But....cam timing is directly related to the length of the chain.

First you do the 2mm valve lift method, THEN you determine if the chain needs replacement.

Danny

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Yes but the length of the chain is NOT directly related to cam timing. At 12* he is right past the acceptable worn in limit, a woodruff key is perfectly acceptable. Otherwise MBZ would not have made offset keys eh?

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I disagree. If he is "right past the acceptable worn in limit," he is past the limit and should change the chain. IMO, even if he's 2/3 of the way to the limit, he ought to change the chain if he plans on keeping the car. A worn chain is tough on the sprockets, and is more likely to fail catastrophically.

I also "suspect" that part of the reason for offset keys is to handle production tolerances and resurfaced heads. Not a band-aid for putting off the inevitable replacement of a badly stretched (worn) chain.

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1987 W201 190D

Either the oil has not been changed frequently enough or the chain has been in service too many miles in my opinion. Fatige probability is too high to ignore. Even though there is a cost involved in you changing the chain the alternative has too much risk attached to it.

That chain may go another 100k for all I know. If it does not. In the he majority of events you are going to lose your engine. Of course read the archives and inspect your chain rails etc as well. As another member mentioned verify the exact amount of existing stretch properly first.

He is 1* out of spec for cam timing for a used chain. He is not past the limit and should replace the woodruff key PER the FSM. The FSM states that the chain should be replaced due to *excessive* elongation of the chain and that otherwise a woodruff key should be used. Woodruff keys are available for correction up to 10* at the crank meaning 5* at the cam. He can get many years of service out of the existing chain with the smallest offset of 2* at the cam.

The point here is that the woodruff key is cheap and less likely to fail than the new chain and crimp of unknown quality. If it ain't broke don't fix it, that's my 2 cents.


I suspect the FSM would have mentioned this as they mention these types of things in other sections of the manual. No reference to resurfaced heads or "production" tolerances. Believe me MBZ isn't building engines that need woodruff keys from the factory.

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I don't understand your logic about not being past the limit. I do not have the FSM for that engine, so I cannot read it myself, but it seems to me that if the largest offset key cannot bring the cam timing back to zero, then the chain suffers from "excessive elongation." Regardless, if it were my car I'd feel more comfortable knowing that I had a new chain. I'd do my research and make sure I had a quality chain and a proper crimp.

As an aside, many years ago I had a job interview at MBNA. I'm a mechanical engineer, and I was interviewing for a position that was related to US support on automatic transmissions (not that I knew a damn thing about them at the time). I went into the interview with a great deal of respect for MB, especially with how I felt they provide exemplary support for legacy products. I was pretty shocked to find an attitude during my interviews that their focus was almost entirely on keeping everything good during the warranty period. It seemed like the level of concern went down about 95% after that. As a result of that experience (and also seeing the generous wear limits and specifications of other manufacturers over the years) I now take a lot of what the FSM says with a grain of salt. Again, common sense and reference to a large experience base such as is available on this forum are key. So, if the FSM says 10 degrees of stretch is OK and correctable with a key... I'd tend to want to replace worn parts in my own car well before I got to the FSM limit. Common sense... in a V8 with a super long chain I'd live with more stretch than an inline engine with a relatively short chain.

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1987 W201 190D

Must, try, to stop myself from saying things that will get me another infraction.

From the factory cam timing is 9*. Normal is 11*. He is at 12*. 1* out of spec is *NOT* excessive, I would bet half the members here are 12* or greater unless they have done something to correct it. Woodruff key allows for addtional 5* of correcting for a grand total of 16* before you run out of options. Now IIRC there is some discrepency in the manual and I cannot remember if its 10* at the cam or 10* at the crank (cam is 2X crank), but there is certainly room to wear.

Would I replace the key at chain at >14*? Probably. But at 12*?.............

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I do have the FSM and that is what it says...
Even if it is just 'close' to 10 degrees it means there is a good chance the other stuff which touches the chain...and causes the damage most of the time.. a rail breaking ... that sort of thing... may be a more than one chain OLD...
So replacing the chain, the sprockets and the guides and rails is really the safe and relatively cheap route to go...

