What to fix exhaust pipe at manifold car bottomed out and the came off bolts still looks like there is a rusted nut on end of but flange goes past nuts?

This sounds like a frustrating situation! Because the exhaust flange extends past the rusted nuts, simply replacing the bolts won't solve the problem. The nuts are likely seized onto the studs (the threaded parts sticking out of the manifold). Here's a breakdown of how to fix it:

1. Assessment:

* Rust Severity: How badly rusted are the nuts? Are they completely fused to the studs? Can you see any of the stud threads?

* Flange Condition: Is the exhaust flange itself damaged? Bent? Cracked?

* Stud Condition: Are the studs themselves broken or stripped? This is crucial.

2. Options, depending on assessment:

* Option A: If nuts are somewhat accessible and not completely fused:

* Penetrating Oil: Liberally apply a penetrating oil (like PB Blaster, Liquid Wrench, or Kroil) to the nuts. Let it soak for several hours, or even overnight. Reapply multiple times. Heat can also help the penetrating oil work, but be *extremely* cautious near the manifold and fuel lines.

* Wrenching: Use the correct size wrench (open-ended or combination are best for this situation) and try to carefully loosen the nuts. Use a breaker bar for extra leverage if needed. Go slow and steady to avoid stripping the nuts or breaking the studs. If it's really stuck, consider using an impact wrench, but *be gentle* and monitor for stud damage.

* Bolt Replacement: Once the nuts are removed, inspect the studs carefully. If they're good, replace the bolts. If you're not sure about the studs, it might be better to go with option B or C.

* Option B: If nuts are severely rusted and/or studs are questionable:

* Nut Removal Tools: Consider using specialized tools like a nut splitter, a Dremel tool with a cutoff wheel (extremely carefully!), or even an easy-out (as a last resort). These methods require skill and caution to avoid damaging the studs or manifold. Watch several YouTube videos on these techniques before attempting.

* Stud Removal and Replacement (Likely Necessary): The best option might be to remove the broken studs and replace them with new ones. This requires precision drilling and an easy-out (or similar tool) to remove the broken pieces of the old studs. Then, you'll need to install new studs (thread appropriately sized ones into the manifold holes). This is more advanced and might require specialized tools.

* Option C: If the flange is severely damaged or studs are broken and/or inaccessible:

* Exhaust Replacement (Most Likely): This is the most costly but sometimes the only practical option. It might be more efficient to replace the entire exhaust section from the manifold back, especially if the damage is extensive.

Important Considerations:

* Safety First: Wear safety glasses and gloves. Exhaust systems get very hot, and penetrating oil can be flammable.

* Patience is Key: This is likely a time-consuming repair. Don't rush it.

* Professional Help: If you're not comfortable working on your vehicle, take it to a qualified mechanic. They have the tools and expertise to handle this repair safely and efficiently.

Remember to torque the new bolts to the manufacturer's specifications once everything is back together. This information should be available in your vehicle's repair manual. Improper torque can lead to leaks and damage.