Timing chain rails

[travellerdogs]

I'm back with a new subject. On checking my timing chain and top guide rail it looks like it's time for a new chain. Had lots of slack on chain but I levered the tensioner sprocket against the chain as far as it would go. There's still a bit of slack on the chain on the down side as it slides over the guide rail. The guide rail has deep grooves in it from wear so it's time for new chain and rail. Question. I can get at the top rail on the but where are the other two rails and can I get at them without dismantling the head and the front of the engine. I would like to just change the top rail. On my 380 Sl it is usually just the top left and right rails and the tensioner rail that really wear the most. I just checked the mileage on my car and it shows 11862 which indicates it has over the hundred thousand mile mark.  I also read here that the tensioner rarely ever screws up as it is strickly a mechanical device which fills up with oil from the pocket. I've done them on later SL's but they are different in their construction and they do get bad. Thanks, Carey

[ja17]

Hello Carey,

The chain may come to rest with a bit of slack on the downward side. Back the cam sprocket up just enough to take up the slack, then check to see if the tensioner takes up the slack on the passenger side. If it remains loose, your chain is most likely ready for replacement. Now if you depress the tensioner and you can move the chain over the teeth on the cam sprocket, you definately need a new chain. With a new chain, you cannot move the chain over the teeth even with the tensioner depressed. Chains should be replaced as standard preventative maintenance on these engines every 100,000 miles.

Lower chain rail replacement on these engines is difficult unless the engine is dis-assembled.  They are not normally replaced with the chain, unless they have been damaged or the engine is apart.

Early MB engines had aluminum/rubber rails. That do not break and fall into the chain gears like the plastic ones on the later V-8 engines. Unfortunately the newer replacement rails are plastic. Hopefully they have improved the materials. Heat, age and chemicals takes it toll on plastic in engines.

[travellerdogs]

Hell Joe. I'm ordering up a new chain and top rail. There is deep grooves worn in the top rail. The chain has a lot of sideways slack before I levered the tensioner sprocket over against it. With the chain tensioner sprocket pushed over against the chain there is a bit of down slack There is no tension on the tensioner, haven't had the car running enough probably to pump any oil up. When I sprayed a bit of fuel in the intake, it only fired up for a second, just enough to blow some mouse seeds out of the muffler. I'm going to order a new tensioner as well, I want to change a small hose on the thermostat housing anyways so just for safety I will change the tensioner and thermostat as well. When I took the IP off I picked two tiny pieces of plastic chain rail up just where the coupling meets the IP gear. Thanks for the help. Carey

[w113dude]

Carey,

Take a look at the top sprocket on the cam this also may need changing, I recently changed one & made a big difference.