It is not uncommon one or both of the exhaust manifolds to crack resulting in an exhaust leak. Symptoms will begin as a ticking type noise noted on acceleration when the engine is cold.Google+
Car Problem Reports
Infiniti QX56 Exhaust manifolds crack and make loud noise on acceleration
Infiniti QX56 Problem
Average Mileage: 94,143 mi (64,000 mi - 135,000 mi)
alomst exact same problem; took in to replace a "sensor" and EGR valve and was told BOTH manifolds were cracked and cost to repair was going to be $2,800!!!! i was also told that this was VERY common in the QX line of vehicles becuase they are made from stainless steel and not cast iron and the SS does not hold up to the constant heating and cooling they experience. sure seems like INFINITI would do the right thing and own up to a manufacturing defect and fix this problem out of THIER pocket
The exhaust manifolds have built-in catalytic converters. Excess heat causes early ones to crack. Loud popping noises are heard on hard accerlation, like merging onto a busy freeway. Your test drive should include merging onto a freeway. Both of mine were replaced under warranty. I recently (Jan. 2011) received a letter from Infiniti that the warranty on these had been extended to 8 years/80,000 miles because they are an "emissions" component.
Visitor, 2005 Infiniti QX56, 90,000 mi
Exhaust manifolds were severly cracked and popped when accelerting. Nissan wanted to charge $4k plus. Midas sent them to a machine shop, complete fix at $400 (sigh of relief).
Visitor, 2005 Infiniti QX56, 119,000 mi
Same issue as everyone else who posted here. We were out of warranty when it was discovered and the dealer wanted over $2800 to repair.
Visitor, 2006 Infiniti QX56, 120,000 mi
Cracked manifold. I removed and welded the crack. Hope it holds up cause its a bitch to get off and on.
Visitor, 2006 Infiniti QX56, 70,000 mi
Heard ticking sound on acceleration. Mentioned it to the dealership but they did not say anything to us about the manifold being cracked until 90,000 miles and an expiration of the warranty. Whatever!
Visitor, 2006 Infiniti QX56, 90,363 mi
Ther is a ticking sound in my dasboard and I went back to Cerritos infinity and they will not even check it out for me they will not look at it. They said I am out of warrant.
Visitor, 2004 Infiniti QX56, 82,000 mi
not yet fixed, was informed by dealership about both exhaust manifolds cracked 8 months ago (4/13)
Visitor, 2006 Infiniti QX56, 72,000 mi
manifold cracks and engine starts making noise like its a diesel engine upon acceleration and startup
Visitor, 2006 Infiniti QX56, 125,000 mi
Passenger side at 125000. Took off, welded crack, reinstalled. Works great
NOW, driver side cracked. Grrrr.... Tear down tomorrow. Oh, when removing pass side you must jack up engine and remove motor mount bracket from block.