Camshaft broke - 603.970 - PeachParts Mercedes-Benz Forum

krwsenior · #1 02-08-2015, 09:03 PM

75 mph on the interstate with cruise set. Felt a slight "thump" then the rpm's fell and no accelerator. Bumped the tranny into neutral, and coasted to a safe place on the other side of an entrance ramp (thankfully close). Opened the hood to see this....

Towed home and started taking it apart a few days later.

I rolled a new chain in and replaced the tensioner a few months ago, maybe 5000 miles. I suspect that a piece of "something" broke and got into the chain/sprocket putting pressure on the cam and gear, which broke. Thankfully there wasn't any internal damage on the front of the engine. Only one valve made contact with a piston.

krwsenior · #2 02-08-2015, 09:10 PM

The head is in the shop. Need all 6 exhaust guides, 2 intake valves and 3 exhaust valves (and seals). Going to resurface also, ordered shims for prechambers (and also spline tool).

The cylinders looked exceptionally good, except for number 3, which is the same one that the valve came in contact with. No marks on piston skirt.

Pulled the pistons and honed all 6 cylinders. Was able to bring it back. No wear lip at top of cylinders, just carbon build up.

krwsenior · #3 02-08-2015, 09:22 PM

Checked piston height - slightly out of spec on a couple of them, but I'm not going to attempt straightening the rods. Going back with it as is.

I used as many original MB parts as I could find or afford. I'm glad I replace the rings, since number 6 had a stuck compression ring and a lot of carbon build up. A year or so ago I cleaned the intake manifold and found the number 6 and number 1 tubes were almost completely clogged.

Pistons look good. Rod bearings look good too, but replacing anyway. Had to have some welding done on the pan and cam cover. The pan had a weeping leak from damage done years ago. Welded it on both sides to beef it up.

krwsenior · #4 02-08-2015, 09:27 PM

The new chain that I had just installed had scars on the inside middle from the event - so another new IWIS chain and went ahead and changed the oil pump chain too. As well as the crankshaft gear (SWAG, couldn't find MB)

EJHumber · #5 02-09-2015, 12:23 AM

looks like its coming along. are you doing all this with the engine still in the car?

vstech · #6 02-09-2015, 12:39 AM

Vacuum pump?

biopete · #7 02-09-2015, 01:10 AM

Wow. Nice work. Are those injector line heaters? It had to be the WVO. That kills engines you know

ROLLGUY · #8 02-09-2015, 01:45 AM

Quote:

Originally Posted by vstech

Vacuum pump?

That was my first thought as well. Had it happen on a 617. It was definitely the vac pump that caused it:

Stretch · #9 02-09-2015, 04:12 AM

Quote:

Originally Posted by vstech

Vacuum pump?

I don't think so. That looks just like the mistake I made on my M102. I incorrectly set the timing chain tensioner and the end of the camshaft snapped off just like that. Luckily for me it happened at idle. On a petrol engine I could hear a weird whining (that I now know what it means!) that I guess might have been masked by the glorious sound of a diesel.

krwsenior · #10 02-09-2015, 07:15 AM

Quote:

Originally Posted by EJHumber

looks like its coming along. are you doing all this with the engine still in the car?

Yes, I left the engine in the car. I didn't expect to do anything but head work when I began.

krwsenior · #11 02-09-2015, 07:17 AM

Quote:

Originally Posted by vstech

Vacuum pump?

No, it wasn't caused by the vacuum pump. When I rolled in the new chain, I replaced the original VP with a used one which had the upgraded bearing. I'm still not comfortable not knowing what caused it.

krwsenior · #12 02-09-2015, 07:19 AM

Quote:

Originally Posted by Stretch

I don't think so. That looks just like the mistake I made on my M102. I incorrectly set the timing chain tensioner and the end of the camshaft snapped off just like that. Luckily for me it happened at idle. On a petrol engine I could hear a weird whining (that I now know what it means!) that I guess might have been masked by the glorious sound of a diesel.

Hmmm. Not sure about this. I replaced the tensioner and made sure to prime it. The car ran great, and didn't make any noises that I could hear.

krwsenior · #13 02-09-2015, 07:21 AM

Quote:

Originally Posted by biopete

Wow. Nice work. Are those injector line heaters? It had to be the WVO. That kills engines you know

Yes, I have a single tank kit that I use in the summer only, and usually lightly blended even then. I have a switch on the line heater so I can turn it off when not running canola oil.

krwsenior · #14 02-09-2015, 07:33 AM

Here is a pic of the upgraded VP I installed a few months ago.

And The Colonel's current status and location

Hopefully I'll have him back together in a couple more weeks. Parts and machine work are taking a while.

Stretch · #15 02-09-2015, 08:22 AM

Quote:

Originally Posted by krwsenior

Hmmm. Not sure about this. I replaced the tensioner and made sure to prime it. The car ran great, and didn't make any noises that I could hear.

At the risk of appearing to be stubborn (!) there is mention in the FSM about tensioner trouble - including the formation of burrs - and over pressure disks =>

http://www.startekinfo.com/StarTek/outside/12264/Program/Engine/602_603/05-310.pdf

{Interesting to note that this tensioner does not have the bayonet mechanism that has to be re-set on my M102 but that it is an oil filled system much like the non turbo OM617}