Job time for removing cats...

[Lion Heart]

Hi guys

I need to remove my catalytic converters (downpipes) on my B7 S4.

I'm going to be doing it myself and do not have a ramp (jacks and axle stands only).

I've looked at the job in the Audi workshop software and looks ok. A few components in the engine bay to disconnect, undo driveshaft, drop subframe 50mm etc. Nothing that looks too scary.

But what I'd really like to know (from someone who has done it) is how long does it take???

[jmcS4]

First of all do you have a manual or tip???

if you have a manual then you're in much better shape than removing downpipes from a tip car.

get the car on stands and get as much clearance as you SAFELY can. you DO NOT need to remove the driveshaft at all. you do need to remove the CV axle shields to get enough room to pull the DP's out.

BE CAREFUL removing the O2 sensors!!! i suggest removing them prior to removing the DP's since knocking them around can damage them and you WILL throw a code, get horrible MPG and the car will not run very well.

Otherwise you'll need a couple long extensions and and a swivel socket to easily remove 6 nuts (3 on each downpipe) that attach to the manifolds. careful not to bend the flex pipe to much, my first time doing this job the flex pipe ripped clean in half but they were old and brittle.

also buy a very long spade drill bit or something similar to drill out the cats. if you're doing all four then it doesn't matter how you do drill them out. if you're just doing the pre cats be careful not to let the dust and bits fall into the larger main cat as it will clog it up and you'll be pulling them right back out


good luck. it can be done in an afternoon if you're mechanically incline!

[q_dubz]

i did it in like 2hours, so chop chop!

[Lion Heart]

OMG. 5 hours in and it's a NIGHTMARE.

I've removed ONE bolt from ONE downpipe, the outer most (easiest!) one.

I think I'll just about be able to get the top one, but the inner one has something next to it and will probably require a long bit and will be a nightmare (if actually possible).

And as for getting them back on - that will be even harder!!!

Two hours?????? Are you sure you were working on an S4 :-)

Absolute NIGHTMARE.

Can you give me some tips for getting these bolts removed.

The outer most bolt I accessed with a flexi head bit up from under the wheel arch in at an angle. They're damned tight too, just to make it even harder!

I'm struggling to get the odd angle, hold the socket on the bolt and undo it. Needed a second pair of hands whilst I held the socket to the bolt with my arm half way up the car.

Looking at it, I'm seriously not even sure that this is physically possible on the Tiptronic???!?!?!!?!??

Help me out guys - I must be doing something very wrong here if it's a two hour job?????

HELP PLEASE!!!

[q_dubz]

LONG ASS EXTENSION to get to the bolts from past the primary cat. Otherwise use 1/4inch drive rachet and 6in extension with a universal joint

As far as gutting the cats. You need a long like 12in cement drill bit and a small pry bar.

[Hooblah]

I do all of my work at the side of the road with axle stands. If I can do it in 5 hours I'm sure it can't be that bad!
The trickiest bit for me was getting the driveshaft heat shield bolts off from the gearbox. Lucky I had a tiny 1/4" wera socket set or I don't think I'd have managed!

So the downpipe bolts will need a long extension or two, and a swivel. I managed to gun one or two of them which made it easier.

I hope you have enough height to allow the downpipe to pull out, you have to twist it all over the place to get it out.

I used a SDS drill with the biggest bit I could find. Knocked it out in no time.

I also broke a flexi and ended up welding two new ones in (also at the side of the road lol). It did sound badass though with the exhaust off. I actually took it for a drive like that one night and the sheer rawness scared the living shit out of this this guy walking along the pavement! I was so amazed I creamed myself 😂

[Lion Heart]

The issue I'm finding is the angle. I have loads of extensions including xtra long ones. But the bolt cannot be accessed straight on.

It's almost as though I have to use two universal swivel joints, one to get the angle into the nut, and the second to straighten it back up, but then it's all really floppy and you have no control. I can hold the socket on to the nut, but then can't let go and so can't actually adjust and grab the wrench etc.

DId you get all three (each side) staright up from below, or at an angle in through the wheel arch?

The one that REALLY worries me in the innermost nut as that is squashed in against something (can't see it, only feel it!) - maybe side of gearbox? And the angle coming in from the side wheel arch looks impossible to get, and it seems to be impossible (?) to access at all straight on.

Was your experience on the tiptronic or the manual? I kow the manual box is quite a bit smaller and so access bound to be a lot better.

Any help with regards to the best angle of attack, and exact tools used most welcome!!

Thanks guys

[roboto_1337]

The issue I'm finding is the angle. I have loads of extensions including xtra long ones. But the bolt cannot be accessed straight on.

It's almost as though I have to use two universal swivel joints, one to get the angle into the nut, and the second to straighten it back up, but then it's all really floppy and you have no control. I can hold the socket on to the nut, but then can't let go and so can't actually adjust and grab the wrench etc.

DId you get all three (each side) staright up from below, or at an angle in through the wheel arch?

The one that REALLY worries me in the innermost nut as that is squashed in against something (can't see it, only feel it!) - maybe side of gearbox? And the angle coming in from the side wheel arch looks impossible to get, and it seems to be impossible (?) to access at all straight on.

Was your experience on the tiptronic or the manual? I kow the manual box is quite a bit smaller and so access bound to be a lot better.

Any help with regards to the best angle of attack, and exact tools used most welcome!!

Thanks guys

I got the driver's side ones straight on... top on that side was the hardest... the passenger side I went through the wheel passage.

[Lion Heart]

Hey roboto_1337

Thanks for that. Was yours an auto also?

When you say drivers/passenger side - UK or USA?

