My 2001 525i started making a bit of unauthorized exhaust noise a week or two ago. Fast forward to this past weekend, when the noise became considerably more intolerable rather suddenly. I investigated and discovered that one of the two flange gaskets connecting the header pipes to the main exhaust had blown out. This would not be a major problem (2-bolt flanges, fairly accessible), except that the nuts and bolts (or perhaps studs - I'm not sure) are completely and totally rusted, as in you can no longer visually determine what they once were. On top of that, one of the flange holes has disintegrated on the outer rim. I need to get this repaired with as little aggravation as possible. The problems are 1) bolts/studs are useless and stuck in the header flanges - these must be removed and replaced, and 2) at least one flange is shot and will probably prevent proper sealing, and thus also needs to be replaced.
I'm considering just cutting off the flanges and replacing with split flanges such as these: Split flanges.
Anyone have experience with these? Other suggestions to keep me from descending rapidly into madness?
I would cut the flanges off, weld a small piece of tubing on to make it a slip joint, and clamp it (or weld it)
Blast em out with the smoke wrench, nut n bolt, lots of permatex ultra copper (don't bother with a gasket). Split flange should work if you really need it, just leave what's left of the old flange in place, they don't grab the pipe.
Thanks. I like the slip joint idea, but I'm not sure if it will work in this particular situation due to the shape of the pipes (and my pathetic welding skills). I can't just weld the whole thing in place, as the system needs to be removable in the event of driveline repairs, and the thing is basically one piece from this joint back.
Good advice about the split flanges not grabbing the pipe. I was anticipating that they would, but then I have no idea if the pipe is flared under the flange or not. The rust is bad, bad enough that I wonder if even a torch will loosen it. I'm anticipating a bunch of angle grinder action (ugh...).
The least trouble I've had with this situation is these:
Walker flanges
You can just ignore the stock flanges, and put one of these just outside each of them on the pipe, using bolts long enough to bridge the gap. Only tool I need is a wrench.
Interesting. What is it about the Walker flanges that makes them preferable to the other ones? They're obviously a very different style, but is there something about the design that makes them easier to work with in this sort of situation?
EDIT: OK, looking closer I think I see the benefit. The Walker type can be tightened down on the pipe itself, while the other ones just rest against whatever's there (pipe, old flange, etc.). Probably worth getting the Walker pieces, given the state of things under there.
I have no advise other than to point out that if those bolts are like the M3 ones, they are Inconel and therefore a major pita to cut. If you dont have an air hammer, I would bring it to a muffler shop and have them cut them off.
The replacement bolts are $$$ as well.
Slippery wrote:
I have no advise other than to point out that if those bolts are like the M3 ones, they are Inconel and therefore a major pita to cut. If you dont have an air hammer, I would bring it to a muffler shop and have them cut them off.
The replacement bolts are $$$ as well.
I don't know what they are (or more accurately, were), but I was able to get through one with a Dremel fairly easily, so I don't think it's going to be a major issue, especially if I'm not trying to preserve anything. At this point I'm think four new flanges oriented 90 degrees from the originals and done.
I'm following along, as our minivan flex pipe will require a similar repair in the near future.
