Exhaust Manifold Leak (Suspected): Tips, Suggestions, Experience?

[CruelJung]

I have been driving my '08 Yukon XL for nearly four years now, and it has always made a 'ticking' noise on cold startup. This noise subsides within a minute or so, as the engine temperature rises. No CEL or codes. Over the past four years I have been gaining more automotive knowledge and competency, as well as developing a general obsession with this vehicle--how it runs, how it sounds, how my maintenance/repair choices will affect a trajectory towards supercharging one day...

So, I started chasing this 'ticking' noise a few months ago because I noticed an exaggerated form of it under load while driving with the window down. When looking for a busted exhaust manifold bolt, I found that the second-to-rearmost manifold bolt on the passenger side was loose enough to turn with my fingers. There was also soot visible in a few areas above and below the manifold flange. I torqued all 12 bolts to 18 ft. lbs.--noting that all but one bolt were under 11 ft. lbs.--and the result was less noise for less time when cold starting and still noise under load.

Having some free time, last week, I decided to revisit the manifold bolts again because the cold start 'tick' duration seemed to be increasing. Sure enough, the bolts were under the 18 ft. lb. torque spec again and--once re-torqued--the cold start noise level and duration were reduced.

Presuming that the sound (when cold and under load, but dissipating in idle from cold to operating temperature), visible soot, loose bolts (potentially walked out and damaged gasket seal?) point towards an exhaust leak, I am planning to do the following:


1. Replace the current, rusty hardware with ARP header bolts
a. Leaning towards ARP 434-1102 (SS, hex)
b. Considering ARP 434-1301 (SS, stud/nut)

2. In conjunction, replace the exhaust manifold gasket (without removing manifold entirely--i.e., not disconnecting from Y-pipe)
a. Leaning towards OEM (Genuine GM), AC Delco, or Mahle
b. Considering a Remflex gasket or double Remflex gasket to compensate for any warping of the manifold

3. See what happens
a. If the sound persists, I will try to tighten the studs (manifold to Y-pipe).
b. If sound STILL persists after "a.", then I will remove manifold entirely to inspect, replace manifold-to-Y-pipe gaskets, and potentially replace the manifold.


With all of that said, do any of you with experience have some advice for the materials, process, or--for that matter--diagnosis?

 

[j91z28d1]

just my opinion and others do completely different and it works well for them too. but I like exhaust manifold studs. I feel like stainless steel is to soft for small m8 these engines use. I like the Dorman ones of all things, originally found them listed for a mustang, since they use the same size. but different amount M8x1.25 is the size.) don't rust are 10.8 grade and the nuts are flanged crimp locking nuts, so I've never had one come loose.

to me the oem gaskets have been good, but I have no experience with the others, they might be good too.

for exhaust leaks, the best way I've found to find then is the mechanic stethoscope but remove the metal tip so you have a open hose, run that hose along anywhere you might have a leak and you'll hear a puff puff puff clear as day.

 

[j91z28d1]

these were on the car about 5 years..

I only recently removed them because the headers I bought came with titanium Hardware, which I'm scared is to soft was well, but I gotta admit it's kinda special looking and when you put 2500$ headers on your car, you do dumb things for looks sometimes haha.

the arp bolts are strong, but without a locking thing, I'm not sure they are really much better for you. someone found a set of bolts that are split with a set screw in the middle. once you tq the bolt you tighten the set screw to lock the bolt. I've used them on old school 3/8 sbc stuff because you need all the room you can get and studs don't work. had good results with them in that size.