OK, so I've been road-testing my '91 Vanagon gas-to-TD conversion for a few days~150 miles. Found 3 of 4 bolts that hold turbo to exhaust manifold (Quantum TD) had worked loose, though I had torqued to spec in manual. Any suggestions on how to keep these tight? Best thing I can think of is to drill small holes and safety wire heads together.
I have heard from a couple sources that they are single use bolts. Can anyone confirm or deny?
This is not a common problem I am aware of (I have never had my turbo to manifold bolts loosen up... torqued to the factory spec.) So it leads me to wonder if there may be something improperly installed, or missing, from your setup. Are there any support brackets (from exhaust manifold to turbo downpipe) that are supposed to be present but missing in your application? I'm not too familiar with the vanagon TD exhaust setup but maybe someone else can chime in. I can imagine a big, heavy, unsupported exhasut system perhaps overloading the turbo mounting bolts. The exhaust system should probably be supported somehow. I know that on transverse mounted 1.6TD's, VW put a support bracket tieing together the exhaust manifold to the turbo downpipe, which would seem take some vibrational/cyclical load off of those turbo to exhaust manifold bolts.
Are you thread chasing and cleaning the threads and using copper-based anti-seize prior to bolt installation? Crap in the threads could result in less clamping force than clean, anti-seized threads. Copper-based anti-size is the only thing I've found that can stand up to the extreme temps these bolts see - I really doubt any kind of threadlock would work at those temps.
If all else fails, and you have access to safety-wire drilling jig and tool, stainless steel safety wire through the bolt head certainly sound like one way you could keep those bolts from backing out. It just sounds kind of weird that it would be necessary. Hope this helps! Good luck.
OK, so I've been road-testing my '91 Vanagon gas-to-TD conversion for a few days~150 miles. Found 3 of 4 bolts that hold turbo to exhaust manifold (Quantum TD) had worked loose, though I had torqued to spec in manual. Any suggestions on how to keep these tight? Best thing I can think of is to drill small holes and safety wire heads together.
Let me just ask you this out for curiosity: Did you notice any boost decrease because of that?
The factory vanagon TD downpipe has a heavy bracket that goes from just below the lower 2 turbo-DP bolt holes down to bolt holes in the block just above oil pan. So the bracket supports one end of turbo and DP.
Thats using the vanagon / quantum style TD exhaust mani / turbo setup.
Turbo didn't get so loose that it was leaking, at least not so I would notice. With engine at 50 degrees and turbo 'hanging' off manifold I decided early on to make custom struts to support the turbo. I used Vanagon 1.9 gas exhaust support tubes cut, welded and bent to fit. They bolt to hardware on either side of the exhaust turbine housing and extend down to connect to the block bosses at two spots, sort of triangulating the block, turbo and exhaust manifold. Have a Jetta TD downpipe temporarily with outlet 2 inches off pavement! Got my 2.5 inch mandrel bend kit so it's off into the shed tonight for more fun fabbin' the exhaust.
I think I'll replace those bolts with some higher grade, maybe 10.9 and just up the tightening torque a bit.