SLIGHT fissure (crack) in the exhaust housing of turbo - is this bad?
12-05-2001, 05:42 PM
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SLIGHT fissure (crack) in the exhaust housing of turbo - is this bad?
<center><img src="http://a4toronto.homestead.com/files/crack.jpg"></center><p>how common is it? for those of you that have replaced a turbo, do you have the crack too?
here's the story - i found a replacement for my turbo. it's off a 98.5 with 59,000km on it. i examined it and found this crack. the pic makes it hard to see, but it's there. should i be worried?
it's hard to see in the pic, but it worries me a bit. it's quite prominent.
here's the story - i found a replacement for my turbo. it's off a 98.5 with 59,000km on it. i examined it and found this crack. the pic makes it hard to see, but it's there. should i be worried?
it's hard to see in the pic, but it worries me a bit. it's quite prominent.
12-05-2001, 05:52 PM
#4
Hmm....
Well, where the crack occured is a hot spot, as the exhaust gases flow slower there as the pressure drop is higher on the leading inside face of that bend. So, the crack is definately a heat related issue.... Also - the inside of the bend is where the maximum residual stresses are from the mandrel tube bending process of making the exhaust header. Another reason a crack would form there basically, although some will argue the hot exhaust gases acted like an annealing process and stress-relieved that area.
Is the crack all the way through? (doesn't look it) Can you tell how deep it is? Is it something that you could insert a polishing tip of an air grinder into? You may be able to grind the area down a bit, and have a good welder fill it in, and then have it re-ground with a fine bit and then polished. But, this will probably cost more money than if you were to just buy a used header at the junkyard where you got your turbo from.
Basically - it's a material defect, I'm sure lots of our cars have these and most will never know they ever existed.
My 2 cents.
Is the crack all the way through? (doesn't look it) Can you tell how deep it is? Is it something that you could insert a polishing tip of an air grinder into? You may be able to grind the area down a bit, and have a good welder fill it in, and then have it re-ground with a fine bit and then polished. But, this will probably cost more money than if you were to just buy a used header at the junkyard where you got your turbo from.
Basically - it's a material defect, I'm sure lots of our cars have these and most will never know they ever existed.
My 2 cents.
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12-05-2001, 06:29 PM
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bad idea on the welding....
...regardless of what type of welding you perform (MIG or TIG) this is a cast piece and you are almost guaranteed that exhaust heat will cause the bead to separate from the cast iron.
I'm not saying that it is impossible to notch it right and get a good bead in there but I wouldn't be too comfy when it got above 1500F. One little glowing red piece of projectile can wreak havoc on a turbine!
Mike O.
I'm not saying that it is impossible to notch it right and get a good bead in there but I wouldn't be too comfy when it got above 1500F. One little glowing red piece of projectile can wreak havoc on a turbine!
Mike O.