603 Timing chain Stretch Report, what maintenance really means...

[87tdwagen]

Hello All,

Before hotrodding (IC and modified IP) my 87 300TD and after reading all of the horror stories regarding timing chain failures etc I figures I better check mine out first.

My car luckily came with all the docs and history, I mean, I have never seen such a complete history report, brouchures, window sticker, dealer maintenance reports from mile 5 to 200k. Anyhow, nowhere does it state the timing chain has been replaced, matter of fact, outside of AC troubles and oil changes, nothing else was reported in the history. The orginal owner also does not recall changing the TC.

This 603 still has the #14, so I guess routine maintenance is Key to limiting chain wear. I followed the chain stretch measuring procedures, lined up the cam marks and checked the crank marks 5 times around, each time coming up with 0 deg. of difference...well once it showed 0.5 deg, but I think I was slightly off at the cam, not the best marking method used by MB IMHO.

Anyhow, is this usual? unusual? my baby has 215k mi and so far from eyeballing it 0 timing chain wear? Any comments

The engine internals from what I could see were very clean, and the cam lobes looked really nice, very clean, obviously well cared for.

[sixto]

Originally Posted by 87tdwagen

... after reading all of the horror stories regarding timing chain failures...

Can you elaborate? I've read just about every 603 post on this forum and a couple others and I've yet to read of a 603 that coughed up a chain... other than because the vacuum pump disintegrated.

70s and 80s V8s will wear chains especially single row 116s. Some 602s had sprocket and chain problems. Maybe a 617 or two but I'm sure that's because of poor maintenance and the sheer number of them getting up in miles.

Sixto
95 S420
87 300SDL

[87tdwagen]

Well not to say that the 603 is bad or anything, but there are several reports of know problems with these timing chains, what those problems are I don't exactly know, nor how much may be wrongly attributed to the chain and not other things such as tensioners, guides etc.

But in researching I noticed that everyone who has replced a 603 chain, recommends at 200k mile intervals and some have noticed 3-4 deg of stretch in that time, which is what MB calls, time to replace. I just can't figure if it is or can be "normal" to have zero eyeball wear after 215K mi??

[sixto]

We might be mixing who "MB" is. I haven't seen anything in the service or maintenance manuals that says to change the chain at 200K miles. I haven't seen anything that says to align cam marks and read off the crank pulley as a means to determine chain stretch. Lots of sage advise from experienced techs and DIYers have been taken to be gospel... and with good reason.

The proper way to measure chain stretch is in the manual. It calls for instruments most people don't have. Eyeballing by an experienced eye is probably a reasonable shortcut. Taking 5 readings is an excellent way to eliminate variables. How about getting another pair of eyes to agree that the timing marks are aligned? Just to eliminate an area of subjectivity.

To your point, it's exactly the case that proper maintenance will keep these engines in top shape for a good long time.

Sixto
95 S420
87 300SDL

[87tdwagen]

[QUOTE=sixto]We might be mixing who "MB" is. I haven't seen anything in the service or maintenance manuals that says to change the chain at 200K miles. I haven't seen anything that says to align cam marks and read off the crank pulley as a means to determine chain stretch. Lots of sage advise from experienced techs and DIYers have been taken to be gospel... and with good reason.

The proper way to measure chain stretch is in the manual. It calls for instruments most people don't have. Eyeballing by an experienced eye is probably a reasonable shortcut. Taking 5 readings is an excellent way to eliminate variables. How about getting another pair of eyes to agree that the timing marks are aligned? Just to eliminate an area of subjectivity.

Sixto, I'm sorry I wasn't clear, most people on this forum seem to indicate that 200K miles would be a good change interval for the chain. Not all agree, nor do I on this point, it's just repeated by many others.

MB I bellieve calls for changing the chain on the 603 when it is more than 4 deg stretched. This is the advise I'm most likely to follow.

As you mentioned, I do not have all the MB tools needed to measure this with precision, and most indy's as well as dealers in the area are driven by cha..ching. so I took the advise of many other list members on the eyeball check to see whether further investigation is needed.

What I did was turn the engine via the harmonic ballancer with the cylinder head cover off, until the notch on the cam hub (closest to the sproket) lined up with a protruding line cast into the #1 cam bearing cap, 12 O'clock position. When I did this, the timing marks on the harmonic ballancer lined up at 0 deg or the hask mark between the 0 and T.

I agree that a second set of eye's will help, but since arrrg I've gots me only eye...I repeated again another three times with the same results.

Am I doing this wrong? Please let me know how I can recheck the results or test differntly with commonly available tools.

Thanks,
Bill

[rdanz]

If I remember correctly there was a service bullitin regarding premature stretching of timing chains in 603's -reason being a batch of defective chains