam96CS) on Fri, 17 Aug 2012 12:38:38
In Reply to: Downpipe to turbo connection, sam96CS [Profile/Gallery]
, Thu, 16 Aug 2012 17:27:56
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Thanks to all for all the advice. I tried Mr. Bubble's suggestion, and it worked. Here is a writeup of what I did, starting with how I located the exhaust leak.
PROCEDURE:
I listened through a few feet of garden hose to locate the leak. It was at the back side (engine block side) of the downpipe to turbo connection. Inspection with a mirror found no cracks in the pipe. The 3 nuts are tight and no studs have broken, so why is the downpipe no longer pulled squarely and evenly against the turbo? I found the answer at step 4 below. I wonder now what would have happened if I had merely tightened the upper rear nut.
01. Drive onto ramps to make everything easier and more comfortable to reach.
02. Spray PB Blaster, Liquid Wrench, Kroil or whatever you prefer on the 3 nuts that attach the downpipe to the turbo. Also spray the nut that secures the stay to the rear of the Cat. I let mine soak 24 hours and sprayed multiple times with PB Blaster. I also tapped the downpipe bracket lightly near the studs with a small hammer to enhance the capillary action of the PB Blaster.
03. Use a 16mm wrench to loosen (but not remove) the bolt that attaches the rear of the Cat to the stay. I used a 5/8" wrench with a 15 degree angle on the box end. I didn't have enough leverage to turn the bolt, so I tapped the end of the wrench with a 20 ounce hammer until the bolt started turning. In retrospect this step probably could have been skipped.
04. Use a 13 mm box wrench to remove the 3 copper nuts that hold the downpipe to the turbo. I used a Kobalt brand combination wrench (sold by Lowes) that is 6-3/8" long with a 12 point box end angled at 15 degrees. It worked at all 3 locations. Problem: the stud came out with the top rear nut. This is where I found the leak. The stud probably was not fully seated after 185,000 miles of vibration and thermal cycles.
05. Put a box or whatever under the downpipe to support its weight when it is pulled off of the studs. I used a jack stand to support the downpipe just in front of the Cat. This step turned out to be unnecessary.
06. Use a big standard screwdriver to lever the downpipe off of the turbo. I bumped it loose by tapping the big screwdriver with a deadblow hammer. The front O2 sensor limits the downpipe's travel to about 3/8". Not enough to clear the studs, but enough to do the last step.
07. Smeared anti-seize on the flange. Based on Mr. Bubble's advice I decided to screw in the upper rear stud using the stuck bolt. The stud is 35mm long, and 10mm goes into the turbo. So I figured I would tighten it until snug, and if the stud stuck out no more than 25mm (1 inch) from the turbo, then it must be fully seated. I used a pipe cleaner to make sure there is no crud in the turbo's hole for the stud. I tightened the other 13mm nuts also and the 16mm bolt at the rear of the Cat. I alternated tightening the 13mm nuts to keep the downpipe's flange square to the turbo. Started the engine and let it warm long enough to cook off the PB Blaster and anti-seize. No more exhaust leak.
From now on I'll make sure the 13mm nuts are snug at every oil change.
, Thu, 16 Aug 2012 17:27:56, Fri, 17 Aug 2012 12:38:38 <-- Viewing This Message
, Thu, 16 Aug 2012 18:02:05, Thu, 16 Aug 2012 18:15:30, Thu, 16 Aug 2012 18:09:06, Thu, 16 Aug 2012 18:00:09, Fri, 17 Aug 2012 10:00:48, Fri, 17 Aug 2012 13:57:19
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