my turn for the OM603 cracked head syndrome - Page 2 - PeachParts Mercedes-Benz Forum

HGV · #16 07-27-2004, 01:05 AM

I have done this and can offer the following tips. Replace all the plastic clips for the fuel lines, they will break and without them the tubes will eventually crack at the injector. replace all lifters. Have the head preasure tested and use special die that will glow with a black lite. the machine shop should be familiar with this. It will locate any cracks that make it throught the pressure test. have the exhasut manifold shaved to remove any high low. It will leak even on a new head. they warp. check to make sure your head bolts are not streched. When removing the cam, be careful that you follow the correct bearing cap removal sequence or you can crack the cam shaft. Mark the orientation of the chain guides. You can install them upside down. Be carefull in removing the press pins for the chain rails. They are difficult and can easily be stripped. Replace all the heat sheild seals on the injector. clean out the intake manifold before you reinstall. Use the ball hex allens for removal of the intake manifold bolts. Check that you have correct placed the intake manifold before you tighten all the bolts. I did not and missed the number six. Use new copper crush nuts on the ehaust. Prior to starting the car, crank the engine without theinjectors until fuel starts pulisng out of the lines. Make sure you properly fill the engine with coolant. I usually remove the top radiator hose and fil from there. Much safer and quicker. Repalce all conusmable parts, ie belts, fuel hoses, etc. Mark all electrical and vacuum line connections as you remove them. If you have many miles on the starter motor, replace it now. easier access. Take digital photos as you progress incase you forget stuff. Remove the aluminum heat sheild from around the battery. Not needed but makes access better and you won'tt dinge it up.

Thats all I can remember. If you need anything, I am sure Sixto or psfred will chime in with good advice.

Henry

Good luck.

mplafleur · #17 08-02-2004, 09:03 AM

Here's the part number on my '86 300SDL cylinder head.

603 016 22 01

It appears that I don't have the original head as this is a late version number. Is this a good one?

md21722 · #18 08-02-2004, 09:24 AM

That head # is VERY recent - you are lucky.

mplafleur · #19 08-02-2004, 09:37 AM

I've been searching for a half an hour for a thread that had pictures and talked about version numbers. I can't find it. I thought it showed an old and new head side by side.

Maybe I can leave the head as is and just rebuild the bottom end. It would save me some $. I already have to spend $$$ on new pistons and rings.

md21722 · #20 08-02-2004, 09:57 AM

Problem with the old heads is that they were more prone to cracking than the new ones. Visible changes are minor, limited mostly to the oil supply galley near cyl 1.

theref · #21 08-02-2004, 10:08 AM

mplafleur

I am pretty sure that if you search on gxsr (Dave M) that you will find that info either in one of his posts-or in a link to his web site.

goldenbear · #22 08-02-2004, 10:16 AM

Well, so much for my belief that if you don't overheat the engine your odds of cracking a head are nil. My car started emitting white smoke from stoplights and signs Friday afternoon. Upon checking the basics I learned that both oil and coolant levels were low. My indy can't see it for another week, so I'll wait for the confirmation and post back. In the meantime, I'll be driving my f-i-l's '98 e300 dt.

theref · #23 08-02-2004, 10:43 AM

Make that GSXR

sixto · #24 08-02-2004, 11:46 AM

Quote:

Originally posted by goldenbear
Well, so much for my belief that if you don't overheat the engine your odds of cracking a head are nil. My car started emitting white smoke from stoplights and signs Friday afternoon. Upon checking the basics I learned that both oil and coolant levels were low. My indy can't see it for another week, so I'll wait for the confirmation and post back. In the meantime, I'll be driving my f-i-l's '98 e300 dt.

I'm giving some BDTD advice to a fellow who happened upon an 87 300TD with a -14- head and coolant pressure problems. He got the head off last week and determined that it's just a bad head gasket. Nonetheless he has a -22- head ready to go.

Sixto
95 S420
87 300SDL

goldenbear · #25 08-02-2004, 12:42 PM

Sixto,

In my case, the head gasket was replaced with the updated version in 2001, so I'm assuming it's the head. I don't seem to have built up pressure in the system (soft upper radiator hose), but I don't believe that symptom must occur for the head to have a crack. Please correct me if I'm wrong.

sixto · #26 08-02-2004, 08:29 PM

Mixing of oil and coolant sounds like a head gasket to me. When the head cracks, the cracks go in a variety of directions like to the valve seats and coolant passages. The heads don't crack between coolant and oil passages, at least it's not a likely first crack propagation. If mixing oil and coolant is the extent of your symptoms, I'm inclined to think it's just a head gasket. In my case, I had pressure in the cooling system but no mixing of oil and coolant. The cracks were easily recognizeable at the point I pulled the head and again, no mixing of oil and coolant.

