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There are a few things it could be. Valve stem seals, piston rings, to name two. The first thing I would suggest is that you run a compression test, write down the readings for each cylinder, dry, then wet. Follow this with a cylinder leakdown test. These tests will give us clues as to how the oil is getting to the fire.
Valve adjustments are neither complicated nor terribly expensive, couple hundred dollars, but if you decide to have it done, do not be surprised if the noise persists. What I heard in the video you posted sounds like a “normal 3.7” to me, and just isn’t fixable. They are noisy.
Take the drive belt off and start the engine and see if the noise goes away. If you have more than one belt (my Hyundai has more than one), do them one at a time. If all the belts are off and the noise is still there, it isn’t a belt-driven accessory noise. If the noise does go away, test the pulleys on everything that the removed belt drives. Yes, it is okay to run your engine briefly without the belts. This test is important to conclude whether it is or isn’t a belt-driven noise, and will point out which accessories may be to blame if it is.
If you have the distributorless ignition, it should manage the ignition timing on its own, so you are correct that it cannot be manually adjusted. In that case, it sounds like your cam is not on the right tooth. Can you describe the procedure you did, and the marks you used, when installing the new belt? Do you have a service manual for this car, and did you reference it during these two jobs?
If one side’s brake is working properly, and the other side is not, there is either something wrong with the fluid line (blockage or restriction, or air in the line), or the caliper is not working correctly.
I’m not talking about the timing belt. I’m talking about setting the ignition timing (with a timing light, setting the correct number of degrees). The specification for timing degrees and idle are found on the underhood sticker, or in your vehicle’s service manual.
1) make sure your timing is set to spec at the correct RPM.
2) make sure there is no air in the system. Did you bench bleed the master cylinder? Did you bleed the calipers and make sure no air bubbles were in the new lines?
It’s usually a small flat rectangular box with a few (4 maybe?) wires connecting to it. It is not inside the cap, probably mounted on or near the coil. It is mounted on top of the coil on my Toyota. If your coil is inside your distributor cap, as it is in some Honda’s, then the igniter should be also.
There are probably several other things, but it looks like you found the source. Take care of that first before looking for other things.
The 3.7s and 4.7s are notorious for having loud valvetrains. There really isn’t anything that will fix it, it’s the way they were made, just make sure the oil maintenance is kept up properly.
Usually this behavior is caused by a contaminated crank angle (TDC) sensor. Since it was replaced and didn’t solve the problem, it makes me wonder if the original was actually bad. I find more and more often mechanics just swap things like this without actually testing them. I guess there is no money in 2 minutes with a volt-ohm-meter. Anyhow, this is a perplexing problem since it only happens when warm and the usual fix (to clean and test/replace if needed the TDC sensor) didn’t work. When I read your headline, my first thought was “crank angle sensor” only to find in your comment that it has already been replaced. I have extremely limited knowledge of Peugeot, having only worked on one in my lifetime, 20 years ago. Hopefully someone with more knowledge of these cars will be able to help. In the meantime, check all of the electrical grounds to make sure they are clean, intact, and secure. Also make sure the battery is in good condition. How old is the battery? I’ve seen cases on other cars where a battery that seems fine actually isn’t and plays havoc with the engine computer.
Speaking only for myself, I wouldn’t do it to any of my vehicles. I only use auto trans fluid (ATF) or purposely-made motor flush for this, and in extreme cases, Berryman B-12.
ATF might work, although I would be tempted to use a stronger solvent such as Berryman B-12 or a quart of motor flush. Oil starvation is a big problem. If it can’t be cleared using solvent and oil changes, a rebuild may be the only way to fix it. You may want to pull the valve cover on the other bank to see if they are dry too.
In your engine, rockers are oiled through the shaft. It is possible that a blockage or RTV booger could be blocking the oil from reaching the rockers. If you remove the shaft assembly, you will see an oil hole from the head to the shaft. I’d start looking for a problem in that area. This passage from the head, or the shaft itself, could be plugged up.