Also, what tool combo did you use? Could you attack any straight-on, or did you have to use one/two universal swivels to get odd angles?

And the million dollar question: are they harder or easier to get those nuts back on than they are to remove??

[apena1371]

Hey roboto_1337

Thanks for that. Was yours an auto also?

When you say drivers/passenger side - UK or USA?

Also, what tool combo did you use? Could you attack any straight-on, or did you have to use one/two universal swivels to get odd angles?

And the million dollar question: are they harder or easier to get those nuts back on than they are to remove??

It took me a total of approximately 7 hrs for removal, gutting and install. The install was WAY easier and faster than the removal. But I have a manual not tip.

[Lion Heart]

Yes, I can see 7 hours in it to be honest, and probably a bit more for the tiptronic auto!!!

I can't touch mine again until Tuesday/Wednesday. I think I'm going to attack the inner-most nut first as that seems hardest, and if I can't get that one the others are pointless.

Would be easier with a ramp for sure. NOt a lot of wiggle room working under an S4!!!

[roboto_1337]

Hey roboto_1337

Thanks for that. Was yours an auto also?

When you say drivers/passenger side - UK or USA?

Also, what tool combo did you use? Could you attack any straight-on, or did you have to use one/two universal swivels to get odd angles?

And the million dollar question: are they harder or easier to get those nuts back on than they are to remove??

No it's 6M, I didnt' have to drop the sub-frame.

Really I just played with different swivels/wobble extensions drive sizes long/short sockets until I found something I could get a good position/torque with. 5 of 6 were easy to get back on... the top nut on the driver side was the biggest pain... also when you put the axle guards back on I only did the 2 easy ones, so future work is easier.

a couple of things that i learned will make it go quicker... make sure you loosen the rear O2 sensors first, then drop the cat-back, and take them off the mid/rear hangers otherwise they'll stretch and the hanger with ting against the driveshaft... very annoying.

also the passenger side harness for the O2 sensors in the engine bay are easier to work with if you take them off and line them back up after.... driver side it didn't make much of a difference.

when pulling the downpipes out you also have to rotate them to work the bends around the axles/transmission.

I'm in Canada, so North American Left hand drive vehicle.

gutting them is easy I just used a 3/4"x 16" long spade bit and some long needle nose pliers drilled a bunch of holes and it comes right out.

*Edit* the nut that you feel is squished against something is a heat sheild for the exhaust manifold I beilieve, that's what makes the top nut an absolute bitch to get at, If I can remember a I got it off with an impact swivel socket and 2 extensions.. I wanna say 3" and 12" but can't remmeber for cetain.

Also don't quote me, as you may not have to do this, but I believe with the Tip you have to lower the sub-frame a little bit by using a jack and a wood block to give yourself a bit more room

[Lion Heart]

Thanks roboto_1337 - really appreciate the details!

[Lion Heart]

Worried now....

I just checked Elsawin and is shows that you do not disconnect the prop shaft on the manula and can drop the sub frame 60mm with it in place.

However, for the auto it instructs to disconnect the propshaft and to then drop the subframe 50mm.

Mine only went to 40mm and then stopped. But I did not disconnect the Propshaft as people here on this forum said not to. Good advice for the manual, but I'm thinking maybe very bad advice for an auto??

I basically put the entire engine and gearbox leaning weight on to that joint and its the joint inside the end of the gearbox that cannot travel further (the joint on the propshaft itself is fine, this is the part that exits the gearbox itself before attaching to the propshaft). Worried that the joint inside the gearbox itself may be screwed (bent) with all that weight on it at its maximum point of movement.

The car's not going to be back together for a while as sending my cats away for repair so I'm looking at a week or two beofre back on the road, but now worried when it's all back together that if I've bent something I'm pretty screwed :-(

Hopefully they're very strong?

[roboto_1337]

http://workshop-manuals.com/audi/s4/...ing/page_3751/

Just found this... it may be helpful. disconnecting the propshaft doesn't seem like a big deal if you have the proper tools.

I wouldn't want to keep any undue strain on the drivetrain for an extended period of time.

[Lion Heart]

Yes, disconnecting the prop shaft isn't too bad. I've done it before actuially.

It can be a PITA if the top most of the six bolts or is it 8, can't remember now) is right at the top (12 o clock) as then you usually need to rotate it a bit which you need to roll the car to do. So wheels back on, jack down, roll, jack up, wheels off again etc.

Also, breaking the seal once the bolts are out can be a pig! Lots of pulling and pushing and assistance from a rubber mallet.

I noted from the advice here that it is not required to disconnect the prop shaft - great I thought, that will save some time and an awkward job, but in retrospect I think that only applies to the manual (hence differing Elsawin instructions for auto and manual).

Yes, ageed putting undue strain on the running gear is not good. Hence I'm worried now (genuinely!)

I should have just went with Elsawin to start with, but you often get useful time-saving work-arounds. If I'd seen that manual and auto were different I definitely would have. But I only looked at auto before starting, and then noted I could only get 40mm and not 50mm, then noted at end of job gearbox exiting shaft at full bend (it appears at least, it's inside a rubber gaitor).

Hopefully will be fine.

[roboto_1337]

I'm still not convinced that 1cm would make that much of a difference, the fact that you're less than the 50mm should be to your benefit. Either way best of luck, I hope that nothing's warped.

[Lion Heart]

Yes, but the reason I could not get to 50mm is because the propshaft/gearbox connection fully locked at 40mm.

I went beyond the 40mm trying to get 50mm, and worked for a couple of hours in that position. In retrospect the leaning weight of the engine and box was directly on that joint.

And, as mentioned, its the section exiting the gearbox that cannot give any more angle, not the propshaft joint.