300D Timing Chain replacement
 

Ok.. Thanks to Eskimo and the loan of a dial gage I now know that my chain is either stretched or I've got a busted key.

Knowing what the eyeball marks look like I checked that way first. 10 degrees.

Setup the dial gage, twice. (First time I checked the #1 exhaust valve.. doh!).

With the dial gage.. assuming I did it correctly I read around 20 degrees. I didn't make note of the cam ID so I'm not sure what that would translate to. But I figure its around 10 degrees or so.

Looks like new chain time. I wanted to also do a compression test. But I assume that with the timing so far off it would be a waste of time to do one.

On the subject of woodruff keys.. Would a new chain come with a non-offset key or would I need to buy one of those?

JamesStein,

Off the subject, but I noticed you are using WVO in your cars. Do you process your own or buy it from a producer? I have some interest in biodiesel and wondering what you think about it.

Marks88

James,
It is a fairly simple proposition to remove the gear from the cam to check for a sheared key. Release tension on the timing chain by removing the tensioner. This will give you an opportunity to check the condition of the tensioner and the spring inside. The upper chain guide is held on with one bolt and a pin that must be pulled. A bolt of the correct thread with a stack of washers, sockets, spacers, etc. does the job nicely. Once the guide is off and the tensioner removed tap gently on the back of the cam gear towards the front of the car. It should slide forward with little effort. Keep tension on the timing chain with a bungee cord from above or a piece of wire slid though the links from underneath. I don't think a new chain would come with a new cam gear key but ordering one should be no problem. BTW, thanks for the taillight sockets! Got them installed. I would like to send you at least the postage fee but I cannot read the Street # in your address. Please provide. Thanks, RT

I was trying to avoid pulling the cam gear off first. However, I suppose its worth a look. I just don't want to make my life even more difficult by letting the chain slip. Is there also a key on the balancer as well?

Haha, my plan to confound your attempts to pay me for the sockets has worked!

In all seriousness though. I was able to borrow a dial gage and a compression tester from eskimo gratas. So have a Merry Christmas and enjoy your brighter taillights. I'll consider it a payment on my MB Shop karma.

James,
Thank you very much! I guess I have no choice but to accept your generosity. Regarding the cam gear, its quite simple to remove and since you have to release the tensioner to roll in a new chain anyway its just one more step. Take a good look at the tensioner spring. Mine was half worn through and likely would have broken in the near future. A new spring is cheap insurance. I wouldn't worry about the crankshaft key. If that had sheared I don't think the engine would run at all. Word of warning. When you torque the cam gear use a metal rod (long 3/8" extension) through the cam gear to keep it from rotating. If you don't do this you will put all the pressure on the tensioning rail and tensioner. Good luck, RT

How many miles are on it James. In my opinion, rolling in a chain is about as easy a thing to do as it gets. Personally, I would just go ahead and put a new chain in and take another measurement. Chances are you will be fine. I'll be surprised if you have an offset key in there but I would not worry about that till after I installed the new chain The cam sprocket is pretty easy to remove. Just make sure you mark the cam sprocket and chain where it goes back to the same spot.

A new chain will not come with any kind of key.

220k'ish. The odo was flaky when I bought it. From day one its had power issues, but they have been steadily getting worse.