Even if the 14 cracks, if your machinist knows what he's doing they can be welded. I do it all the time and there are members on this forum that are driving around with my welded heads for years.


For what it's worth, it's not a matter of preservation - the head WILL crack and has most likely already started. The expansion tank cap in PROPER working order and preventing overheating will postpone your head removal. I think the lowest mileage 603 I've pulled apart had 27k on it, and it was already cracking at the prechamber.

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Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....

Again, a pretty broad/sweeping generalization that's pretty unfair. Why would the head come off a 27K mile car unless there were problems? If it cracked that early (and that's why the head was coming off?), it would indicate a manufacturing defect, not a design fault.



The head came off my SDL for valve work at 173K on the odo (no idea what the actual mileage was since the odo had stopped) and had zero cracks, zero warpage, and still had the factory head gasket fitted.


They can last if looked after. Sure the later castings are stronger, but there are enough 14 heads out there running that says they're better than people like to think they are.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

A few things I have observed over time. Control of the alloy used in casting may have ben poor. One member did several hardness tests some years back. The tests showed a substantial difference in Rockwell hardness numbers. Between 603 heads.

Plus most have used these engines like non turbo gas engines. Letting them run a minute or so before shutting down does tend to equalize hot spots. The coefficient of expansion and contraction is substantially greater than with cast iron. So if hot spots boil off the stresses will be substantionaly more and over time can take their toll. .

Also there is the turbo bearing and seals to consider. As soon as you shut down the cooling effect of the oil flow is lost. Some of the latest Volkswagon gas cars have added an electric oil pump that cycles on for a minute when you shut the engine down. To service the turbo and bearings by absorbing heat.

If people persist in not observing the requirements of tubo engines from an operational standpoint. Especially those with lets say inherent weakness issues. There is a price to pay in longevity. This also is a good practice with even the all cast iron engines.

It is a hard habit to develop. Plus there is no certainty. At the same time leaving the engine at idle before shutting down is not going to hurt anything. Especially after a highway run.

Driving up to a fuel pump when just pulling off the highways. Shutting down right away to refuel is perhaps about as abusive of a diesel engine as possible. Instead hang back and let the engine idle for a minute of two before pulling up to the the fuel pumps and shutting down to refuel.

For the cost of the additive a water wetter agent might also be considered. Every attempt to prolong may be a failure at the same time. As these engines do not even appear to like moderately high operational tempertures. This to me also is an indication that hot spots may be boiling off during normal operation. As was mentioned by an earlier poster.

If this is the case another contributor is. Test your rad cap for its release pressure. A low pressure cooling system just might have a little influence on those hot spots. Higher coolant pressure may reduce the extent of boiling off hot spots to some degree. Again this is something that is far from certain.

There are other reasons to not want a tired radiator cap with age. So you can get them tested easy enough. If I did not have a pressure tester I can see a garage doing this for me for free. Or a rad shop. It may be fine but untested there is no assurance it is. You just take your radiator cap in.

Thanks to all so far and happy holidays, good info!

Sixto, Yes, I do like the sound of the OM603, it's satisfying.

31 years and no problems with #14 head. Original owner.