Slotted Nut? (1 Viewer)

[97 AZ LC]

I'm trying to separate the catalytic converter from the exhaust manifold on the driver side, or what's left of the cat after the main body was stolen. It's a triangular flange with 3 studs on the manifold side and 3 nuts underneath on the cat side. Two of the nuts came off easily but the third won't budge. The nuts have a slot on the top. What's the purpose of the slot? Do I need to do something to release it? The first two came off by hand but the third won't budge even with an impact wrench. I'm wondering if there's a secret here that I'm not in on.

 

[KLF]

Those are special nuts that Toyota uses on exhaust studs, as you found them. They are heat treated, and they "pinch" on to the stud so they don't come loose after many heat cycles. They are not intended to be re-used, you should get new ones when re-installing.

Sometimes you just gotta put the muscle to them to get them off, and occasionally they take the tip of the stud with them, which is a PITA to fix. Marinate in your favorite rust penetrant (Kroil, etc), then some heat and you might get it to come loose.

 

[97 AZ LC]

I've done several days of PB Blaster. The first two nuts came off without anything. I'd better clean the whole thing up with a wire brush / wire wheel. Some crud in those slots would be a problem. I'm wondering if I can pry open the slots a bit.

 

[FlammableFishie]

Have you tried heat?

 

[97 AZ LC]

Have you tried heat?

No, not yet. What's the least risky way to apply heat there? Does it have to be open flame torch?

 

[FlammableFishie]

Are there wires that you're worried about? I'd probably use a propane blow torch.

 

[97 AZ LC]

It's unfortunately sitting in a public parking garage with a sprinkler system, etc. I've got some other things to try before heat. I haven't had a good disaster in a while but I should probably tow it to a shop for an open flame - which would kill me because I haven't taken a car to a shop for at least 15 years.

 

[97 AZ LC]

It finally broke loose. A couple more days of PB Blaster plus I really cleaned up the slots and threads with a wire brush / wire wheel. A trip to the dealer confirmed that there is no secret method of releasing a slotted exhaust nut, which the parts guy called a "locking nut". It just takes brute force. I'll get some new nuts. Thanks for the help.