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Old 12-30-2011, 03:12 AM   #1
Drew@Swift Motorworks
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What I've Learned About Stuck Exhaust Bolts

Making this thread to pass along some information for anyone who wants to change their exhaust or runs into the kind of problems I did.

I did some work on a car that came from the East Coast, so with the weather and salted roads the nuts that hold the exhaust to the headers were crazy seized. I didnt have any problems on my own car, a California car its whole life, but I did deal with this on another California as well.

The parts in question are the studs and nuts that join the exhaust to the headers. The studs are flat backed and pressed into the header flange, so you dont have to hold a wrench on them when threading tightening the nut. While this can make life a bit easier on and ideal job, if youre nuts seize its going to make your life a lot harder. From what Ive read BMW tried to avoid seizing here by using stainless studs and copper nuts. It looks like sometimes that combination just wasnt good enough though and with heat cycling and exposure to the elements the nuts will seize on to the studs.

The first thing you should do before you tackle an exhaust swap is soak the nuts and studs in a penetrating lubricant like PB Blaster or WD-40 etc. Ideally you want this to soak in over night. If the nuts wont budge after soaking them you can try some other steps like the ones MKodama outlines in his excellent thread: http://forum.e46fanatics.com/showthread.php?t=864113

When all else fails youre either going to be left with studs that shear off right below the nut or nuts that youre going to have to cut off.

From this point on youre going to have to replace the stock studs and nuts. You can order new OEM studs and worry about pressing them in, but it would probably be a waste of time and money. You'll have to replace the studs with bolts and new nuts and to do that youre going to have to remove the remnants of the stock studs. Again there are several options here and which one you take will depend on your access to certain tools.

The easiest method to remove the stud is to heat the flange until it expands and you can hammer the stud out. However, a standard propane torch will not work for this, you simply cannot get it hot enough... Ive tried. You need to use and acetylene torch to heat it then smack it with a hammer or preferably an air chisel.

If you dont have access to these tools you should decide if its worth it to continue to diy or take it to a shop. From what Ive heard it is a quick 20 minute job at an exhaust shop and can cost anywhere from $20 to $50.

If you decide to diy youre going to spend close to an hour per stud to remove them. What youre going to have to do is drill the studs out.

I would advise leaving the stud sticking out past the flange instead of cutting it down till its flush with the flange. I originally thought that shorter would be better as there was less distance to drill, but if you leave it extended out past the flange it will make it easier to remove in the end.

Make sure you have a good, powerful drill with nice sharp bits. A corded drill might be best for the power and the weight behind it. When drilling metal you want to go at a slow speed and apply lots of pressure. Also, you need to use a lubricant for your drill bits. From what Ive read you can use a number of things for this, WD-40, motor oil, and even soap and water. You should spray on lubricant about every 10 seconds or so. WD-40 and soapy water are good for this... motor oil, not so much. Be sure to put a tray or catch can under the headers to catch run off lubricant and metal fillings. Protect yourself with eye protection and even respiratory protection, you dont want to inhale fumes from your drilling.

So start with a very small drill bit go at a slow speed and apply a lot of pressure. Once your first hole is drilled all the way through you can start stepping up each drill bit size until youve basically reached the diameter of the stud. Once the integrity of the sides of the stud are compromised and it no longer grips the flange you should be able to hammer them out. This is what it will look like when it pops out:



Unfortunately I made the mistake of cutting the studs down to the flange on 3 out of the 4 and I was unable to remove those, even with a punch and hammer. The only one I could remove was the one that I left long since I was able to hammer on the stud itself. This may not be sound advice, but if you cannot remove the stud then you should be able to just drill it wide enough to run a new bolt through the hole. It should end up looking like this:



Hopefully this will help someone out and save them some of the time that I wasted
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Old 12-30-2011, 08:24 AM   #2
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Yep, this was exactly what happened on my friend's E36. I was lucky (or maybe just more experienced) not to experience this on my own car. A couple tips of my own:

1) I've found that AeroKroil (http://www.kanolabs.com/) works significantly better than the OTC penetrating lubricants e.g. PB Blaster or Liquid Wrench. Quite important on jobs like these where the header studs are known to shear

2) Another method if the nuts still won't come off, or if you are shearing the studs, is to use the candle method. Essentially, you take a candle, heat up the nut on one side while you place the candle on the threads on the other side, and let capillary action draw the wax into the nut. It's a pretty old school method to release nuts from exhaust manifolds and such, but it works.

