4-part interview with Bernd Ramler, the man behind the M156 engine (German)
4-part interview with Bernd Ramler, the man behind the M156 engine (German)
Super Member
Joined: May 2014
Posts: 533
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From: England - UK
C63 AMG Saloon
Just watching the third video, are they really saying when doing an oil change don’t drain the oil coolers?
Why would you not do that and leave old oil in mixing with new oil. If that is what they are saying that doesn’t make sense to me.
Why would you not do that and leave old oil in mixing with new oil. If that is what they are saying that doesn’t make sense to me.
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2017 GLE350 4MATIC
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From: NJ
2009 SL63 AMG
The M156 has been out for a long time, with many enthusiasts and professionals draining from the oil cooler.
Anyone here ever hear of an issue with air pockets being created from this? Because it's a first for me.
That said, the R230 has a top mount bolt and I drain the oil cooler by disconnecting one of the lines...so technically I could pre-fill it.
Anyone here ever hear of an issue with air pockets being created from this? Because it's a first for me.
That said, the R230 has a top mount bolt and I drain the oil cooler by disconnecting one of the lines...so technically I could pre-fill it.
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~ 2011 E63 AMG
Jean-Pierre brings up the dreaded head bolts issue, and mentions a previous engine that he's worked on. He's referring to an ML63 with over 450.000km (279k miles). All mostly Autobahn kilometers, regularly maintained, never cracked open. When he opened it up, he found it in really good condition, and what's best - the head bolts were fine.
Turn on subs/dubs, it's also very interesting to see, since I've never seen an M156 engine with such high mileage before, and the condition it's in.
Turn on subs/dubs, it's also very interesting to see, since I've never seen an M156 engine with such high mileage before, and the condition it's in.
Last edited by WeisseTiger; Jan 20, 2026 at 02:48 PM.
Super Member
Joined: May 2014
Posts: 533
Likes: 146
From: England - UK
C63 AMG Saloon
The M156 has been out for a long time, with many enthusiasts and professionals draining from the oil cooler.
Anyone here ever hear of an issue with air pockets being created from this? Because it's a first for me.
That said, the R230 has a top mount bolt and I drain the oil cooler by disconnecting one of the lines...so technically I could pre-fill it.
Anyone here ever hear of an issue with air pockets being created from this? Because it's a first for me.
That said, the R230 has a top mount bolt and I drain the oil cooler by disconnecting one of the lines...so technically I could pre-fill it.
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12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG + Ultima Can-Am sold)
An excellent and very interesting insight to the M156 engine. Impressed by the condition after 450'000 kms
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Joined: Jan 2018
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From: Whitehouse Station, NJ
2012 C63 P31 Sedan
Not sure about the whole air pocket thing, but it could make sense that you may get a temporary loss of flow/pressure as the oil pump would need to fill the now empty cooler before oil would start flowing out.
I guess the effect of this would be based on where the cooled oil is supposed to travel next. Personally, I never bother draining the cooler because mine is driven so infrequently that I replace the rest of the oil in 3k miles or less.
I guess the effect of this would be based on where the cooled oil is supposed to travel next. Personally, I never bother draining the cooler because mine is driven so infrequently that I replace the rest of the oil in 3k miles or less.
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~ 2011 E63 AMG
This segment of the video features a technical discussion between mechanic Jean-Pierre and engine builder Bernd Ramler. Jean-Pierre explains the mechanics of hydraulic tappet failure, emphasizing how air entry into the oil system leads to severe engine damage.
The Mechanism of Hydraulic Tappet Damage
Jean-Pierre describes hydraulic tappets as components designed to automatically compensate for valve clearance. He explains that they must remain filled with oil to function correctly. Because oil is incompressible, the tappet remains rigid under load. However, if air enters the tappet, it can be compressed.
When air is present, the thin metal surface of the tappet bends slightly under the pressure of the camshaft. This deformation changes the contact between the cam lobe and the tappet from a broad, flat surface load to a concentrated "point load" on the edges. This leads to accelerated wear known as "pitting," which can eventually be felt as rough spots on the camshaft lobes.
The first symptom of this issue is a persistent "ticking" noise from the valves. Jean-Pierre warns that while temporary ticking during a cold start is normal, it becomes critical if the noise persists as oil pressure and temperature rise. Pushing an engine to high RPMs while the tappets are still "ticking" causes the tappets to bend permanently, eventually leading to the catastrophic failure of the camshaft and the tappet's internal components.
The Danger of Draining the Oil Cooler
Jean-Pierre highlights a specific maintenance mistake that frequently introduces air into the system: draining oil from the oil cooler during an oil change.
While some owners or mechanics believe they are being thorough by draining every last drop of old oil, Jean-Pierre explains that this is actually detrimental for several reasons:
The Mechanism of Hydraulic Tappet Damage
Jean-Pierre describes hydraulic tappets as components designed to automatically compensate for valve clearance. He explains that they must remain filled with oil to function correctly. Because oil is incompressible, the tappet remains rigid under load. However, if air enters the tappet, it can be compressed.
When air is present, the thin metal surface of the tappet bends slightly under the pressure of the camshaft. This deformation changes the contact between the cam lobe and the tappet from a broad, flat surface load to a concentrated "point load" on the edges. This leads to accelerated wear known as "pitting," which can eventually be felt as rough spots on the camshaft lobes.
The first symptom of this issue is a persistent "ticking" noise from the valves. Jean-Pierre warns that while temporary ticking during a cold start is normal, it becomes critical if the noise persists as oil pressure and temperature rise. Pushing an engine to high RPMs while the tappets are still "ticking" causes the tappets to bend permanently, eventually leading to the catastrophic failure of the camshaft and the tappet's internal components.
The Danger of Draining the Oil Cooler
Jean-Pierre highlights a specific maintenance mistake that frequently introduces air into the system: draining oil from the oil cooler during an oil change.
While some owners or mechanics believe they are being thorough by draining every last drop of old oil, Jean-Pierre explains that this is actually detrimental for several reasons:
- Design Flaw: In several AMG models, the oil cooler lines enter from the bottom. If the cooler is drained, an air pocket is trapped at the top of the cooler.
- Venting Issues: Because of this bottom-entry design, the air pocket cannot easily be vented through the normal circulation of oil.
- Delayed Air Entry: When the engine reaches operating temperature (around 80°C), the oil thermostat opens, allowing oil to flow through the cooler. The trapped air is then pushed directly into the engine's oil galleries and into the hydraulic tappets.
- High RPM Risk: If the air is introduced while the engine is under load or high RPMs, the tappets will compress and bend, initiating the damage cycle described above.
Last edited by WeisseTiger; Jan 21, 2026 at 02:44 PM.
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2010 C63 AMG
Some dealers don't drain the oil cooler... I wouldn't be shocked if he hadn't been asked by Mercedes at some point to mention that you don't need to or recommended against it. It's not going to creat an air bubble...
