Hewitt Bypass system and an exhaust manifold leak.

[CapnSpaulding]

My 09 came with this bypass system installed from the previous owner. It also came with an exhaust leak coming from what sounds like the middle of the exhaust manifold on the driver side.

Thinking at first it may have been a misaligned blocking plate, I physically removed the bypass plate at the back of the manifold and then reinstalled it today myself and found no issues, nor do I think it’s leaking right there after all.

I’d normally chalk up having a bypass system as a coincidence given it could just as easily be a cracked manifold or a bad gasket, however, when looking at Hewitt’s own installation YouTube video, about 40% of the comments all state the same sorta thing - installed these plates and now I have an exhaust leak, please advise. Hewitt never replied to any of those requests however.

Do we have any theories as to what may be causing this, before I tear into an exhaust manifold that may not need to come out? Maybe additional pressure with that port blocked off causing a weak gasket to fail? Also, any DIY ways to test the exhaust manifold for a leak to confirm the location?

My leak isn’t terrible, but the ticking is driving me crazy and the exhaust smell that occasionally enters through the vents is not safe.

 

[08URJ200]

Main reason my Hewitt kit is still on the shelf. Doesn't mean it caused your problem initially but I also don't trust the add-a-plate solution to a sealed exhaust manifold. To test for exhaust leak on my 258 4.2L, we would add a small amount of ATF to the intake by inserting the tip of a carb vacuum hose into a small cup of ATF. Moments later thick white smoke will pour out of any leak you have. If no leak, all out of the tail pipe in a few minutes. Easier to do on a way simpler engine of course. You can likely do the same on the 5.7. A 30 yr technician showed me the trick and said it causes no harm rather it can clean up some of the insides. google research it

 

[OregonLC]

Have you smoke tested to make sure you actually have a leak? I ask because at about 120k I proactively replaced my starter. To do so I also removed and re-gasketed the passenger side, both at the head and the down pipe. The driver's side also had a 'put-put' sound (not a bright tick like would come from a crack) so I R&R'd that side and replaced gaskets along with inspecting it for cracks. Zero change. No soot witness stains either. So I'm inclined to believe that the 3UR in the 200 just has a muddy note to it under mid-throttle. Ironically, the 100 with it's stone-age single collector exhaust sounds fantastic in comparison.

The CAI system only injects fresh air, it doesn't provide an additional exhaust path. So there should be no back pressure change. Perhaps there could be a tone change if the tubing adds a resonance character to the note.