Hey guys, I have been battling an exhaust leak problem since shortly after i purchased my truck over a year ago. I have a 94 f-150 with the 5.8L. The exhaust ticks under load and during acceleration from what seems like the passenger floor or firewall area. I have a y-pipe dual exhaust with no rear cat and a gutted front cat. I thought my passenger exhaust manifold was leaking, so i replaced it since it was warped, and put a gasket in there, and it quieted down a little, but i still get the ticking under load. Could the leak be coming from the thermactor tube that runs behind the motor from head to head? What would be a good way to narrow down where the leak is coming from. I want it fixed soon, it is driving me nuts!

 

Welcome to the forums.

Ya, could be the cross over tube behind the heads, or the tube going down to the cat.

If you can't get it on a lift, wait for everything to cool down, start it and get under there quickly(after blocking wheels) and feel around before it gets hot. Should be easy enough to notice if you can get your hands around the general area.

 

Its really hard to hear it at idle though, the only time you can hear it is when it is in gear. Also, i have access to a lift

 

Get it up, have someone start it and you feel around(maybe have it cooled down some). You should feel air blowing around if it is leaking bad enough.

Maybe have said person "powerbrake" it lightly to put a load on it. Try not to kill yourself or anyone around it.

 

There's a few areas this could be coming from:

The AIR injection pipes, as you mentioned, are known to fail. I removed my smog pump and all piping a couple of months ago, because everything was leaking.

There's a small pipe welded between the two pipes on the Y, where the O2 sensor screws in. I've seen a couple that have leaked there.

The EGR tube.

The flanges from the y pipe to exhaust manifolds.