My '94 GSR was making a buzzing sound around 3k RPMs so I figured it was the common manifold crack problem. I removed mine and I have heard that the cracks can be small but I can't see any evidence of cracks anywhere. I am removing all of the heatshields. I want to know if there are any ways to check the manifold visually.

Thanks.

 

well, when i check for exhaust leaks i lift the car and go through my rpm range while someone feels for air coming out of places it shouldn't be coming out of. but since it's off? water is not a good thing, but if you're careful and dry everything out well you can seal off the ends and put some water through it and see if any leaks out, but you have to have it preasurized. same thing works with blowing air into it while the whole manifold is submerged.........

have you checked all your bolt up connections and gaskets?

 

I don't know if that will work, I ahve read that the cracks can be very, very, very small. I think I just might put mine back on and see how it goes with the heatshields.

 

i have the exact problem on mine
a buzzing at 3k
I THINK that the inner core of the mani has seperated from the outer, and that is what it is. You can have them rewelded together, or can just use it as an excuse to fork over the cash and buy a new header (thats what im doing)
It gets worse, mine is really loud now

 

You could also look for light carbon buildup.
I had a small crack on the weld of my DC headers, and I saw it because there is carbon buildup around it.