I've recently come across some unsubstantiated information that would imply that the 6 cyl diesel in the 1986/87 300SDL (and others, I presume) has a less than stellar history in terms of cylinder head integrity. According to the information I have read, cylinder heads on these engines are prone to developing cracks. Are there any Mercedes shop owners/techs in this forum that can enlighten me?

I have seen my share of cracks on the cyl head and between the cyls. Also the rods will bend if the engine ever gets a big gulp of carbon from the EGR.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Wow, that's not such good news to hear. I'm surprised that a weakness of this nature could be allowed to leave Mercedes' engineering department. As far as cylinder head cracks, I suppose there's not much anyone can do about that. As for the carbon issue from the EGR valve, do you know of an additive that can be added to the fuel that will control deposit formation? I have had good success in gasoline engines with BG44K. Is this additive suitable for use in diesel engines? Do you know of one that is and works well? Lastly, what indicates that the rods have been compromised by carbon chunks. Will the engine develop bottom end noise?

[This message has been edited by JDEN (edited 05-18-99).]

Do the '85 SD's have this problem with cracking? Other that 6 cylinder vs 5 cylinder, what other comprimises did MB make with the SDL. I own an '87 and hear that the convential wisdom is that the 603 is highly durable.

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Mark Herzig
1992 500E (82,000 miles)
1987 300SDL (105,000)

Benzmac:

Can you give me an estimate on the percentage of 603 engines you see with the cracked head/bent rod issues? Is there a mileage point where these issues become increasingly more likely to rear their ugly heads?

Thanks in advance.

The 1985 was one of the best of the crop. If you keep them maintained they will last a literal lifetime! (617 engine)

As for the later 6 cyls (603 engine), they were reliable as long as they never got too warm and the oil pump drive did not fail!! If the engine ever overheats the original head will crack! This was a big problem because the radiator necks loved to break off and loose all of the coolant at speed and the engine would overheat befor the gauge showed it! I have seen owners put a bb in the line that goes to the EGR to stop the formation of carbon in that area. (It was caused by turbo oil seepage from the front seal going by the EGR gases and harding.) I DO NOT ENDORSE THIS BUT I HAVE SEEN IT WORK BECAUSE IT CHANGES THE EMMISSIONS OF THE ENGINE AND THAT WOULD BE ILLEGAL FOR ME TO DO! :)

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

The 1986/87 cars suffered from the over-engineered emission systems, high failure Trap-oxydizer. If the engine over heats the Aluminum head can crack!!(temp gauge is standard equiptment)! Also the car has low coolant lamp! 1990 + later engines seem like they are somewhat more fragile, oil consumption & bent rods. Nobody is perfect.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH

In researching this myself because I was going to buy one ( 92sd), it seemed the problems where before this year.

What seemed to bug most people is the lack of responce benz showed.

This I know from past dealings with them.

by the way, what is a 98300Td engine series called?

What preventative measures, including
parts replacement, would the experts
recomend?

New Parts?
Radiator
Water Pump
Radiator Hoses
Thermostat
Oil pump

Procedures?
Radiator Flush
Redline "Water Weter"
Let engine cool down after hard run,
before shuting down.

Thanks !!
Another 300SDL Owner

I guess I'm confused on what can cause the engine to overheat other-than the obvious low coolent. Seems like annual radiator flushes might mitigate the clogging problem? The other suggestion of temperature gauges and low coolant indicators are the protection against overheating. Did the '85 D/SD's have an alluminum head? With the trap ozidizer removed, doesn't that put the 603 engine in the same emmission class as the '617's?

The OM603 is a good engine, but if there is any cooling system failure && the driver keeps going FORGET the engine!
The OM617 engine has a cast iron head. Somewhat more forgiving, but they can fail also.
The W140 chassis diesel weighed too much for the size of the engine. Oil consumption is common & other(non-diesel) failures are somewhat common.
The 1998 E300DT is a OM606 engine.

What's a BB? How can I prevent the oil pump drive from failig? Is that eay to change or how much mileage before I change it so it never fails.

How do I prevent the radiator necks frmo breaking?


Francis

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Benzmac:
The 1985 was one of the best of the crop. If you keep them maintained they will last a literal lifetime! (617 engine)

As for the later 6 cyls (603 engine), they were reliable as long as they never got too warm and the oil pump drive did not fail!! If the engine ever overheats the original head will crack! This was a big problem because the radiator necks loved to break off and loose all of the coolant at speed and the engine would overheat befor the gauge showed it! I have seen owners put a bb in the line that goes to the EGR to stop the formation of carbon in that area. (It was caused by turbo oil seepage from the front seal going by the EGR gases and harding.) I DO NOT ENDORSE THIS BUT I HAVE SEEN IT WORK BECAUSE IT CHANGES THE EMMISSIONS OF THE ENGINE AND THAT WOULD BE ILLEGAL FOR ME TO DO! :)

<HR></BLOCKQUOTE>

francis -

BBs, (ball bearing) as those you shoot out of a crossman air rifle. Or something similar that would fit inside the vaccuum tube to cause blockage.
This seems to look less obvious then the outright removal and plugging the end of the vaccuum line, which is illegal.

I believe the crack-prone radiator hose necks were later reenforced with a metal sleeve inside.

[This message has been edited by VA300SD (edited 02-12-2000).]

Francis,

In another post I saw that you wrote that your car was an '85 300D. (not SD) This indicates to me that you have a 617.95x motor (5cyl.) The other engines mentioned are all 6cyl.

I thought I would mention this to you so you can shorten your list of things to "worry" about. :)

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03/83 300D
07/73 280

Larry,

I have an 85' 300D (Euro) 124 body. It's 6 cylinders. The 300D first came out in 1985 for the Euro an 1987 for the US Version (Turbo).


Francis

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Larry Delor:
Francis,

In another post I saw that you wrote that your car was an '85 300D. (not SD) This indicates to me that you have a 617.95x motor (5cyl.) The other engines mentioned are all 6cyl.

I thought I would mention this to you so you can shorten your list of things to "worry" about. :)

<HR></BLOCKQUOTE>