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Old 10-20-2013, 02:36 PM   #57
AdmiralSenn
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Join Date: Jan 2007
Location: Vero Beach
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CBV is not leaking. Wastegate actuator is holding pressure as well. I also tested the entire pipe system from the intercooler to the pipe out of the compressor, which holds pressure all day long, and I tested going the other way (intercooler to throttle body) which also holds.

The leak is somewhere between the AMM -> turbo hose (brand new silicone) and the compressor outlet (also attached to brand new silicone). Basically it's as close to testing just the turbo housing itself as is possible. Here's the setup:

Line from compressor -> inflation attachment -> 'test cap' plug replacing AMM -> silicone elbow -> turbo inlet -> turbo outlet -> silicone joiner -> solid test plug.

I ditched the original cobbled-together hoses and everything from the turbo to the intercooler is new aluminum hard pipes with silicone joiners and adapters.

I don't see any cracks on the housing but I'm leaning towards something of that nature. I also can't easily check underneath because a friend has my jackstands and ramps.

Symptoms now are nearly perfect driveability, minus boost power when hot. I can stomp on the gas pedal and get no more backfires or struggling. Boost comes on hard when dead cold, then rapidly falls off as the engine warms. Boost gauge still shows pressure and responds to MBC adjustments but the power, while better than before, is still not up to par. Occasionally I will get a pull that feels like about 50% boost but I haven't found anything to explain why. When this happens, the 'felt' acceleration doesn't kick in until much later than usual.

All things point to something that gets worse with heat (e.g. cracked housing), and I can hear air whooshing through SOMETHING on the turbo when I leak test it, but I can't feel any air leaks. I wet my hand and ran it all around the compressor housing, but I can't feel anything. Previously I confirmed a leak this way when I could feel the air escaping from the wastegate actuator.

I'm wondering if it's possible for the turbo to be leaking internally somehow, but I don't have the faintest idea where it could be leaking. The shaft exhibits almost no play on either axis, it's like it's brand new.

The only other thing I can think of is that the silicone fitting on the outlet is supposed to be straight, but it's bent a little for clearance. I feel no leaks there, though, and the clamp on it is very tight. I've ordered a new 30 degree one just to be sure (also will help line up the piping a bit better) but I don't think that's it. I hope I'm wrong, of course.
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