I agree whole heartedly. I think it goes without saying that the rest of the parts get replaced when the chain does. Again, he is only 1* out of spec (2* at the cam).

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" Goes without saying"... sure would be nice if we could count on all the people who might have put a wrench to our old cars doing that. Probably reduce chain 'accidents' to almost unheard of.
I am still not comfortable with accepting any reading on this engine using the cam marks... the FSM specifically says not to use that method...

IIRC I tried that and the reading was some 6* off 2mm lift.

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I'm trying to understand. Please bear with me and correct me where I am wrong in my thought process below.

OK, if the factory cam timing is 9 degrees, then I have misinterpreted this entire thread. But I am still confused. In my experience (which is fairly extensive), no engine manufacturer puts a reference mark on the cam that matches anything other than 0 degrees TDC at the crank. Here we have an engine that shows 12 degrees ATDC at the crank when the cam reference marks are aligned. Now, I do understand that this is not the FSM method of checking. The FSM method uses the 2mm cam lift method. I am guessing now, and I'd like your clarification, that when the 2mm lift is attained, the crank position should be 9 degrees ATDC. What is not clear to me is that the 2mm lift position is in any way related to the reference mark on the cam and tower. I would *think* that the reference marks (which are there for assembly purposes and not precise cam timing purposes) are intended to be in alignment at 0 degrees TDC as they are on every single other engine I know of. Therefore, my interpretation (and I request confirmation or repudiation) is as follows:
1. The cam and tower marks are for reference during assembly. They should be in alignment when the crank is at 0 degrees TDC.
2. To check the cam timing, a dial indicator is placed to measure valve lift on the number one intake valve. The engine is rotated until the number one intake valve is lifted 2mm off it's seat.
3. When the intake valve is 2mm off it's seat, the crank pulley should indicate 9 degrees ATDC. Note that this is now ATDC on the intake stroke, NOT on the expansion stroke. Therefore, the reference mark on the cam should be about 184.5 degrees away from the mark on the cam tower. (Please confirm that this is a true statement!)
4. Offset keys are available to correct the cam timing as measured using this method, up to 10 crank angle degrees of offset (five camshaft degrees).
5. Once cam timing is checked and adjusted using this method, if the engine is rotated to TDC on the number one cylinder compression stroke, the cam and tower reference marks should be very close to aligned.

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1987 W201 190D

let me chime in on this topic....

Over the years, I have performed many repairs that a customer was forced to accept for fiscal reasons. I have personally seen many engines with visbily worn chains and sprockets that should have had those parts replaced, but i was asked to 'patch them up' as best I could.

In each and every case, I insisted on a new tensioner and I never saw a broken chain in one of thense engines, some of which I continued to service regularly for many 1,000's of miles thereafter.

I would recommend all new chains and sprockets in this case, but in reality, no shop I have ever worked for (including geuine MBZ facility) replaced the crank sprocket and IP timing sprocket. Most often, it was the cam sprocket and idler that were replaced.

I would not hesitate to use an offset key in this case in conjunction with a new tensioner and guides, although replacing everything would be my preference...Robert

Yes... you should try to stop yourself from getting another infraction, and I won't say something that'll get me my first.

I finally found the DIY article on this (I never knew where those DIY's were posted before, found them under the "resources" tab. I am now confident that my analysis as posted above is 100% correct, and that the OP has chain stretch close to the limit or beyond. He is not at 12 degrees by the 2mm lift method. He's probably somewhere between 16 and 26 degrees if he were to measure with the 2mm lift method. This assumes that the accuracy of lining up the cam reference marks is +/- 5 degrees.

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1987 W201 190D

You are right, I am a jack ass. It should read close to zero. I was confusing the number he got by aligning the cam with the number one should expect with 2mm lift method. Either way the 2mm lift method is the only factual representation of what the cam timing is. The notched washer is not keyed IIRC.

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