Hello Tcane

The exact service history of this car is unknown other than it was maintained at a couple of local MBZ dealerships. It was owned (literally) by a little old lady who kept it in truly exceptional condition – it is one of those original paint, unmolested ‘time-warp’ cars that was obviously garaged & lovingly pampered, which is one reason that I decided to buy it. It had 197,000 miles on it when I bought it last June. I will have to assume that the car did overheat severely at some point prior to my ownership – that would be the only explanation as to why the cylinder head gasket would begin to fail at such low mileage.

Yes, I did inspect the head gasket – you are right in that it tells quite a story. Apparently, the leakage started at the rear of #5. It seems that while the engine was ingesting small amounts of water & burning it, the resulting steam eroded the upper section of the cylinder liner on the rear of #5 cylinder. The steam ate away about 1/4 of the thickness of the liner at the very top. There is evidence of similar damage in a couple of other cylinders, but not nearly as bad. On several cylinders, the steam also ate away at the vertical edges of the aluminum sealing ring that is integral with the head gasket, so when it was removed, it seemed as if there were two separate rings – one on each side of the gasket, rather than one piece wrapping from one face to the other. The rings separated from the body of the gasket, so there definitely was inter-cylinder leakage, especially between cylinders 4&5.

Addressing your list item by item: The amount of coolant loss was not at a rapid enough rate to have caused hydraulic lock, so that is not the reason that the head cracked. The head bolts were not the cause – they are within specification for length, so I will actually be reusing them. With this vintage of MBZ, quality control should not be an issue - it seems highly unlikely that there was any casting flaw from the factory, so we can rule that out. There was not “too much boost” from the turbo – I previously adjusted it to spec, plus there is overboost protection built in by the factory (if there is too much boost, a solenoid valve opens which dumps the boost signal going to the ALDA, reducing fuel flow, effectively reducing exhaust energy & therefore turbine speed).

As I said earlier, I believe that unless this is just a fluke, the engine must have been overheated severely at some time – perhaps a radiator hose let go on granny some time ago.

I hypothesize that once the combustion gasses were able to escape into the water jackets of the head, the gasses pushed the water out of the cylinder head passages – this allowed certain localized areas of the head to become severely overheated, which then lead to the cracking. This is conjecture on my part, but again, it seems quite logical.

As far as head gasket design is concerned, there is still a significant difference between manufacturers. The first gasket that I got was a Reinz – I was NOT impressed with either the design, nor the (lack of) quality control. Needless to say, it went back to the supplier. The Elring gasket has a lot more meat to it – there is metal reinforcing between cylinders in addition to the normal sealing rings, plus it is readily visible that the quality control is better – the sealing rings are more symmetrical vs. the Reinz. I’m sure that others may disagree; some people are blindly allegiant to brands – such as is the case when people start discussing motor oils….

Thanks again for your reply… I hope that this information will be helpful for others out there.

RTH