[sideshowoddity]

Alright, so my boyfriend replaced the head gasket in my baby. He took it out for a test drive, and long story short, the timing chain broke. Yes, we know, the engine may be cooked, but he was only trying to start from a stop when it gave out, so we are hoping for the best. The valves don't appear to be bent.

We have a new timing chain in hand. We have been searching high and low for information about lining up the timing marks in our M103, but have not been able to find anything. Does anyone know where to find this info? A mechanic suggested AllData.com. Does anyone have any experience with this subscription? Is it worth looking into?

Thank you ahead of time for any help you guys can offer! The people on this site are truely awesome!

 

[augapfel]

Wow, that's a major drag. IMO replacing the timing chain is quite a bit harder than swapping head gaskets. You have to pull the upper and <gasp> lower timing covers to expose the chain. You have to remove the radiator to get at the harmonic balancer, fan idler, etc. You sure you want to go there?

 

[[email protected]]

Usually it can be done by pulling the old out while feeding the new in but if its broken and you can't reach it to work it out of there, you will become very familiar with augapfel's post above. I'm betting said boyfriend may not have reset the chain tensioner before installing it. Its happened to others. If you search this site you can find online the factory service manual for the above work.

 

[sideshowoddity]

Oh, boy! We are definitely worried. One side of the chain was still exposed, so we were able to pull it out. Boyfriend is going to try to fish the new chain through there with some wire in order to try to avoid having to take the whole thing apart again (whether it will actually work, is another story.) We have been "collecting" the manuals from this site, and are having a hard time finding info on lining up the timing marks. I'm going to keep looking, but if anyone has any info on hand, it would be greatly appreciated.

Thank you so much for your responses!

 

[[email protected]]

not knowing all of the story and assuming its all out...pulling it out probably ensured you hours of work. If still in there, there was a possibility of linking the new chain to the old and while turning the engine slowly by hand feeding the new in as the old comes out (think fish wire being used to pull electrical cable in a wall). Now there is nothing to guide the chain where it needs to go. I feel for you :-(

If on the other hand, its still in there and all you did was pull up one end, there is hope!

 

[latief]

Check your PM..

good luck and post pictures :thumbsup:

 

[Real1shepherd]

OK, some thoughts on this because I did it. Attaching the old chain to the new and having a helper keep tension while the other moves the motor around in the correct direction, is the only way to go (chain tensioner removed, cam sprocket and upper timing cover removed, of course). But....these chains are unusual in the fact that they take a special MB tool to peen them back together again. Just about any chain break will remove the pin, but only a MB tool will peen the pin back properly. I have a lot of experience with equipment chains and so I peened the pins back with a miniature body tool and a ball-peen hammer. I would NOT recommend this if you are not familiar with chain links/pins, as it's far too critical on this engine at high rpm.

As far as setting your camshaft to TDC on #1, the CD shows a pic of an earlier design. I think the cutoff date was '88. Following that pic will put your timing exactly 180 degrees off for the newer design. Ask me how I know this....

If there is no chain left to connect to...so you can pull the new one through....it's not going to be done with wire etc. Off comes the lower timing cover.... You'll be lucky if there hasn't been valve damage done....

Kevin

 

[ptkacik]

I agree with Kevin. This process is called "rolling in a new timing chain" and you do it by attaching the new chain to the old one and slowly rotating the engine. Normally this is done to replace a timing chain and I've done it every 150,000 miles as a maintenance thing. When done correctly, the new chain pulls the cam around to prevent crashing the valves.

Since your timing chain broke, then the valves have probably crashed and are bent. Giant bummer. However, you might assume they aren't and see if the new timing chain will let it run. It's possible that when it broke, everything stopped so it didn't crash or maybe the lifters relieved. It's worth a try.

The other reason for rolling in a chain is to guide the new chain through all of the chain rails. As stated above, the only other way is to dimantle the front of the engine to where you can reach all of these parts. That's hard work and I've not done it on a M103 engine.

Good luck,
Peter

 

[sideshowoddity]

:shit not:You guys won't believe it, but he actually fed the new chain back on with a COAT HANGER! The boyfriend is sleeping, so I cannot ask him exactly what he did (or what the proper terminology is), but I did see part of the process.

I know that he attached one end of the chain to the top sprocket with mechanics wire so that it couldn't slip down inside, and he made a loop with the wire on the opposite end of the new chain before he dropped it down through the channel. He took a coat hanger apart, made a small hook on the end, and "fished" around until he guided it around the lower sprocket while slowly turning the engine by hand. He finally caught the loop at the end of the chain (it did take a couple hours) and pulled it back up and out the top. The chain is on, and the pin has been peened (hopefully whatever he did there will work, because we don't have the special MB tool).

I must add that he did this in the driveway, in the dark (with a flashlight in his mouth), and it was around 25 degrees out there. Call it a "hack job" but the guy really didn't want to take the whole frigging thing apart to get the chain back on there, and hey, it worked!

