Does anyone know ANYTHING about a 603 #15 head?
 

Yep, I've got a #15 head on my SDL. Apparently they're very rare. Does anyone know anything about them? Just curious...since I've got one.

afaik, all heads built above the 14 have the improved design. the higher the number, the more design changes implemented.
likely the 15 still has straight injectors.

Nobody knows anything about them.

They are an updated version of the #14..........obviously.

The details of the update are unknown.

I think the #17 hears were out by 1989 w/ the 3.5L motor.

-J

It would be nice to know if the 15 addressed the overheating issue....but apparently no one knows (yet).

............what "overheating" issue??

Head cracking if engine overheats.

Personally, I am not of the opinion that any aluminum head is going to survive a severe overheat on a 603. The design of the head with very little material between the valves and the prechamber is the primary cause of this.

While the later heads improved the design with more material in the weaker areas, it's still not cast iron and any thought that it is bulletproof ought to be dispelled.

BTW, take a close look at the belt on the SDL. It might be three years old now..........and I would change it on principle. It's a 15 minute job if you're prepared and understand the belt routing.

Thankfully, I'm a compulsive gauge watcher.

I thought I was as well.

But, you only have about 1 minute at 3000 rpm without the belt. Fortunately, you lose power steering if the belt goes............an immediate alarm!

If the belt goes do any lights illuminate? I've only thrown a belt once (on the 92 300D), but that was because the alternator went out so I'm guessing that account for the lights coming on.

Visually the belt looks to be in good shape.

You'd get an immediate alternator light as well.

I tend to believe the noise of the belt letting go and the loss of the p/s would give anyone who's got the slightest perception the notice to get the vehicle off the road immediately.

The danger lies where the driver chooses to make "the next exit". Catastrophic.

It's not me I worry about. But my son driving the 92? That's another story....

There are all kinds of examples on here of children trashing the engine due to "next gas station syndrome".

You might as well accept that fact............it will happen if the belt lets go.

The various mods from #14 through to #22 were designed to address problems involving too little material in the head between areas of relative pressure/different fluids. These weak areas tended to have head gasket failures causing coolant to be dumped into the oil pan or vice-versa. The "next exit" problem, as Brian writes, whether caused by a serpentine belt failure or by letting the coolant get low, will not be fixed by any head redesign. Alloy heads cannot survive the kind of overheating that cast iron will shrug off (and it's also possible to overheat a 61x engine, you just have to work a little harder).

Jeremy

yup. I have 2 617's with cracked heads from driving without coolant I'd guess...

A 123 diesel was in my indy's shop late last year with what they finally decided was a cracked head from driving with little or no coolant. The driver simply ignored the gauge as long as the engine kept running. The mechanic said it actually ran fairly well, considering. Last I heard they were shopping for a good used head.

Jeremy

I found a 15 in a JY years back, it was on a 3L motor (in an '86) if that tells you anything. Sold that off as I bought a fully refreshed 17 on the board with camshaft, new lifters, new springs, new injectors, etc.

Potentially I may have a few pictures of it still, if anyone cares I will look. I think it had the 'straight' injection still.

#15 head info
 

I bought an intact #15 head as a core to rebuild and replace my cracked #14. It appeared not to have been machined before it got to me. It had the collars with the splines and the newer angled prechambers. It didn't have the coolant passage near the timing chain filled in. The machinist put my old prechambers in this head so I could use my just-rebuilt old-style injectors. He has a long background machining & building Mercedes heads at a dealer, but had not put straight prechambers in a #15+ revised head before. They dropped in fine and the prechamber protrusion into the combustion chamber was within spec, but they all still leaked like crazy, which he says he has seen many times. He says he has addressed the problem before by using some kind of locking sealant on the prechamber mating surfaces and on the locking collar threads.

I haven't looked at all the prechamber leaking threads yet, so I don't know if refinishing the prechamber bore and/or adding a shim to create a better sealing surface is a better solution.