OM603 Cracked Head - What else to change? - PeachParts Mercedes-Benz Forum

goldenbear · #1 08-02-2004, 01:52 PM

Sadly, my car began showing signs of a cracked head on Friday. It will get in to my indy's shop early next week. For now, I'm interested in learning, ideally, while the engine is apart to replace the head what else should be replaced. I also plan on replacing the lifters, and maybe the chain. Anything else? Prechambers? Cam? If replacing something would be a waste of money, I'd appreciate those thoughts as well. Thanks.

Brian Carlton · #2 08-02-2004, 02:19 PM

Damn, my condolences. This really has me concerned now. Two members with cracked 603 heads this month. Any indication of distress or just shows up out of the blue? Which casting number?
No overheating?

I've got to do a head gasket on the 617. The 603 head situation is much worse.

Dave (GSXR) is the resident 603 expert. You might e-mail him for a detailed list of suggestions.

goldenbear · #3 08-02-2004, 03:46 PM

Thanks, Brian. I'm hoping he'll chime in. I've followed his posts for many years.

No signs, normal operation, no overheating. This is disappointing, because I firmly believed that by watching it closely and maintaining it wisely that it would last. It is the original head, "14".

Brian Carlton · #4 08-02-2004, 03:55 PM

It is the strangest thing. Hatterasguy was at the get-to-gether with the SDL. He has over 220K on the same 14 casting.

goldenbear · #5 08-02-2004, 04:08 PM

Yep. Quite contrary to my post just 4 days ago in this thread: W124 Diesel Aluminum Heads.(87 300D)

gsxr · #6 08-02-2004, 04:34 PM

My condolences as well.

For the record, if the car had *at any time in the past* been allowed to get hot, the crack can start... and then "finish" much later. My blue car had this happen. It got very hot once in 1999 or so, due to a burst hose. No problem after fixing the hose. Then in late 2001, a few YEARS later, the high pressure symptom suddenly appeared - and it had not been over 105C for those few years! Go figure.

It also spent a lot of time in the 105-115C range in summer of 1998 while I chased down the cooling problem (the 4-year old radiator was bad, imagine that - new one cured the problem.) I do not know if the car had been overheated by the previous 2 owners, but I know it still had the trap installed when I bought it in summer 1997, and I know it had ZERO pressure in the upper hose when cold all the way through fall 2001 when the problem suddenly appeared.

Anyway - what to change out kinda depends on your wallet, how long you plan to keep the car, if you are DIY or paying a mechanic, etc. I can say that prechambers and camshaft do NOT require replacement unless they are worn or damaged, which is rare. All new lifters are nice but expensive... ~$25/each. Keep the old lifters as spares, or try to test them & at least keep the good ones. Check timing chain stretch before starting the job, if 4 degrees or more, replace that too. If 3 or less, you can leave it alone to save $200+. At 2 degrees or less I'd definitely leave it alone. You'll need a new upper chain rail (cheap), and need to inspect the usual items... serp belt tensioner, vac pump drive cam (if vac pump is removed), etc. This is a good time to replace the right side engine mount because access is easy with the head & turbo removed. If your IP is leaking oil, it's also a handy time to yank that and re-seal it ($30 in gaskets plus a few hours R&R and rebuild time.) New head bolts may be required if the old ones are stretched past spec (not likely). Only use OE dealer valve stem seals! Using the OE dealer head gasket set is also highly recommended. See if your indy will let you supply some of the parts & gaskets. And make sure he uses MB coolant when done. Oh yeah, install a new plastic radiator tank, the new ones have a silica pack to control corrosion, and your old one is probably yellow, nasty, and brittle, with hidden cracks on the backside like almost every other one I've seen over 10 years old.

I think the biggest question for you is if you want a new head, or a used (#17+) head. New are $1600 current wholesale, bare. Used are about $900, usually with valves & springs. Figure another $250 for a machine shop to install your new OE valve seals and swap your old valves into the new head (or check out the used head/valves/etc and install new seals). I can send the name of the machine shop that's probably the most experienced in the USA with OM60x heads, if you are willing to send the work to CA. It's the shop that does all the machine work for Metric Motors, the MB engine rebuilder.

Best regards,

goldenbear · #7 08-02-2004, 04:49 PM

Quote:

Originally posted by gsxr
For the record, if the car had *at any time in the past* been allowed to get hot, the crack can start... and then "finish" much later.

This makes sense, and may give others hope with the original head. I know for a fact the PO, my f-i-l, briefly overheated the engine after his serp belt snapped in 105F heat in 1996.

Quote:

Anyway - what to change out kinda depends on your wallet, how long you plan to keep the car, if you are DIY or paying a mechanic, etc. I can say that prechambers and camshaft do NOT require replacement unless they are worn or damaged, which is rare. All new lifters are nice but expensive... ~$25/each. Keep the old lifters as spares, or try to test them & at least keep the good ones. Check timing chain stretch before starting the job, if 4 degrees or more, replace that too. If 3 or less, you can leave it alone to save $200+. At 2 degrees or less I'd definitely leave it alone. You'll need a new upper chain rail (cheap), and need to inspect the usual items... serp belt tensioner, vac pump drive cam (if vac pump is removed), etc. This is a good time to replace the right side engine mount because access is easy with the head & turbo removed. If your IP is leaking oil, it's also a handy time to yank that and re-seal it ($30 in gaskets plus a few hours R&R and rebuild time.) New head bolts may be required if the old ones are stretched past spec (not likely). Only use OE dealer valve stem seals! Using the OE dealer head gasket set is also highly recommended. See if your indy will let you supply some of the parts & gaskets. And make sure he uses MB coolant when done. Oh yeah, install a new plastic radiator tank, the new ones have a silica pack to control corrosion, and your old one is probably yellow, nasty, and brittle, with hidden cracks on the backside like almost every other one I've seen over 10 years old.