Tomorrow he will adjust the timing, and we'll see where it goes from there. As far as potential damage from the chain breaking, we are keeping our fingers crossed. Everything in there appears to be doing what it should when the engine is turned by hand. The chain broke when trying to excel from a complete stop. It started to go, but then stopped. There was no loud crashing sound or anything that would establish that things collided.

I think Hanno was right about the tensioner. Boyfriend was having trouble with it and didn't have the manual on hand, and now that I have looked at it, I know that we didn't realize that it needed to be reset (or that specific torques were required.) I printed it out, and I'll show him when he wakes up.

Thank you all for the input, I'll let you know how the rest goes...

 

[Real1shepherd]

Amazing what outright perseverance will do. I wouldn't have thought it possible, especially with the chain tensioner in place-that should have been the first thing to be released and I recommended that.

Assuming all is well and no valves are bent, you'll have to set the timing different than what the CD shows for '89 and newer m103's. The lineup mark on the camshaft itself is not the little bar used in the pic, but a very small dimple hole in the cam, 180 degrees opposite of the bar.

Also, I would HIGHLY recommend that before he rotates the engine around for the #1 piston in TDC, he loosen (in sequence approximating the head bolts), all the camshaft journal bolts....so that the camshaft can't move any valves. That way you can prevent any potential valve damage while turning the camshaft. When his camshaft alignment is set properly at #1 TDC, then he can re-tighten the camshaft journals to spec. He may have to pull the camshaft sprocket off a few time to find the exact chain link position, corresponding with the correct camshaft timing mark.

Kevin

 

[[email protected]]

I hate to bring this up (and I don't want to know how that saying got started), but its an old M103. Start messing with the camshaft retaining bolts and you may find one or more of their threads stripped in the head. Solution is a helicoil that can be done while the head is on, carefully.

 

[Real1shepherd]

I hate to bring this up (and I don't want to know how that saying got started), but its an old M103. Start messing with the camshaft retaining bolts and you may find one or more of their threads stripped in the head. Solution is a helicoil that can be done while the head is on, carefully.

The camshaft end journal bolts (at the front of the engine) are known to strip out with wear-not from loosening the bolts. This will be a matter to address anyway, if evident. When re-torquing, if the bolts feel 'mushy' at all, @spec, then use a thread insert. There is a better designed insert than Helicoil, but I have it bookmarked on my other PC and I don't remember the name.

Kevin

 

[samiam44]

Advice,

First on the camshaft rocker cover bolts- the factory went from 70mm to 73mm. Upgrading will greatly reduce thread stripping. You can clean the threads with a bottoming tap and then use 75mm.

It sounds like you didn't re-set the tensioner when you did the headgasket. Simply rolling a new chain in is NOT the solution. I don't think you can accurately determine if you've bent any valves without pulling the head again. Taking out the valves and checking to see if they are truely still concentric. You'd hate to have one stick open @6000 rpm.
Make sure you keep each rocker, lifter etc identified as they must go back in the same location.

Take note and re-set the chain tensioner or replace it.
Need to now inspect/replace guides with the chain failure.

If it is an earlier car Pre 91, there is an updated oil tube which should help camshaft life.

 

[orange911]

How about an update? I am hoping there is good news on the horizon.

 

[oaeyeo121003]

Crazy

I am a master mechanic, i work on these cars frequently. This summer i did two headgaskets on m103s including lower timing cover seals. Big job, there are marks to use for timing. Takes a while, lots of cleaning, good luck on that chain staying together. On resetting tensioner, push tensioner out of sleeve, re-insert into other end and torque. If you have any questions ask direct questions.

 

[mit]

I am a master mechanic, i work on these cars frequently. This summer i did two headgaskets on m103s including lower timing cover seals. Big job, there are marks to use for timing. Takes a while, lots of cleaning, good luck on that chain staying together. On resetting tensioner, push tensioner out of sleeve, re-insert into other end and torque. If you have any questions ask direct questions.

When pulling the harmonic balancer, can I just use a "normal" puller? Something like this:

Amazon.com: Harmonic Balancer Puller Set: Automotive

I haven't pulled my belt pulley yet as I am waiting for my flywheel lock to come in. I hate doing jobs for the first time!

Thanks!

Mit

 

[oaeyeo121003]

balancer

you will not need a puller, flywheel lock would be good the bolt is tight i think 220 ft lbs, mark everything where it lines up before you take it off, with paint or a center punch. i use two prybars to pop of the balancer, it is not press fit. just make sure before you put it back on that you file any marks/burs you made on it flat/ not sharp. also be sure to install tensioner properly. if not you will most like bend valves.

 

[samiam44]

The "Key" not mentioned on the balaner..

There's a key between the balancer and crankshaft. You have to make sure you replace the balancer and get it on the key. If not, you'll push the key out and it goes down into the pan. Then, balancer slips location on the crankshaft. Common way to destroy a OM617 crank.

M