3) Also, if you decide to heat up the studs to pop them out, be mindful of the O2 sensor that is right upstream of the studs. It wouldn't be a bad idea to remove it altogether to avoid damaging it.

4) If you do shear it, take it to a muffler shop to have it hammered out. It really isn't worth the time to drill the studs out (although there were 6 on the E36 as opposed to what looks like 4 on the E46) when you're upside-down under a car...it sucks.

5) If you shear the studs, replace them with bolts. It will make your life a lot easier if it shears again the next time you remove it.
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Old 12-30-2011, 09:22 AM   #3
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or just get a plumbers torch, hold it on any rusted nuts for a while 1-2 minutes, the nut expands and will then turn off much easier and save you the headache of all that other mess.
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Old 12-30-2011, 09:44 AM   #4
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4 years when I replaced my engine I also replaced the copper nuts, with new ones from BMW. A few months ago while removing the exhaust, the nuts were in top shape but not the studs. One of them snapped at the surface level of the flange. I just drilled it through as per OP method and replaced with a stainless steel bolt/nut.
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Old 12-30-2011, 11:02 AM   #5
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Where the hell was this thread in July. I ended up sawing my exhaust off in a fit of inspiration only to find it didn't help. I ran only a down pipe for a week till I could go to a muffler shop. WD-40 is a child compared to PB blaster, and I didn't even know about it at the time or AeroKrpil so thank you for helping peeps like me in the future
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Old 12-30-2011, 11:12 AM   #6
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This is great advice, except for the part about trying to bang the studs out from the nut side. I did read somewhere that banging too hard on that flange can actually damage the internals of the post-cat O2 sensors. Not sure how true that is, but as I had just replaced my O2 sensors and had to encounter this, I was extra careful. I had to do this TWICE, the first time I put on my UUC TSE3, and the second time I had to remove it and put it back on again to replace that section as it was leaking. Fully covered under UUC's amazing warranty, but man, those 4 bolts are my LEAST favorite thing on the entire car. Horrific.
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Old 12-30-2011, 11:15 AM   #7
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Quote:
Originally Posted by trizzuth View Post
This is great advice, except for the part about trying to bang the studs out from the nut side. I did read somewhere that banging too hard on that flange can actually damage the internals of the post-cat O2 sensors. Not sure how true that is, but as I had just replaced my O2 sensors and had to encounter this, I was extra careful. I had to do this TWICE, the first time I put on my UUC TSE3, and the second time I had to remove it and put it back on again to replace that section as it was leaking. Fully covered under UUC's amazing warranty, but man, those 4 bolts are my LEAST favorite thing on the entire car. Horrific.
Banging on them also puts stress on your head , i know people who've cracked their heads when their headers hit the ground(lowest point on the car)....

Best way would be to remove headers and use a vice/hydraulic press.

Or replace the bolts every 2 years...
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Old 12-30-2011, 11:42 AM   #8
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PB Blaster
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Old 12-30-2011, 12:37 PM   #9
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Quote:
Originally Posted by dreamdrivedrift View Post
Yep, this was exactly what happened on my friend's E36. I was lucky (or maybe just more experienced) not to experience this on my own car. A couple tips of my own:

1) I've found that AeroKroil (http://www.kanolabs.com/) works significantly better than the OTC penetrating lubricants e.g. PB Blaster or Liquid Wrench. Quite important on jobs like these where the header studs are known to shear

2) Another method if the nuts still won't come off, or if you are shearing the studs, is to use the candle method. Essentially, you take a candle, heat up the nut on one side while you place the candle on the threads on the other side, and let capillary action draw the wax into the nut. It's a pretty old school method to release nuts from exhaust manifolds and such, but it works.

