Exhaust Bolts Rusted...

[Nick Calne]

My exhaust header bolts are so rusted that they are totally round and un-removable.
Normally I'd just cut something like this off and replace it.

But given the studs that go into the head are actually as bad, I'm a bit worried and doing this.

any thoughts....before I fire up the angle grinder.....?

[Mustang]

good penetrating oil and an air impact gun just might spin the studs right out of the aluminum block and then just replace the studs and nuts but use 'Loctite never seize' on them when you reassemble

[Dr. Mordo]

I'd hose them with lube, hammer a smaller socket on them, and use an air gun.  I'd bet you can get these off with if you fight for it.

I might then try drilling a hole thru the nut and bolt and sticking a rod (or maybe a screwdriver?) thru it so I could get some torque.

If you cut them off, it'll be a pair of vice grips clamped as tight as they'll go trying to fight the studs out, which sucks.

[Ocelotl]

Good advice above. I used part number  96334-0VGA  bolt extractor sockets from Harborfreight.com to remove subborn, rounded off nuts before, they worked great.  Work them out (back and forth, lots penetrating oil) slowly or you may risk snapping off the stud--not fun extracting those. Don't ask me how I know. That's why the air impact tool thing would come in handy. Yeah, change the studs if they look knackered. 94640-9VGA looks like a good tool for extracting the studs especially once the header is off, but putting two nuts on the stud, tightening them against each other and then putting a wrench to the inner nut to extract the stud works just fine.

If you do decide to cut off the nut, get a small enough grinder or cutter to split one of the nut's sides instead of lopping off the stud.

[Stretch]

A nut splitter works, if there's room to get it in there...



http://www.northerntool.com/webapp/wcs/ ... 4573_34573

[Sin_Tiger]

I have a set of those, sad to say most of the time they are useless. There's rarely enough space to get them on and mostly nuts do not rust parallel so they just slip off as you tighten them.

Heat is the answer but be patient and let it cool down before you try loosening the nuts or you'll just end up with a big chewed up mess or sheared studs.

Don't worry about the studs, if the nuts are in that state you need to renew the studs too. When you manage to get the old nuts off, assuming you have access to or can borrow a welder, push the next size nut over the end of the thread then weld the nut onto the stud. Let it cool down then try extracting the stud, you will have a bigger new nut to  exert better torque on and hopefully the heat cycle from welding will have been enough to help loosen them. A sharp blow on the end of the stud often helps start things off.

[nightrunner]

Kroil or Liquid Wrench are the good rust penetrants.   Supposedly there was a test in Popular Mechanics which found that 50/50 mix of ATF and acetone worked even better.  There's a thread on Advrider in the Wrenching forum.  If you have time, let them seep in for days and apply repeatedly.

I would use an impact driver rather than an impact wrench.  The driver will give you more control.   Another trick would be to use a Dremel with cutter wheels to cut just the nut while preserving the stud (for later removal).

Also use lots of penetrant when removing the studs.  Steel is harder than aluminum.  If a stud breaks, it will be a nightmare using easy-outs on a steel bolt in aluminum threads.

Good luck

[Nick Calne]

Thanks for the advice guys.  To add a little more detail.. the bolts are so rusty that when I touched them at first, they partially disintegrated into flakes.  Which makes a problem in getting anything like a socket to bite on them.  I guess there is a whole bunch of slightly dissimilar metals in that area and the exposed ones feel to pieces.  Think I will try a combination of methods when the weather and nights draw in a bit more.  Welding something useful on looks favourite at the minute.

[Sin_Tiger]

Another "method" I have used quite successfully on nuts like these where I wanted to save the stud was this.

Use a grinder dremel or file or whatever on two of the most convenient opposing sides, it doesn't matter if there is flat there already or not, and make two opposite flats by removing materiel until the thread is just exposed. You should just see one fine dark line of each thread at this point, two lines and you have gone too far and are eating into the stud thread.

Heat, cool penetrate and leave before trying to move the nut using a close size of spanner or an adjustable. One of two things will happen, the remains of the nut will start to turn due to it expanding slightly at the very thin flats or it will simply break into two pieces, either way job done.

This technique requires a lot of patience and hence is very time consuming.

It often helps not to try to turn nuts / studs out by rotating anticlockwise only, work them back and forwards while applying more penetrant, this helps to break the rust in the threads up into smaller dust particles which can be washed out of the now increasing clearances by the penetrant.

In a lot of cases I actually tighten stubborn nuts and bolts that are to be discarded before I try to undo them, this streches them a little more creating that important clearance. Be very cautious with that technique with studs, particularly if they are into alluminium.

If the worst happens, don't panic there is always helicoil which will leave you with a stronger fastening but of course is more time and money.