Thanks for the detailed info. I'll follow your advice. My indy will be doing the job; I don't have the time or patience. I plan on keeping the car a long time and money is not an object; I want it done right! Fortunately, a lot of the items have already been replaced: vac pump in 2002, serp belt tensioner in 2001, IP in 2001, head gasket in 2001 (though I'm sure I'll need a new one). Good suggestion on the plastic radiator tank.

Quote:

I think the biggest question for you is if you want a new head, or a used (#17+) head. New are $1600 current wholesale, bare. Used are about $900, usually with valves & springs.

Thanks again for all the input. I'll definitely be getting a new head. It gets in the shop on 8/10 - I'll keep you posted. Perhaps the only upside to this is I'll be driving my f-i-l's '98 e300 dt in the interim.

Brian Carlton · #8 08-02-2004, 06:13 PM

Quote:

Originally posted by goldenbear
Carrameow,

Note that if you have the original head it doesn't mean that it WILL crack. I know upwards of a dozen OM603 owners with the original head, one of them is shooting for 500k mi by the end of this year (currently at 472k mi). Just watch your temp closely and don't allow it to overheat. Replacing the trap oxidizer should be a priority.

__________________
Chris

This is spooky. Almost like the 603 heard you

Hatterasguy · #9 08-02-2004, 06:21 PM

This is strange I was under the impression that 603 heads would be fine unless really overheated like 120+(red zone). Mine never runs hotter than 90-95 and seems fine. I'll be rolling over 237k this week on the original head. Plantman has 330K+ on his!

Brian Carlton · #10 08-02-2004, 06:28 PM

Hattie:

Quote:

Originally posted by goldenbear
I know for a fact the PO, my f-i-l, briefly overheated the engine after his serp belt snapped in 105F heat in 1996.

That will do it.

Hatterasguy · #11 08-02-2004, 07:00 PM

Fastlane says you have to change the pre-chambers (I think).

dieseldiehard · #12 08-02-2004, 07:31 PM

I reused my old PC chambers after wire brushing them and inspecting them closely. I did however use new head bolts, some mechanics re-use them

One thing that wasn't discussed here yet however is OE vs. aftermarket heads. There are some aftermarket OM603 heads around that have a small lip that was not machined properly in the PC openings.
GSXR ran into this problem and had to machine his chambers to fit.
See my post on the thread by Carrameow re: 87 aluminum heads that describes this.
DDH

gsxr · #13 08-02-2004, 07:43 PM

The prechamber issue affects some newer heads - possibly #17 or #20 as well, definitely some #22, since it happened to me. Aftermakret or OE, it doesn't matter, they both can have the problem - trust me. Metric Motors says they find it on maybe half the new 603 heads they buy when rebuilding 603's. Some need machining, others don't. Apparently the design spec changed on the newer heads for the angled injector prechambers or something. Only way to know is to insert the p/c with the head off, measure protrusion, then insert a shim of known thickness (say, 0.5mm) and measure again, the difference should be 0.5mm - if not, you need to machine & repeat the measurements until they come out correct. Or after the head is installed and you get the nice "puff puff puff" when cranking (like I did!), yank the p/c's, machine them, and reinstall!

Note: New prechambers will do NOTHING. The note from FastLane is actually from WorldPac and is WRONG. I bought new p/c's, they didn't work either! So I milled my old ones and returned the new ones. What will work is converting to the late style angular injection - new angled prechambers, new splined lock rings, and new angled injectors - very, very expensive conversion (then you get to bend the metal injection lines to fit.)

dieseldiehard · #14 08-02-2004, 07:47 PM

Oh yes, no one mentioned the water pump but it's a good time to renew it, too
While having the head resurfaced and all the things GSXR mentioned, I got into fixing a few nuisance items that cause oil leaks, I replaced the oil filter cannister gasket (stand gasket) oil reservoir gasket, lower pan gasket and front crank seal.
And if the oil cooler lines are showing any signs of leaking this is a good time to replace them (but yikes! why are they way more expen$ive than any of lines used on 617 engines?)
Now have no more oil leaks (except the PS low pressure hoses which I replacing next week)! I think the reason the PS hoses are leaking is because the PO may have used silicone fluid.
DDH

dieseldiehard · #15 08-02-2004, 07:53 PM

wow! just 4 seconds between our posts, Dave! never had a blink like that!
I think its better (well, cheaper) to machine the head to suit the old style PC compared to new PC's, at something like $90 a pop? if ones old chambers are fine. Someone also said the new heads are not precisely smooth the way we like them to be, I think it was HGV? so might be better to have a new head skimmed and the step in the PC openings machined all at the same time.
DDH