8* chain stretch OM616

[zeke]

I am still trying to find my missing mpg on my 1980 240D.

I measured chain stretch using the cam tower hash mark method and the indicator was at about 8*.

Should I correct this much stretch with a woodruff key or buy a new timing chain?

I will take pictures and post them over the weekend. I am going to do the dial gage indicator method to compare the 2 results.

In the meantime, I am interested in thoughts on this......

[Stevo]

I wouldn't fool around with a woodruff key, just roll in a new chain if in fact your stretch is 8 degrees.

[barry123400]

Sounds like it's new chain time. Should help in many ways. Go over to Cervans rack damper pin thread and have a look. Part of the thread has to deal with low fuel milage as well. Especially on 240ds. One of my own interests actualy.

I could never get past the 5-6 miles milage difference between otherwise identical good running simular examples of them. The cause of it seemed very ellusive. Perhaps at last not now.

[zeke]

I am weighing the options of DIY versus indy.....

I can certainly save some money by buying my own parts and DIY, but the cost of the chain press might make up for those savings (as well as my time and tears).

How many hours would a specialized shop require to do this job?

[Scott98]

According to the factory service manuals, it is allowable to use a woodruff key up until the point you can no longer eliminate the stretch with one. Having said that, there is certainly no harm in installing a new chain. You can get a woodruff key for around $10, a chain is around $120. FWIW, I put a woodruff key in mine.

Scott

[jt20]

Originally Posted by Stevo

I wouldn't fool around with a woodruff key, just roll in a new chain if in fact your stretch is 8 degrees.

I amk w/ stevo.

reduce the error instead of adding error to a very critical part of your drivetrain.

"if in fact, your stretch IS 8*"

Throw in a 4* offset key and set the injection timing.

[Scott98]

Originally Posted by forcedinduction

throw in a 4* offset key and set the injection timing.

+1

[jt20]

Originally Posted by ForcedInduction

Throw in a 4* offset key and set the injection timing.

Understanding the ease of this task is reasonable. It makes alot of sense and is a factory approved method.

The other side is the one that errs on the side of caution. If this is a car you pamper, you will not want to ruin the cam sprocket and crankshaft timing gears by wearing them down with an elongated chain.
These gears were made to be replaced w/o removng the engine ,But i would never wish that upon anyone. By practicing (overly) preventive maintenance, you save yourself some effort in other ways.

[Diesel911]

Originally Posted by jt20

Understanding the ease of this task is reasonable. It makes alot of sense and is a factory approved method.

The other side is the one that errs on the side of caution. If this is a car you pamper, you will not want to ruin the cam sprocket and crankshaft timing gears by wearing them down with an elongated chain.
These gears were made to be replaced w/o removng the engine ,But i would never wish that upon anyone. By practicing (overly) preventive maintenance, you save yourself some effort in other ways.

Don't for get the timing chain guide rails too.
I have read a lot on the Forum concerning replacing the Chain and the Chain Tensioner but not about all of the other parts that also wear as until now no one has made much comment on them. I say good call.

I would think that the Crankshaft Drive Gear would have the most wear of all the gears on it as it has less teeth to spread the load over and has the full load of pulling everthing else.
Also, if a timing chain has 8 degrees of stretch and your Oil Pump is chain driven it could be a good idea to ceck that also and the Oil Pump Chain Tensioner.

Changing the chain is a waste of time if you don't change the rails as well.

[zeke]

Well, it seems like if I go with a new chain, I am looking at a chain, tensioner, rails, press (maybe I can borrow one), and possibly new oil chain and oil chain tensioner (have no idea about THAT job!)

Seems like I am up in the $500-$1k range DIY, so I shudder at how much an indy would charge.

I will measure with the other method this weekend and think about my options and report back

Thanks for all your comments so far!

[jt20]

the 240d only has the timing chain, the oil pump is much different. your tensioner should be fine, but replace the spring inside no matter what. The most important guide rail to replace is the banana rail on the tensioner.
If your life depended on it, you could roll in a chain w/o new rails, they will not effect timing, but tensioning could be poor due to a worn banana rail.

when removing any of the slide pins.. start them in another manner other than the slide hammer. it will save you aggravation and broken pieces if they are original.

[Stevo]

Originally Posted by zeke

Well, it seems like if I go with a new chain, I am looking at a chain, tensioner, rails, press (maybe I can borrow one), and possibly new oil chain and oil chain tensioner (have no idea about THAT job!)

Seems like I am up in the $500-$1k range DIY, so I shudder at how much an indy would charge.

I will measure with the other method this weekend and think about my options and report back

Thanks for all your comments so far!

No oil pump chain to worry about but it wouldn't hurt to pull the pump and check the bushings inside for ware.

[barry123400]

Besides the stretch of 8 degrees. You probably have no proof the chain is not the original one. I noticed your overall indicated milage reading.

Even if it is accurate the chain might have been in service almost too long already. May be dangerous to exceed 300k on the original chain. Thinking fatigue. The gentleman that pointed out sprocket wear is correct as well. The other problem i feel occurs. As wear progresses it actually increases at a faster rate. This may be subject to some consideration . Some people do not believe that but I personally do.