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This is the flange plate on one of my catalytic converters AKA exhaust manifolds where it joins the exhaust pipe.

enter image description here

enter image description here

Before they broke off, the studs looked something like this, the driver head was reverse torx:

enter image description here

The location of the flange is on the very underside of the vehicle with high exposure to water so no wonder it and the studs were badly rusted. I wanted to remove the two studs but the rusting/adhesion was so bad that they broke. First tried the proper method using a reverse torx socket, that broke off, then used a plumbers wrench around the stud but that broke off too. The plumbers wrench method worked on the other catalytic converter (V6 engine). Of course, I WD-40ed the hell out of it but it didn't help.

How can I remove these broken off rusted studs without going to a machinist to be charged an arm and a leg? I am trying to not have to buy a whole piece just because the broken studs ($240).

amphibient
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4 Answers4

7

Your best bet is to use heat.

Take a torch (propane will work just fine) and heat the stud portion until it is cherry red. Then douse it in PB Blaster or WD40 or just about any other lubricant. Then grab the stud with a pair of locking pliers. Even the short one should be long enough for you to do this. You should be able to walk it out, working it back and forth until it is removed. You want to unscrew it from the broken side, as if you try to screw it through to remove, you'll damage the threads in converter. To make the job a little easier, if you can cut the threads off flush with the back of the converter flange, it will mean less for you to remove and less rust to plow through during removal.

Once removed, you'll want to clean up the threads with a tap. Be careful, though ... you don't want to cut new threads, you just want to clean up the old ones. When putting new fasteners in, it is a good idea to hit them with some anti-seize. I use copper based anti-seize for exhaust parts as it stands up to the heat better.

Pᴀᴜʟsᴛᴇʀ2
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6

Not exactly what you're asking for, but maybe a different solution. I had similar problems with a couple of Chevys. More-or-less, I cut the studs flush, and used a pair of 'split flanges' to join the ends. (picture below.) It took a lot of effort (at least for me) to find ones with the right geometry, but there seem to be a lot of choices. Walker makes some. I got mine from Exhaust Direct Ltd in Canada, who had a large catalog of them.

My most recent are still holding after almost 5 years.

split-flange coupling

George
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5

These bolts can be very difficult to remove due to the rust and heat they are exposed to. The threads are rusted both externally and internally.

I've had some success with the following:

  1. Soak with a penetrating oil like PB Blaster for a day or two. Then try to remove. You have enough bolt extending that a pair of locking pliers should be able to grip. If not, get an EXTERNAL screw extractor.

  2. If that fails drilling out the majority of the bolt while being careful not to damage the flange threads is usually successful. A drill press is your friend here as doing this freehand with a portable drill is tricky.

Good luck but you might reconsider your stance on taking this to a machinist.

jwh20
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0

Yes - use bolt loosener, let it soak for an hour. Make flat spots on the sides of the bolt with a file or, prefereably, an angle grinder (because it will also get it hot - crack rust) and then... locking pliers really tight - bang on end of bolt with hammer while turning. If it turns a little bit and jams, add more loosener juice - go backwards - more loosener juice - then go for it.

BitHead
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