M54 Ticking Noise - Catalytic Converters?

[Canadian_E53]

Hey everyone,


I just recently finished replacing the head gasket and time serting the M54 in my wifes E53. During the job I replaced the lifters as well. Everything back together and car runs great. I can't for life of me get rid of what I think is a ticking lifter noise.


I'm assuming it's the lifters because there was no ticking noise before the head gasket replacement. I've tried literally everything to quiet them down (lifter additive, oil replacement, lifter bleeding procedure (holding high rpms for several minutes), timing chain tensioner.


I'm now leaning towards it being the catalytic converters. I was poking around again with my stethoscope and it sounded like the ticking was loudest when I touched the tops of the exhaust manifolds and on the catalytic converters as well. When I was doing this job I had to bang off the studs of the catalytic converters. I believe I may have damaged them and now this is the source of my ticking. It would be very strange to me if this was the case as it really does sound like a lifter tick or rod knock...but hey who knows.


I'm going to decat the car and put some headers on it next in an attempt to resolve this ticking as i'm leaning towards it being bad cats.


Here is a video clip of the ticking noise:
https://www.youtube.com/shorts/Ja395cOJRfE



Thanks
Tyler

[80stech]

You should be able to easily isolate a lifter sound with a stethoscope or piece of hose.

[Factory6speed]

It's very loud down in the wheel well so I think you're right about exhaust manifold / cats, especially if you just worked on them.

When I had the transmission off I had the rear O2 sensor wiring all down and out of the way. When I put everything back together, there was a horrible tapping noise, not unlike what you have, though I don't really remember. It was absurdly loud though. I was panicking but then I noticed it changed if I slapped the valve cover on top of cylinder 6. I kept looking around and eventually found the wire harness bracket back there was about the source of the noise. A couple minutes to get everything repositioned right so it stopped and all was well. So I would suggest checking all those brackets, the rear O2 wire sensor brackets, which you had off with the head right, the exhaust brackets etc. If you leave it running before it gets hot and just start hitting everything you might be able to find what it is.

Good luck. I have the head off of the m52 on my E36 now and it is just a monumental amount of work. Respect. It is taking me months to clean things. Tonight I was supposed to remove the exhaust manifold from the lower end and get them out and pressure wash the cats out but that didn't happen.. maybe tomorrow

[X5chemist]

I've had failed cats. Bad cats rattle. A tapping sound is something else. I suspect something is loose too.

Mine had lifter noise, so did my '21 HEMI at start up. LiquiMoly Ceratec additive stopped the ticking in both. One can will last 30k miles. Both vehicles are close to their next oil change. I'll see if the ticking stays away. So far, I'm happy with results.