I am in the middle of replacing the timing chain (84' 300TD), valve cover is off and I just measured the chain stretch to be 11 degrees by using the TDC mark on the cam and checking the degree mark at the crankshaft. I inspected the tensioning rail (banana shaped one, Type B hook) and found it to be out of alignment. This is evident in two ways: the chain tensioner shaft is out of alignment with the tension rail shaft by about 1/8" (see pictures), and the tension rail pad is about 3/16" off center with the center of the chain angled towards the back of the engine (have a picture of this too but can't load 2 pics on this post).

I have a few questions that I was hoping to get some help on:

1. Why is the tension rail out of alignment?

2. Does the tension rail need to be replaced? If so, does this rail just slide off a pin once the chain tensioner is removed?

3. After I replace the timing chain --> Is it sufficient to simply reassemble the rail and tensioner and assume the tension rail will stay in alignment?

Please let me know.

Thanks!
Billy

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If you don't have a manual, I suggest you get one. Haynes is cheap and covers pulling the pins which you are going to need to do. Its not a bad job but you definitely need at least a Haynes. Good Luck

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I have seen this before and have not noticed any adverse effects from it. If I remember correctly, I replaced the tensioner in the first engine in the 300D that was like this. The new tensioner lined up the same way. About the only way, in my opinion, there is to line it up is to shim the lower end of the rail closest to the block. Not exactly sure how you would get the shims in there though. You can drive the car a long time like this.

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Jim

Thanks for the input Engatwork! You saved me what could have been a massive endeavor. I put the timing chain in and replaced the chain tensioner. The old chain tensioner ratchet mechanism was stuck in place and no longer worked. The noise the car was making previously (loud unbalanced chain noise that mimicked a wheel bearing at higher enginer RPM's) is now gone and the engine runs smooth. Thanks again for the help! I don't know what I would have done...

Cheers,
Billy

Interesting topic and excellent picture.

Engatwork - wouldn't the piston align progressively better with the pin as the chain stretches? The piston extends further, as the rail pivots around, dropping the relative position of the 'anvil' on the rail.

Thomas I did not see that happen. I did see it eventually wear a little "half moon" shape into the guide rail pin after which time I replaced it.

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Jim