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'93 2.5 Turbo timing chain replacement interval
Recently purchased a one owner, '93 300D 2.5 Turbo that appeared to have been serviced regularly at the MB dealer from which it was purchased. The service book indicates the work was performed as outlined. However, I can not find all the receipts related to these visits.
Question: is there a general consensus or a published interval that the timing chain and related hardware should have been replaced. The car currently has ~143K and works very well. I would like to keep it that way. Suggestions/advice welcome. |
#2
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chain
Those chains are stainless steel and are dual sproceted..
i have 3 of them one with 200k Never had any problems with the 2.5's that i have heard of... |
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The chains are stainless steel? I don't know about that now.
I'd inspect the chain and guides good but the chain should be good for 250k with regular oil changes.
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Jim |
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chain replacement feedback
The replies have been very helpful. Very conscious of this critical piece of engine hardware as I also own a '99 VW TDI which has a "belt"; the max suggested interval on that item is 60K miles.
The reliability and life of a metal chain will far exceed that of a belt, just wanted to find out the range over which it should be considered for replacement. Thank-you. |
#5
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I just today looked at a "'91 300D Turbo - Blue, 178K mi, 40K on reblt eng, CD, sunroof, maintd, all rec. $7500".
Nice car, but the reason for the engine rebuild was the timing chain broke. |
#6
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I don't think it's my imagination that there are several threads on this forum on 300D 2.5s (OM602) that have had timing chain failure.
I haven't read anything on failure mode so I don't know if it's guides, tensioners or the chain itself that initially fails. Sixto 91 300SE 87 300SDL 83 300SD |
#7
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You don't replace the chain based on time or mileage. You replace it when it is stretched. There is a procedure in the manual to measure this. Up to 4 degress stretch is acceptable but I'd change it at 4. At 5 or more it should be done ASAP, and at 6-7 or more you are risking serious engine damage. At 150kmi I'd expect 1-3 degrees stretch if the oil was changed regularly, or even less stretch if synthetic oil had been used.
FYI, there were a rash of OM602 engines that had flawed chains from the factory. There was a recall on this, I forget the details, but basically you measured the stretch and if it was excessively worn in relatively low miles you got a new chain. Not sure if that still applies today... Here's the replacement procedure: http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf HTH, Last edited by vstech; 09-25-2011 at 11:31 AM. |
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I have a 91 300D 2.5 with only 77K original mileage. I checked the chain for stretch a couple of weeks ago and was astonished to find that it currently has 5 degrees of stretch. This measurment was taken using the factory procedure at 2mm of valve lift, not the old "line up the marks" approach. I'm really surprised at this amount of stretch since the car came with records indicating oil changes every 4-5K miles.
I did look up the factory recall on the 602 chains - it was in a Star issue a couple of years ago. As I recall it applied to early versions of the 602.962. My 91 model was NOT in the recall so I can say that maybe you should at least check the chain for stretch since it would appear that at least some examples of this engine DO seem to have chain stretch issues. I also agree with Sixto, I have heard (second and third hand) about some chain failures with 602 engines. I'll be doing the chain in my car as soon as I can get the time. Tim |
#9
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FWIW, when I replaced my head I checked chain stretch multiple times. First I set the TDC pointer with a dial gauge on the piston crown (it was 1 degree off, 3 degrees total adjustment range). Using the "line up the marks" method, after 4 or 5 tries, I read 4 degrees stretch each time. I then used the dial gauge on the lifter method with 2mm lift and got the SAME result each time, 4 degrees stretch. That convinced me that the "eyeball" method was close enough for a quick check. I also plan on replacing my chain very soon (the car is parked for the winter anyway and isn't being driven until I do the chain!)
But yeah, 5 degrees is excessive at 77kmi! Wow. Marshall Booth says a new chain with synthetic oil have near zero wear, even over 100-200kmi. Also check your sprockets closely, replace them if they are worn. I do highly recommend buying the chain loader tool, as described in the PDF file above. It's fairly cheap at ~$25 or so. It makes the chain replacement a 1-person job with no creative bungee cords needed! Regards, |
#10
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Quote:
Is the problem known to be a bad batch of chains? FastLane shows the same internal part numbers for the chains and tensioners of the 300D 2.5 and 350SDL. Does anyone know if the originals had the same part number or if there's been a change to either chain spec along the way? Sixto 91 300SE 87 300SDL 83 300sD |
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The initial problem with bad chains was a quality control issue from the chain manufacturer, not a design problem with the chain itself. MB dicovered the issue during production and corrected it. The chain part number remains the same. I forget the rest of the details...
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#12
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The bad chains were in 1993 model year 300D 2.5 turbos. I think there was a specific range of chassis numbers affected, not the entire year's production.
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DavidB29 1992 300E with ASR 35 years of Diesels until now! |
#13
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Information from DavidB29
My anxiety level has just gone up a notch. Given the age of the car, 1993, mileage ~144K and no indication of chain replacement in the records, I am starting to worry more.
How co-operative are dealers to assist owners wanting to make inquiries about archived re-calls? I am only guessing but the correlation of chassis number and defective chains must exist on some form of database. Am open to any suggestions. I will have it changed shortly but knowing it was not on the "hit list" would be re-assuring. Thank-you. |
#14
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The "stretched" timing chains of 1993 engines are discussed in Mercedes-Benz Technical Service Bulletin Ref 05/91 dated December 1994. The heading says it applies to engines 602 and 603 in chasses 124 and 140, cars built between July 1992 and July 1993.
The bulletin indicates that affected engines may indicate one or more of the following: unusual noise form chain area, rough running, hard starting, loss of power, increase in oil consumption. There is a list of specific chassis numbers in the bulletin. I have a copy I downloaded from Alldata. The chassis numbers are somewhat difficult to read but appear to be as follows: For model 124, engine 602: from B810470 to B999999 from D000001 to D025898 from J001335 to J01979 from F231885 to F266917 In the above list, the "D" could be a "C," it is very tough to tell. for Model 140, engine 603 from A092142 to A155557 If in doubt, I would ask your MB dealer to check the bulletin for you. The bulletin says that the chain should be replaced if the stretch exceeds 3 degrees. In that case, the timing chain sprocket is to be inspected. If the sprocket teeth are broken or worn as shown in the bulletin figures, the camshaft sprocket and injection pump timing sprocket are to be replaced. If the stretch exceeds 10 degrees, the pistons are to be inspected for damage. The Bulletin does not indicate the warranty aspects of this. That is, it does not say who picks up the tab. Hope this helps!
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DavidB29 1992 300E with ASR 35 years of Diesels until now! |
#15
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CORRECTION
Second number in J series of chassis numbers in my previous post should have read J019179. Sorry for error. David B
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DavidB29 1992 300E with ASR 35 years of Diesels until now! |
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