Tips for removing E30 exhaust?

Get a small bottle of rust-busting fluid and liberally apply it to all of the studs, lugs and nuts that you need to remove - and let that do its thing overnight. Then try loosening the nuts.

If you get to where you're sure you're about to break something, it's time to get out the propane torch to heat up the nut (obviously, using care not to light-up the car ;-)

Fire makes everything good :-)

/daytripper '00 s4 6spd

If none of this works and the stud does break off, remove the manifold from the side of the engine and put in a new stud. One of mine sheared off and after I removed the manifold (easy with the downpipes already off) I heated the area real good with a torch and spun it right out. The studs will most likely unscrew from the manifold at which point it's easy and cheap to put in new studs. I would have been alright but the one bolt was dicked up and I twisted the end of the bolt off with the nut still attached (impact wrench and a screw it attitude). Since I didn't care if I ripped the stud loose, I poured the impact wrench to the job...

I reckon you've just got to accept a stud or two will break and be prepared to replace them. And use brass nuts in the future...

Originals are sometimes also some form of corrosion resistant steel.

Yes - have an exhaust fitted and they invariably fit new cheap steel nuts laying up problems for the future.

True - but broken studs don't always come out easily.

Thanks for the advice so far. Another tip I got from a co-worker was that if I had no luck with PJ Blaster was to start up the car and let it run for a while to heat up the manifold, let it cool a bit and spray on more solvent.

I've tried this twice now and still no luck. Leaning into the cheater pipe extension on the breaker bar heavily and quite surprised I haven't broken anything yet. I've also purchased some wobble extensions for the socket wrench which have a tapered as opposed to a square end, giving me a little extra slop to get the socket on the nuts.

Having run the car again last night and sprayed on more Blaster, I will try once again. However, this weekend if I am still not making progress it will be very tempting to buy some metric impact sockets and lay into it with the air wrench.

Any more suggestions are welcome, and for the guys who broke studs and had to pull the manifolds, please fill me in a little bit since I know I am at risk for doing the same. I hate to make more work for myself and considering the tough time I am having with the pipes, I assume the manifold nuts and studs would be just as bad. Plenty of rust on them as well, although it looks like you can get to them straight on with normal extensions.

Thanks, Christopher

The head to manifold fixings don't normally corrode so much as their temperature is restricted to something closer to boiling water temperature.

With the manifold off a broken pipe fixing stud can usually be persuaded out quite easily by heating the manifold with a blowlamp.

Christopher,

I was a professional mechanic for over two decades. In that time I have seen more than a few stubborn exhaust fasteners. Some of the worst ones only responded to a combination of penetrating lubricant and carefully applied percussion waves generated by an pneumatic hammer with a small drift tool attached. The force being applied at a shallow angle to one of the faces of the nut. If the threads are not too badly fretted, the nut should spin off easily after being "broken loose" with the hammer/drift tool. Worst case scenerio, you can torch them off, drive out the remainder of the studs and "through-bolt" them when you reinstall.

Best of Luck

Homer

Bolts holding manifold to block don't seem to stick anything like downpipe bolts. Don't know why but I'll accept Dave's explanation for lack of anything scientific...

Oi. Mine was meant to be scientific. ;-) The manifold itself has little in the way of cooling and exhaust gasses can make parts of it reach very high temperatures. But the engine castings are basically restricted to coolant temp so the fixings at that end of the manifold will be kept cooler by conduction.

Actually the head is cooled or rather kept at a reasonable acceptable temperature - hopefully by the "cooling system" whereas the downpipe is where ALL the exhaust gasses meet and remember they are still expanding thus slowing and the heat remains there longer. If that area gets anywhere near "red hot" which it can easily do then you have an oxygenating situation. When anything burns it must combine with oxygen - when metal or rather steel (iron) burns if creates Ferrous Oxide that is commonly referred to as RUST. Eventually the rust or FeO2 expands and meets the other members of its clan on the flange, studs, washers or whatever might be about that contains Fe (iron).

When we used to do turbo conversions we always used Stainless studs and Aircraft locking stainless nuts (the type with the pinched washer type locking arrangements) DO NOT make the mistake of using Ny-Locks as the plastic WILL melt and the nuts fall off.

FORD downpipe nuts used to be made of BRONZE - albeit not high quality but bronze all the same which was a step in the right direction and these 17mm nuts were self locking too as were the studs that were, strangely, made to X-thread to lock into the manifold and or cyl heads.

Also remember that the downpipe connection is lower that the head flange thus susceptible to water splashes and condensation from short journeys where the temperature doesn't get high enough. Another thought is that unleaded fuel burns at a higher temperature than leaded and more vigorously so the temperature is naturally going to be hotter too.

