exhaust system sort-of upgrade

[BennyM]

Hey everyone. I got a used exhaust system (everything but the cat) to replace my holy (not in the religious way) mufflers and pipes on the cheap (cheap being a key word here).

I've assembled a list of new bolts, gaskets, and hangers to order, but since I've never done any exhaust work before, I'm unsure about how much of the work I can really do myself and what the proper workflow should be. I know the old exhaust system is going to be a pain to take off, and what's even more complicated is that I want to keep the same catalytic converter and use it with the newer rust-free pieces. It looks like one side of the cat needs to be cut and welded while the other side will just bolt onto the center silencer. So, can I get away with having a shop do the cut and weld while I do the rest of the hanging? i'd really appreciate some advice from those of you who have tackled this before.

As always, thanks in advance.
BennyM

[whiskychaser]

If the 'new system' came from a 525i then I dont see why you would want to cut anything. Its 'just' a nuts and bolts job - albeit rusty old nuts and bolts. I dont understand why you cant leave the leave the 'old' cat where it is and just bolt the rest onto it. I must be missing something really obvious here. :)

[BennyM]

You're right. I should have clarified that I also need to replace the pipes that connect the headers to the cat. These are the pipes that meet where the 02 sensor plugs in. From what I can tell, that is not a simple unbolt/rebolt operation.

I was also hoping for some general tips and tricks on how to make the exhaust removal go as smoothly as possible.

BennyM


If the 'new system' came from a 525i then I dont see why you would want to cut anything. Its 'just' a nuts and bolts job - albeit rusty old nuts and bolts. I dont understand why you cant leave the leave the 'old' cat where it is and just bolt the rest onto it. I must be missing something really obvious here. :)

[whiskychaser]

You're right. I should have clarified that I also need to replace the pipes that connect the headers to the cat. These are the pipes that meet where the 02 sensor plugs in. From what I can tell, that is not a simple unbolt/rebolt operation.

I was also hoping for some general tips and tricks on how to make the exhaust removal go as smoothly as possible.

BennyM
You are dropping the whole system so here's how I've done it:
Raise front of car and support on stands. Put a trolley jack under the sump guard to take the weight, then remove it noting position of stepped washers. Put a dab of grease on them so they stay in place when you come to put the guard back. Take off the right front wheel so it doesnt get in your way. Take off the lower heat shield. (Mine is RHD so you may not have this anyway) Two screws are visible but there is a (third) sneaky one - you put a socket on an extension up through a hole in the x member to get at it. Remove the 6 nuts that secure the downpipes to the manifolds. You will need a couple of extensions to reach them. Remove the nuts/bolts that secure the exhaust to the gearbox. Wiggle the exhaust to get the front to ensure it is free (easier said).
Put a trolley jack under the mid section and raise it a tiny bit to take the weight. The hangers on the back box clamp onto the seam (on mine). The one nearest the wing is a pita to get to but I can just manage it with a 3/8 extension. That just leaves the two rubber hangers. A bit of washing up liquid and gentle use of a screwdriver will make life easier!
Lower the whole lot and drag it out.
Not sure how the welder is going to make sure the angles are right on the pipes for the cat but HTH