Besides, if you're me, the first thing you suspect is the last thing you touched

Sixto
95 S420
87 300SDL

gsxr · #27 08-03-2004, 03:50 PM

ok - there are a lot of points to cover here, hope I don't miss any:

1) Mixed liquids is probably a bad gasket - not likely to be a crack. High cold pressure usually means a cracked head, but ONLY if the cooling system is 100% leak free. Otherwise the pressure leaks out. Loss of coolant can mean advanced failure, and bubbles in the expansion tank also mean advanced failiure (i.e., a big crack). Let it go too long and you can get hydrolock, possible bent rod from the hydrolock, or steam erosion from water entering the combustion chamber (requiring a new/used short block.) If the engine is "burning" cooling, STOP DRIVING IT!

2) The part number is 603-016-xx-01 where "xx" is the revision. 14 is the original, weak head. 17 is the first "good" head, used on all 3.5L USA engines from 1990-95. There was a 20 head available for a short time, which was replaced by the current 22 head you would buy new. mplafleur's head is the latest which is very lucky for him. (There is also a rare 15 head, only been sighted once, and nobody is really sure if it is the "weak" version or not.)

3) Henry's tips are excellent. I'd add to also replace the plastic expansion tank (the new type adds a silica pack to control corrosion), and only use MB antifreeze, or Zerex G-05 (which is the same thing.)

4) I bought the OE Hazet head bolt tool, it was under $20. You'll swear something is about to break when you try to loosen those head bolts - make sure the drive bit is FULLY seated before you start applying major torque.

5) New heads are bare and will re-use your old valves & springs. You need to buy new OE dealer (not aftermarket!) valve stem seals. This requires a special spring comressor tool (not rented at AutoZone), so either buy the tool ($200), or better yet pay a machine shop to swap valves/springs/seals.

6) Buying a used #17 head from a 3.5L is a viable alternative, however plan on getting it checked at a machine shop, and installing new seals. If it needs a surface cut, the prechambers may need to be shimmed up, and the shims are ~$100/set!

7) Current wholesale price on a NEW head is about $1600. Used heads are in the $800-$1200 range, but may include cam & lifters, which means you can pick through 24 used lifters to get 12 good ones and save $300+ for new ones (if you're on a budget.)

8) Don't install a crack-free 14 head unless you don't mind repeating the whole 20-40 hour job a second time.

9) New prechambers are not required. the stupid WorldPac note about needing new PC's is wrong and pisses me off because it misleads a lot of people. Your new head may work with the old prechambers, or may not. If not, you need to modify the PC's (mill them slightly) to seat correctly. Or, you can convert to the inclined/angular injection, which will fit without modifications, but costs $1000-$1500 new and is obviously not worth it. This may be a viable option if you buy a used #17 head that includes all the inclined injection parts. Some people are lucky and bolt in old PC's with no problems.

10) Buying a used engine to "save money" is false economy. If it comes with a #14 head, which is almost guaranteed, you will have the SAME failure in the future. The solution is a new head, #17 or above, to prevent the problem from coming back. Buy a used 603 engine if you throw a rod through the block, or something like that.

11) If anyone needs to buy the prechamber removal tools - slide hammer, and lock ring pin wrench - send me a private email. I was working with someone on making good-quality versions of these at decent prices. The side hammers are available for sale now, the pin wrench should be available in the next week or so. I'll be posting more info in the "classified" section shortly but thought I'd give some early warning to those of you who might need them. These are Made in USA, top quality, heat treated, zinc plated... nothing like the Taiwan junk sold by Sir Tools (and Baum, Performance Products, etc who carry the ST crap.)

HTH,

Habanero · #28 08-04-2004, 08:25 AM

Add me to the list of recently cracked heads. I have had cold pressure in the cooling system for a while, then just recently started using coolant. Found out yesterday it was indeed a cracked head. I just bought this car a year ago, but since I have had it there has been no overheating issues.

gsxr · #29 08-04-2004, 10:16 AM

Ouch - sorry to hear that, Habanero.

Let us know what you end up doing for the repair, and also the cost... I'm trying to keep tabs on the failed 603's. It seems there has been a good half-dozen failures in the past couple of months!

Habanero · #30 08-04-2004, 10:59 AM

The indy is having a machine shop weld the head. I am a little nervous about it, but they said they have had literally dozens repaired that way over the years with no problems thus far. Unfortunately I just moved to a house with no garage and my tools are 3 hours away so I had to take it to an indy for the repair.First time in my life I have taken a car to somebody outside the family to fix (Dad and 2 brothers are mechanics, but 8.5 hours away).