Exhaust systems are usually aluminium coated these days and some are SS but not many. The exhaust is designed to run HOT to enable the cat to start working ASAP so high temps again at the downpipe (cats cause restrictions that slow the gas thus heat is held in place for longer). Hot exhausts mean less water vapour and cats mean less acids etc so we now have exhausts that last for ten years or more rather than the old days when they needed swapping every two years due to rust and acid eating through the silencers (mufflers).

The original cats and exhaust were as good as new when I sold my E38 740i two months ago - 13 years old with 198K miles.

There's my 2p or 2c worth but someone out there will disagree..................!

Alright guys, when I said "due to lack of anything scientific", I was being sarcastic. I certainly didn't want to work anyones brain this hard. Dave's explanation was more than acceptable.

SMILE!!!

This ain't working hard it's easy for me to remember such trivial things like Dave and his electronics and Oppenheimer and the Atom Bomb.............!

It's the boiling of an acceptable egg that I have difficulty with and that contraption called a Vacuum Cleaner........... So I got married again (13 years ago) Why buy a dog and bark yourself I say.....;>))

BTW my mate Spock said it only Logical........................... Live long and Prosper.

Meh. According to his sig, he probably copied someone else's work ;-)

Go away Daytripper.............. All my own work but then you could say that the information was learned or taught via a good education and practical skills which has been handed down through the ages from Archimedes to Major Carter of Stargate Command........................

It's all available in the physics books and chemistry books plus having the intelligence to put the information into practice. that why we have trainee Mechanics (Some never learn), Engineers and so forth such as Doctors etc....

No sir - you are never too old to learn something new and once learned it is usually never forgotten. Sometimes the brain will only remember the major points and you will have to return to the book to see which order the head bolts need tightening in and to what torque and similar fine details but once grasped the basics of a situation and the caused of problems one can usually use the transferable skills to tackle a similar situation and produce a reason (development engineers) and effect a remedy (Production engineers). However, there is no known solution to work done by the majority of owners and/or "quick-Lube" or " Kwik-Fit" depots and so called exhaust specialists.

At my age (61) I've done a lot of racing, building fast cars and race engines, power-boat engines and designed and fitted turbo-Chargers to production cars for a couple of major importers to the UK in the early days (80 - 85) when I decided to retire but got an offer I couldn't refuse - wife wanted a divorce..!!!!!!!!!!!!!!!!!!!!!!!

I now teach Electronics and Engineering to idiots that like to think of themselves as the world's best at the tender age of 16.

Thanks all for your suggestions. I was able to get the exhaust system off over the weekend and didn't break anything in the process.

There was no real secret to it other than perhaps persistance. Repeated soakings with PB Blaster, heating with a torch, and trying to break the nuts loose every night for a week, the nuts finally gave in. I'll also point out that these were steel nuts. When I put it all back together I will use copper or brass nuts and antiseize.

With those manifold connections undone, I simply disconnected all exhaust hangers, pipes supported with two floor jacks, and with some wiggling to get it loose, I was able to drop the entire exhaust system off in one piece and drag it out from under the car. Heat shields enclosing the tunnel were easy to remove.

My diagnosis was correct that the center bearing rubber mounting is completely destroyed. Everything is marked for proper reinstallation but I can't remove the driveshaft just yet. I need to get an offset wrench to get to the nuts on the forward side of the flexible coupling (guibo sp?) which looks just fine. Bentley manual shows an open end wrech reaching right up onto those nuts but my rear transmission mount is wider and in the way, possibly because my car is a convertible or the book is not showing the mount for an automatic trans, which I also have.

Should I run into more trouble I'll post again. Should all go well I might post an update just for whoever else tries this later.

Christopher

this is off and yet not off topic, hope nobody will mind the segue. i bought my 85 some months back, and just starting to get into its issues. one of which came to mind when seeing this thread...that is, need to replace the front brake rotors, and that silly little set screw just doesn't want to come out. i certainly haven't been as persistent as christopher; tried a couple of times letting it soak with liquid wrench, but with that little (5mm?) hex needed to get it out, can't exactly get out the breaker bar, so i'm not getting anyplace. so, on the related topic of getting stuck bits out, anyone have ideas for me here? (on the list for future are window switches, a sunroof that i have to crank manually, a non-functional ac that i sweated through this summer and hope to tackle over the winter, rear shock mounts and finding a replacement for that silly black cardboard cowling under the dash that keeps falling down and getting stuck on my feet or worse interfering with pedal operation entirely...still, brakes are a priority so i thought i'd get there first.)

thanks in advance.

? I thought SS exhausts were the norm.

Really only need to remove the three bolts holding the driveshaft yoke to the flex coupling. The three holding the coupling to the tranny can stay where they are...