3) Also, if you decide to heat up the studs to pop them out, be mindful of the O2 sensor that is right upstream of the studs. It wouldn't be a bad idea to remove it altogether to avoid damaging it.

4) If you do shear it, take it to a muffler shop to have it hammered out. It really isn't worth the time to drill the studs out (although there were 6 on the E36 as opposed to what looks like 4 on the E46) when you're upside-down under a car...it sucks.

5) If you shear the studs, replace them with bolts. It will make your life a lot easier if it shears again the next time you remove it.
Thanks for that added info. That candle method seems archaic... but id definitely try it

Good point on 3... I didnt mention anything, but I assumed people would be smart enough to avoid hitting the O2 sensors with the heat.

As per 4, yes a shop would be way easier... But Im just trying to put out every option and tell people what I did.

Quote:
Originally Posted by vI6ious View Post
or just get a plumbers torch, hold it on any rusted nuts for a while 1-2 minutes, the nut expands and will then turn off much easier and save you the headache of all that other mess.
Yes, Thats covered in the Mkodama thread that I mentioned... unfortunately that doesnt always work.

Quote:
Originally Posted by paraklas View Post
4 years when I replaced my engine I also replaced the copper nuts, with new ones from BMW. A few months ago while removing the exhaust, the nuts were in top shape but not the studs. One of them snapped at the surface level of the flange. I just drilled it through as per OP method and replaced with a stainless steel bolt/nut.
Yep Ive done exhausts on 4 cars and had sheared studs on 2 of the 4

Quote:
Originally Posted by Dirty Mike View Post
Where the hell was this thread in July. I ended up sawing my exhaust off in a fit of inspiration only to find it didn't help. I ran only a down pipe for a week till I could go to a muffler shop. WD-40 is a child compared to PB blaster, and I didn't even know about it at the time or AeroKrpil so thank you for helping peeps like me in the future
I didnt know about AeroKrpil... Ill definitely have to get some of that

Quote:
Originally Posted by trizzuth View Post
This is great advice, except for the part about trying to bang the studs out from the nut side. I did read somewhere that banging too hard on that flange can actually damage the internals of the post-cat O2 sensors. Not sure how true that is, but as I had just replaced my O2 sensors and had to encounter this, I was extra careful. I had to do this TWICE, the first time I put on my UUC TSE3, and the second time I had to remove it and put it back on again to replace that section as it was leaking. Fully covered under UUC's amazing warranty, but man, those 4 bolts are my LEAST favorite thing on the entire car. Horrific.
Thats a good consideration. I hadnt heard that about the O2 sensors, but maybe just removing them would be a good solution.

Quote:
Originally Posted by Pir4t View Post
Banging on them also puts stress on your head , i know people who've cracked their heads when their headers hit the ground(lowest point on the car)....

Best way would be to remove headers and use a vice/hydraulic press.

Or replace the bolts every 2 years...
Yeah but then the headers have to come out... which is an even longer job then drilling. Im really not convinced that smacking the end of the flange with a hammer puts enough stress on the head to crack it either... There would be so much more force on it with a moving car impacting the road. One thing you could do though is brace the flange with something like the head of a sledge or a breaker bar. You should be able to brace it between the flange and the subframe reinforcement plate, but you probably need a second person for that.

