300SD Broken Timing Chain Repair - PeachParts Mercedes-Benz Forum

mplafleur · #1 12-06-2004, 10:14 PM

It's time to get my 300SD engine back together. Some may remember I bought it on eBay a month ago with a broken timing chain. Can't see any valve damage, but it doesn't matter as the cam is broken in three pieces as well as two cam towers.

I've taken the head off and got a replacement from a friend (Thanks 300SD Sady!). I pulled the pin and put in a new chain slide rail. The replacement head is ready to put on. But first I want to install a block heater as this block does not have one. I purchased a 19mm allen key and used a 5 foot pipe to loosen the plug. A 1-13/16" socket and a 3/4" ratchet helped me get the heating element into the block. I replaced some of the coolant and verified that the element worked.

It was misting outside so I closed the hood for the night. Now for some deep thoughts and planning.

The chain is hanging out the driver side of the block and there is none on the other side of course. This means I can't roll in a new chain (even if it were timed correctly).

My thoughts were to remove the oil pan and either thread a wire or chain down the banana rail and connect it to the end of the broken chain at the bottom of the pan by the crank gear. I could then turn the crank and bring out the new chain. I could alway loosen the chain and turn the crank until it get to TDC so that I could set then the cam timing.

Good? Well not quite as the IP is not timed at all!

I guess I'll have to take off the IP, but how do I time the gear for the IP?

psfred · #2 12-06-2004, 10:41 PM

I'd pull the balancer and the vac pump. Drop the chain down the driver's side and fish around the timer and down and around the crank (chain is accessable on the 617 with the balancer pulled) and then use some wire to pull it up while turning the engine backwards. You could do this the other way if you want, I suppose. Should be fairly easy with the head off.

Crimp the chain and then hold it up while setting the crank to TDC on #1, then install head and cam, get the cam timing correct, then pull IP and set it correctly and adjust timing.

If you want to pull the engine, you can just turn it upside down and drop the chain in after you pull the lower pan. You will still have to fish it around the injection timer (remove the "lock" screw on the side) and crimp on the sprocket.

Whatever you do, I suspect you will have to pull the IP to set it.

Peter

mplafleur · #3 12-06-2004, 10:53 PM

I didn't really want to pull the balancer and the vaucuum pump. (are you saying to take off the timing chain cover?)

Is the injection pump timing gear marked? Or does it not matter where that gear is?

If not, could I remove the IP, get the chain threaded through somehow timed with the cam and then put on and time the IP?

Does removal of the vacuum pump give me front access to the IP gear?

psfred · #4 12-06-2004, 11:25 PM

New to 617s, eh?

Timing chain "cover" is part of the block casting, non removable (to say the least....).

You will have to remove either the oil pan (lower part) or the balancer to get the chain around the sproket. If you want to leave the engine in place, I'd vote for the balancer just because you are right there, and it's not TOO bad. Look up Larry Bible's hints on re-installation.

IP will HAVE to come out to time it, there are not external marks. When you pull it, you will find a missing spline, an index on the crankshaft (of the IP) and a mark on the face -- set engine to 26 degrees BTDC, align marks on pump, and re-install. The IP drive spline goes into a sleeve that fits on the matching spline on the injection timer (behind the vac pump). You will then need to actually set exact IP timing by the drip method (again, a search should get good instructions).

Take a good look down around the crank with the tensioner rail out. If you can see even a link or two of chain, try to snag it with something and pull it up while you run the crank around backwards to get it up far enough to grab. You can then use the old chain to pull a new one in.

Peter

mplafleur · #5 12-06-2004, 11:45 PM

Thanks Peter.

While I'm not exactly "new" to to the 617, it has been 15 or more years since I've had one apart and I do think that my oldest brother put this part together while I was at work.

OK, I take the IP out and reset it. I have a digital tester to set the timing.

BTW, I fished out one the clips for the timing chain. From what I can tell, the timing chain broke at the master link which was not a crimp style.

mplafleur · #6 12-22-2004, 09:36 PM

Here's an update.

I removed the injection pump last night and then the vacuum pump. When I took the vacuum pump off, some pieces fell out. I didn't think that was right. Look below to see what I found.

The bearing is seperated from the arm and the shaft through the spring is bent. The insides of the pump seperated and got stuck in the gear. This is why the timing chain broke. Interestingly, the chain broke at the connecting link, which was a CLIP and not the crimp type.