The exhaust manifold on the 3.0 liter engine often warps and cracks, breaking off the studs between the cylinder head and the exhaust manifold. The noise may be most noticeable when the engine is cold.Google+
Car Problem Reports
Nissan Pickup (D21) Exhaust Manifold Can Warp and Cause the Studs to Break Off
Nissan Pickup (D21) Problem
Average Mileage: 148,840 mi (90,000 mi - 232,500 mi)
Visitor, 1995 Nissan Pickup (D21), 143,000 mi
Exhaust manifold cracked along with the ex. man. studs breaking. Head seems to have been machined unevenly.
Visitor, 1990 Nissan Pickup (D21), 232,500 mi
exhust manifold cracked broken studs
Visitor, 1995 Nissan Pickup (D21), 90,000 mi
I've wondered where the ticking sound came from. I only hear it when the engine is cold.
Visitor, 1993 Nissan Pickup (D21), 125,000 mi
a ticking noise at engine mostly on passenger side
Visitor, 1991 Nissan Pickup (D21), 153,700 mi
loud ticking from the engine... most likely a hole in the manifold. only at idol is when you hear the loud "clapping"