603 head RR, is it a DIY job? - Page 2 - PeachParts Mercedes-Benz Forum

winmutt · #16 01-24-2011, 12:19 PM

Quote:

Originally Posted by billhard

Ok I'll try it. I found another #14 head on the forum here:

FS OM603 Injection Pump, Turbo, & Cylinder Head (plus other parts)

I am kind of thinking this sounds good since this car isn't exactly a pristine example of a w124. Should I search out a higher numbered head?

I believe my Car is a 603.96, will any other heads do? For example 603.97

No way would I do that amount of work with a known bad part. Its not if the #14 is bad, they all are. All it takes is an overheat and you are back to square 1. All the ones above 14 still had issues until they got it right with #22. They just kept making them better and better. I would shoot for 17 or higher. I bleieve 18 and up (18 being the changeover and is a mixed bag) have the oblique angle injectors requiring different injectors and piping (I believe the piping can be bent). These could be found on the NA 1995 e300D and up.

babymog · #17 01-24-2011, 03:25 PM

The '95 NA engine is a 606, completely different head and not a bolt-on change. Further, it is important to only use a turbo head on a turbo engine, covered in the link at the bottom.

The heads don't all seem to fail, I've not had a #14 failure out of 3 owned, others on this forum have seen 350k, 500k, without failure.

Nobody has (yet) determined the cause of the failure, it has been suggested by many that it is overheating, I suspect other things like inadequate process control by the head casting supplier combined with a head design that wasn't robust enough to handle the variatioins in the casting process, which would suggest that some heads will fail no matter how well cared for, others will not. As an automotive Engineer, I've seen many situations where the design is perfect, but the production process was not considered.

Overheating will (can anyway) kill any head, #14 or #22, aluminum or even cast iron, there was recently a discussion of a irrepariably warped 617 head from overheating on this forum.

Would I bet my life on a used #14 casting? No, but I'm not building an airplane. Would I be willing to put a #14 on a car for a repair if the head is good? If the savings justifies it, yes. With the changes also made to the original head gasket (some gaskets never failed), a new gasket could also be one key to keeping a head healthy.

I am the seller of the aforementioned head. I am not here to push anyone into buying it. I've never replaced a head on any of my 300Ds, never felt a need to, but this time I want to try a few things involving more boost and fuel (heat and pressure), have already bought the #22 head, and am kind of a "why not" guy so I'm going to do it. If the OP can find a #17 or later head (yes #17 was superceeded for a more robust design also) and is willing to pay the difference, or buy a new #22 head along with all of the necessary machining or injector/pre-chamber/injector/etc. parts to make the swap, go for it IMO, I'm not offended as I'm doing the same swap just for "fun". New this will run you IIRC around $3000. If you're patient, later castings do come along for bargain prices occasionally, timing is everything. Buying a used head is a gamble (including a used #17-#22), as is doing the work yourself, if the savings justify the work then it's a go.

Is it a DIY? The most important part IMO is proper head torquing, which is covered in the FSM, and proper cleaning of the head & block mating surfaces. If this isn't done properly, you'll blow the head gasket and be pulling the head again to replace the gasket (bad day). It is probably a weekend job, one day to remove/prepare/clean, one day to install and send someone for the part or tool that you forgot, do fluids and "while I'm in there" stuff, and get it fired up. I wouldn't plan a long trip for the car the next day, just in case something crops up that could use attention, or something doesn't seal well, etc. It happens.

If you're going to replace everything you touch while you're in there (lifters, timing chain/gears/guides, water pump, thermostat, DV seals, injectors, glow-plugs, hard-lines) it's already looking like you'll be in over the car's value and might as well put out for a new head.

OM602 & OM603 Cyl. Head Revision Reference has what information I have so far found in the FSM regarding changes to the 60x series heads.

Best of luck whatever direction you choose.

ashedd · #18 01-24-2011, 04:05 PM

What babymog said. He is very wise.

My 14 head seems perfectly fine.

winmutt · #19 01-24-2011, 05:48 PM

Quote:

Originally Posted by babymog

The '95 NA engine is a 606, completely different head and not a bolt-on change. Further, it is important to only use a turbo head on a turbo engine, covered in the link at the bottom.

Yes I misspoke myself there. I meant the oblique angle injectors could be found on those engines (cheapish replacements). I believe the injector hard lines swap as well.

I disagree with your statement, I believe all the number 14's are bad, but dont all fail. I've sent an email to Tom at Classic Parts to see if he can point us in the right direction for getting real answers (TSBs etc). FWIW http://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/70003.pdf covers the changes.