Quote:
Originally Posted by ac_2007 View Post
PB Blaster
No.
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Old 12-30-2011, 12:39 PM   #10
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yep, removing O2 sensors near that flange would definitely be best, even leaving them connected, but not attached to the exhaust bung.. that's too much of an expensive part to risk destroying over a few hammer bangs!
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Old 12-30-2011, 12:47 PM   #11
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yep, removing O2 sensors near that flange would definitely be best, even leaving them connected, but not attached to the exhaust bung.. that's too much of an expensive part to risk destroying over a few hammer bangs!
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Old 12-30-2011, 12:53 PM   #12
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I just removed the studs from my manifolds but off the car. Using my hydraulic press, they needed about 3-4 tons of pressure before they pop put (compared to most suspension bushes needing 1-2 tons). I used a 16 mm socket under the 'head' of the stud for support, otherwise the flange would bend.
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Old 12-30-2011, 12:57 PM   #13
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No.
Worked wonders for me

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Old 12-30-2011, 07:06 PM   #14
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I just removed the studs from my manifolds but off the car. Using my hydraulic press, they needed about 3-4 tons of pressure before they pop put (compared to most suspension bushes needing 1-2 tons). I used a 16 mm socket under the 'head' of the stud for support, otherwise the flange would bend.
that's a lot of force. That's definitely the more thorough method... That's just a lot of work and extra equipment

Quote:
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As I mentioned that's a great early option. But the intention of this thread was to share some strategies for removing the nuts if PB Blaster isnt cutting it.

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Old 12-30-2011, 07:19 PM   #15
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Old 12-31-2011, 05:11 PM   #16
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or just get a plumbers torch, hold it on any rusted nuts for a while 1-2 minutes, the nut expands and will then turn off much easier and save you the headache of all that other mess.
Usually doesn't work with the header studs unless you use MAPP or acetylene

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I didnt know about AeroKrpil... Ill definitely have to get some of that
They have a Google deal...$12 + 6 shipping for 2 king size cans

http://www.kanolabs.com/google/
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Old 07-19-2012, 09:52 AM   #17
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Bringing back an old thread, But I am stuck after cutting off the exhaust bolts on my E46, and this seems like the only relevant place.

Anyway, after TONS of penetrating lubricant, heat, chisels, hammers, and finally cutting the bolts clean off... you would think that the exhaust pipes would release from the header flange? NopeÖ The thing still wonít budge; itís locked in place as if the bolts are still there, because of massive rust.

I'm looking for information on where I can go from here. Once I can release the pipes from the flange connection, Iíll go with the drill out method discussed above for the remaining bolts:

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Old 07-19-2012, 11:46 AM   #18
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I would think actually staring and driving the car would heat and loosen things up.

You could also try to carefully wedge something between the flanges and use leverage to set them apart.
If not, take it to a shop so you don't do more damage.
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Old 07-19-2012, 11:54 AM   #19
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The shop that I brought mine to had to use an impact hammer with a pointy bit to get them out. Heat didn't work for mine either.

Good luck.
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Old 09-04-2013, 12:30 PM   #20
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Hey guys.

I have an E60 545i that I'm slowing fixing/rebuilding.. bit of a project (autobox, water leak, etc.)

A couple of my manifold/downpipe-> midpipe studs sheard off (note that I have been able to remove the exhaust and midpipes - it's just that I have sheared-off studs left exposed. Obviously this won't help you guys who can't actually unbolt and remove the midpipes.)

Anyway I wanted to share the puller contraption that I have put together that I am *hoping* will do the trick for pushing them out.

It's a harmonic balancer/damper puller, combined with the metal tuning-fork-like piece from a steering wheel puller. The steering wheel puller has a hole in the middle that's nicely big enough for the head of the stud to pass through.

I guess basically doubling-up any sort of puller should do the trick really.

Anyway here's pictures of what I've just put together on the bench. I'll let you know if it works. I might try it this weekend. I have a new replacement stud there in the pictures ("knurled bolt 18407536175") just to see that it fits through, and it does. I might actually replace the broken studs with regular bolts.

puller for cat to exhaust studs e60 545i

puller for cat to exhaust studs e60 545i

puller for cat to exhaust studs e60 545i

puller for cat to exhaust studs e60 545i

This is the first time I've used flickr. If the images don't show, you can try this link:
http://www.flickr.com/photos/101357271@N08/9671307175/

Hope it (the puller, and the pics!) works!
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