my turn for the OM603 cracked head syndrome
 

It would appear that is my turn to deal with the infamous 603 problematic head. During my 60 mile 1 way commute, my 87 300D started to emit white smoke, at which point my rear end began to pucker as I glanced down at the temp gauge and it was about 5 millimeters from the red, I was on the first of 2 bridges I cross, in heavy traffic, when this all started, and I decided to get it to the top of the bridge where I could coast it to a rest stop. After sitting for about 30 min with the hood vertical, I turned on the ignition. The gauge was back below 80 so I opened the reservoir. There was coolant in the tank but I topped it off with some of the gallon of water I carry in the trunk. I started it and saw smoke (actually steam) coming from the tank. I it smelled like burning antifreeze. I remembered a discussion with gsxr where if the upper hose is pressurized after a very short while when the car is started, that there is a problem with the head gasket and/or head. So I capped the tank and sure enough within 10 seconds there was much pressure in the hose.

Background:
I have done several engine swaps rebuilds and repairs on American Japanese and other German cars (Porsche and VW) and am somewhat well equipped as far as tools go. I own the 124 CD owners manuals and have found them pretty useful. But I really value the input of all of your experience and wisdom; it has proven extremely useful in the past.
My plea:
Can anyone get me through some of the particulars involved with removing and replacing the head?

Dean:

There is no real difference between the OM603 head and a VW/Audi head other than the keyed sproket on the cam.

Wire tie the chain to the sproket with the engien at TDC compression on #1 and have at it.

Instructions in the manual are adequate.

You may. also, simply have a blown head gasket, but that's not common on these cars -- the syptoms of a bad head gasket are serious oil leaks at the parting line.

Other than the cost, not a bid deal. Get all new lifters, you don't wanna have to mess around doing them again later.

Peter

I think I can also shed some light, but from another angle.

It is the first I've ever heard about VW/ Audi sharing the same exact head as the 603 and while I am not aware that they do, if they do I doubt the price for a new head would be any less than the MB head.

I have been down this road too, and I priced a new head at $1900 and some change. new heads do not come with much, you have to buy nearly everything that is fitted on the head such as pre-combustion chambers, valves, lifters, cam, the $70 valve cover gasket!

I figured over $3000 to put a new head on my 87 300DT I could buy a good used MB for that money!

I ended up buying another engine that was complete for less than the price of the bare new head.

Good OM603's can be had used from prices ranging from $1500 to $2500 on average.

It is far cheaper to go this route than a new head plus you end up with many spare parts from the old engine.

peter, I thought I saw someone posting something about not letting the chain fall or something like that. Is that a big concern? also do you have any sources for a new head if need be. What about replacment of other components within the head?

No, the MB OM603 doesn't share a head with any other engine, it's just that removing cylinder head on the 603 isn't very different from the VW/Audi head (other than the extra cylinder to two).

If you can find a good used 603 you are a very, very lucky guy, whatever the price. Last time I asked around no one had one that wasn't busted. Going price was $7000 for one in running condition, too!

New head is available on FastLane, I think, and other places. Last price I saw for a bare one (brand new, the only one you want) was $2500, but they turn up now and again on eBay for about $1400. Naturally, you may not be able to wait for an eBay deal.

Peter

Are you ready for this?

Car-Part.com



'm not sure why the the above internet address does not automatically parse the URLs: but I did punch it up and the address is golden.

Gee they've gotten cheap!

Dean:

You definitely DO NOT want to drop the chain, either end. I manage to let both ends get away from me (from stupidity, mostly), and while I don't think the free end was too much trouble, other than fishing it up from the bottom of the chain case with a stick of silver solder with a hook bent in it, I don't recommend it. The other end slipped, too, and I cannot get the blasted thing to start, so I suspect the timing is now VERY late (lots of smoke and almost firing....).

A project for the next couple weekends, I really need to get all the cars running and sell a couple, I have too many!

Peter

Peter, I'm going for a hat trick :) If the chain is intact, you can let it drop into the abyss and fish it out without worries. It's not going to come off the IP timer or any sprocket. If you're worried, put back the tensioner after you pull the sprocket off the cam. That'll make it really difficult to lose the chain into the abyss.

Sixto
95 S420
87 300SDL

Can someone post a pic showing exactly where the version number of the head is stamped? I've looked but can't find it. Keep in mind that I haven't taken anything off the engine yet.

The head version number is stamped right under the crossover pipe, facing the drivers side. Mine is P603 016 14 01, is this an original head?

There was a proceedure for keeping the timing chain from dropping into the engine during cylinder head removal outlined in early Mercedes factory service manuals. After all the cylinder head bolts are removed remove the camshaft sprocket and have someone hold it up above the head to keep tension on the chain. You might get away with just removing the tensioner. Then lift the head slightly in the front and slip a stiff wire like an 1/8" welding rod beneath the head, passing through both sides of the timing chain just above the block surface. Now you can remove the sprocket and let the chain rest on top of the block. Align the engine at TDC first.

14 is the lowest number I've seen and the number found on original 86-87 heads. There's a 603 ahead of the 016 XX 01.

To localize it further, it's between the #2 and #3 injectors.

Sixto
95 S420
87 300SDL

Thanks to everybody that has posted , I know this is a common topic and kind of redundant so thanks for bearing with me.:) For the most part the head is ready to come out. I do need to get the head bolt tool , any good resources for that? or at least what size is it and what is it called? I have a really decent foreign parts store near byForeign Car parts of Groton They ship nation wide , PHONE: (IN USA) 877 634-0063 (OUTSIDE USA) 860-445-7340 FAX: 860 445-0511. They have done real well by me for most everything I've needed for my 2 87's . well enoug babbling and back to work.
Thanks again.

Thanks! I'll look closer when I am up at the farm again.

For the head bolt tool go to Pep Boys or AutoZone and get the pack of 4 12-point (double hex) bits that slip right into a 1/2" socket. I think the 603 takes the 10mm bit. The bits are strong enough for the 50-70 Nm (depending on reference) plus 2 90-degree turns the 603 tightening procedure calls for. It's ~$10 for the pack.

Sixto
95 S420
87 300SDL