Quick Links: "Case Study"
The way the S54 is laid out there is rather thin walls (app. 4 mm) between the cylinder bores. This means that there is a relative higher risk that the cylinder head gasket may break at these thin points.
When this happens highly compressed gas (both before and after combustion) will flow into the neighboring cylinder.
One would expect that this would cause major problems - and it may if the blown away section is “big” or if the car is driven long time with the problem unattended. However, it may cause surprising little malfunction – at least in the beginning. Some drivers may not even notice the problem in the earlier stages – and a computer diagnose may not either detect the problem. See below my personal "case study".
By the way the head gasket may “blow” between two cylinders in different ways: The head gasket is made of 3 layers where the middle layer may be “blown out”, or 2 or 3 layers may be “blown out”.
Blown head gaskets are probably caused by the head bolts loose some tension over time. The problem occurs, but it’s not my impression, that it is very frequent – and the phenomenon is not mentioned as “An Issue” on line with rod bearings, Vanos and RACP. However, if you are about to buy an E46 M3, it’s advisable to be extra observant on pinking noise. As described in the “case story” an electronical diagnosis may not detect a blown head gasket. If you want to be sure that the car in question doesn’t have the problem a compression/leak test is the way forward.
Video: S54 Head Gasket Failure Tech (E46 M3, Z3 M, Z4 M).
For more information on engine rebuild etc. see 01 ENGINE.
My own “case study” on blown head gasket:
My M3, which I bought in Belgium, had some faults. Some of these flaws I knew when I bought it, but others I only discovered later. That's the way it is - and if you cannot live with it, then you should not buy a 16-year-old BMW M3.
One of the problems I discovered later was a suspicious sound (“The Noise”) from the engine (or engine compartment), which sounded like ignition knocking/pinking. In the cabin, the sound could primarily be heard at 3,000 rpm plus / minus and light throttling. At cruise at this speed I couldn’t hear the sound and neither at full throttle.
It could be something completely different - for example a component, heat shield or the like, which vibrated and then it was a trifle. But if it was the ignition pinging, then it was serious and HAD TO be corrected.
I guess the reason I did not discover this sound in Belgium was that it was raining the day I test drove and bought the car. The rain against the body must have drowned out the crisp sound.
In June (2020) I got me an appointment at Bayern Auto Group in Aarhus. It's a long way to drive, but from the past I knew André, who works here - and he knows what he's talking about in terms of M3 - not many people do that, even though they claim that "they know it all". André test drove the car and tested it through from A to Z. No faults at all on the engine, sensors, Vanos, etc. André pointed out the bearing play that it had in the differential's right output shaft and that the front rubber bushings for the triangles were probably a bit old and soft - but otherwise nothing else on the car. He could not find the cause of the "ignition knocking/pinging sound", as it also did not come from the plastic cover at the top of the engine (he found a BMW note that it can rattle as knocking if the distance to the cylinder head is not min. 2 mm).
Of course, I was sorry to have taken the whole trip from Rønnede to Aarhus with accommodation without solving the problem - but I cannot blame André or BAG because the phenomenon is obviously quite rare - and chasing sounds/noises is not easy.
Subsequently, I trawled the internet and found a BMW Service Bulletin (SI B13 01 07), which mentions something that might look like the problem. However, it turned out that this Service Bulletin is not known in Denmark (Europe), but only the USA and Australia - and that the treatment it prescribes requires the use of a special agent (Fuel Injector and Induction Cleaner Concentrate), which I acquired, but also an application device, which apparently only BAG has here in Denmark (which I found out later). A source stated that Chevron's Techron was similar to BMW's special concentrate and that it could be poured into the tank. Long story in short: I bought some Techron and ran two full tanks with it. It did not help.
After a few attempts with my action camera in the engine compartment while driving (could only record sound due to lack of light) I came to doubt whether it was the ignition knocking/pinging at all.
The next step was to get a small microphone (connected to the mobile) and records the sound in different places in the engine compartment - in the hope that I could identify where the sound comes from.
I made 4 recordings, each with a different microphone location. No audible variations were found.
A friend helped me getting and using some sound processing software (Audials), which in combination with a dash cam, a small microphone and not to forget Open Shot Video Editor enabled me to make the below video.
The video has explaining text and should be encapsulating the problem.
Video has some recordings without "The Noise". This is to give a reference and an idea of, how specific the conditions for "The Noise" are. In the video RTS stands for Real Time Speed (of sound replay).
As stated in the video I ended up with a complete engine rebuild. Perhaps it was an overkill, however since I needed (wanted, really) new rod bearings, a couple of the cylinders were not quite up to best compression (130-140 psi) and the head gasket had to be replaced anyway, I decided to go all the way – including all new bearings, new pistons, chains, water pump - and clutch.
