[fdolcater]

I've got an 06 2wd access cab. I'm getting an intermittment clank sound - almost sounds like metal on metal - when I let off the gas after accelerating (never from a constant speed). It appears to happen most when the engine is cold but I have gotten it a couple of times when it was warmed up. I looked at the TSB for the exhaust ticking sound but that doesn't appear to be it because it only happens once as opposed to a tick-tick-tick sound. I did have the exhaust manifolds replaced for the sulfur smell. Could that sound occur if the didn't get the torque right and the manifolds are slightly loose?

The sound appears to be coming from the rear of the engine compartment but it is not always from the same place. I haven't approached a the dealer yet. It's so intermittent it may not happen for a month and then it will happen several time and the stop again. Any advice on what to look for would be appreciated. I'm stumped

 

[flyman767]

My first indication was the exhaust manifold cover. I know on some Toyota engines in the past the metal to metal sound was the metal itself expanding and contracting as the engine warmed up and cold down. Since you said you just had work done, I would suspect that maybe the cover or exhaust system is loose. You mentioned the noise coming from the rear, maybe when they were working on the exaust manifold they knocked loose or broke a bracket off the exhaust system where it mounts to the frame causing the metal to metal sound your hear when letting of the gas. Also, possible the tech forgot to install a bolt or two in the brackets themself. I would have the dealer who did the work check it out.