I have a short bed 4-speed that I purchased new in 1980. The truck is all stock, does not get much use and the engine was rebuilt a few years ago. Recently, it seems to have developed an exhaust leak somewhere under the hood. It?s sort of louder when cold and gets a bit quieter as the truck warms up. The exhaust manifold was welded and re-machined when the rebuild happened, the muffler was replaced but the truck still has the original catalytic converter. The sound is almost like an engine knock, noticeable when the engine revs? Could the exhaust manifold be loose? Thanks for any feedback.

Gus

 

could have a crack in the manifold...i doubt its loose, mani could have rusted thru

 

I'll be willing to bet that either your manifold bolts are loose or else one or more of them have pulled out. I have fought with this on my 82 for 2 years and just recently got it quieted up and my dad fought with it on his 80 for a while as well. Its a common problem on these older trucks. I tapped mine out to 7/16'' and it worked for some of them. I only have one original stud. All the rest have pulled out.

 

82yota is right , I drill mine out and Heli-coil them seems to fix them .

 

Thanks for all the replies. It was a stud problem. Plus the gasket/heat shield (20R) was shot. The gasket/heat shield cost over $100 at Toyota. I replace it, other gaskets and all studs and nuts and it all went back together well. The new studs are longer and have a nice torque-nut on the end for installing with sealant on the head-side threads.