When I start the truck I hear a 'tsst tsst tsst tsst' sound at idle when standing next to the doors/bed. I crawled under with the truck running to try and find the hole, but once I got down there I follwed the sound up towards the engine and lost it.
Is my head playing tricks, is this a normal noise? It sounds alot like an exhaust leak to me...

 

i say rip it all out and put new a 4-5 inch straight exhaust throught it. fixes ur prob but does cost money which i dont have. u could try to weld it if u find ur leak.

 

I hear this on mine if I stand outside while it's running. I think it is probably the lift pump pulsing. I don't know if a new overflow valve would quieten it down or not but that is what is often suggested. Check if you can hear it on the drivers side with the hood open. Hope this helps.

 

I've already got the 5" exhuast all the way back, no cats.

 

I would replace your overflow valve. A friend has the same ticking noise before he installed it. It completely went away after the new one was installed and it is cheap and easy to do.

Jim

 

Just curious, did you ever discover what was making the 'tsst tsst tsst tsst' sound? My '96 makes the exact same noise, I also loose it when I get near the engine, it seems more clear around the doors and under the truck. Was it an exhaust leak, or the overflow valve/lift pump? I turned my idle up, and the sound softened up, but its still there. Is it normal for these trucks, this is my first 12-valve.

 

The exhaust manifolds on these engines have a tendency to shrink and crack or not seal to the head well. Makes a ticking noise especially at idle.
Inspect well even underneath with a mirror. First indication that this might be your problem is that the #1 and 6 cylinder manifold bolts are visibly bent.

 

I have not narrowed down my tsst noise yet, I was more concerned with my squealing problem that turned out to be a worn belt.

I'll get after the noise now...should be fun in this heat!

I really want to check my fuel pressure, I'm just nervous drilling/tapping on my block...

 

If your hearing that noise standing beside the drivers side its probably the fuel tank vent, mine had a noise like that and after doing alittle searching here I found that some fuel tanks have a red or black dust cap left on them from the factory. I removed mine and the tick went away I guess it was building to much vaccum your tank should build alittle but mine was to much it was making the fuel cap hard to get off and would let off a tremendous amount of pressure I think infidel has seen fuel tanks with the sides sucked in because of the vaccum.

 

I hear it on every 12 valve I see... its the lift pump and you should not worry.