Was driving my 87 4runner today, when all of the sudden it sounded louder, and not in a good way. It sounded like a playing card in a bicycle spoke. I limped it home and took a quick look. I removed the heat shield from the manifold and took a look. The exhaust manifold was rusty, but I diddnt see any visible cracks, however it was rusty and flakey looking. When running, I felt hot air coming out oc the side of the manifold. I assume the problem is the exhaust manifold, however I am not sure. Is there anything else this might be? Can they crack all at once like that? I had no previous signs. Is it safe on the car to drive like this?
Thanks

 

Did the hardware come loose ?

Causing the gasket to fail ?

If the exhaust system is supported correct the Manifold should almost never crack .

The exhaust fumes leaking in the engine Compartment can easily be drawn into the cab

 

By any chance are you missing the bellhousing bracket and clamp for the downpipe? If so, that can cause a sudden manifold gasket leak, happened to me. Especially if you are using one of Fel-Pros old-style gaskets that appear to be made of cardboard, as I was at the time.

I second testing all the manifold nuts, they shouldn't budge if you try to snug them up a bit (use a torque wrench so you don't over-do it and strip out a stud).

It's probably safe to drive a short distance if you have to, but fix it up asap.