380se timing chain ?
 

Today my car stalled out on the highway ,I cranked it over to restart, thinking that I had a fuel problem. The engine turned over O.K. but it failed to start ,I opened the hood to check out the engine,I noticed a hole that was punched out on the front left hand valve cover directly over timing chain & gear. The chain & gear was still intact. I called a tow truck. Tomorrow I will remove the valve cover to have a look.

Would anybody know what I will find.
P.S the engine didn,t growl,shake ,bang or screech it just stalled .


Apprehensive Rick.

As I have only seen it a few hundred times, let me guess. Upper chain rail fell apart rolling through between the chain and gear, jumping the timing, breaking the valve cover, and bending all the exhaust valves in the drivers side head.

380se wouldn't stay running
 

I figured it was probably bad news. Will confirm your diagnosis after I take the valve cover off tomorrow morning. Thanks! Rick.

Is your 380 a single or double chain ? if you plan to keep the car and it's a single row sure would be the time to convert it to a double row chain if the rest of the engine is in good shape.Doing a change over is fairly labor intensive and all sprokets have to be replaced,if your 380 engine is tired might be smarter to put in a used engine seeing as how you are going to need both chain and head work. I really like the 420 engine that is in my 500 SE a 420 engine should fit right in and would give you a nice power increase you might need a 420 ECU ........
William Rogers.....

380se is a double chain
 

william: my 380se is a double chain (1985), but thanks for your response, I appreciate your taking the time. Rick.

.....and I've noticed from reading the hundred or so posts on this issue that this problem is not usually caused by a loose or stretched timing chain jumping a tooth on the cam sprocket, but rather by an upper chain rail guide breaking (by being slapped by the chain) and the plastic bits and pieces getting lodged in the chain and then getting jammed as that part of the chain hits the cam sprocket.

The chain rail guides are made of plastic and get hard and brittle over time and are easily broken.

Rick-

Just curious, at what mileage did this occur? I feel your pain. My 450SLC broke the driver's side upper rail. I was a little luckier, limped in to mechanic before bending valves (jumped only one tooth?).

I wonder if a stretched/loose chain slaps around more especially when there is less oil pressure at the tensioner, and a chain slapping a brittle plastic guide exacerbates the problem.

Dang this design! What's the point of using a chain as opposed to a belt if it has these weak plastic guides?

Best of luck.

Boy I agree with that! look up the price of a new factory crate engine I bought a house once for less than the cost of a new engine for my 500SE.Seems like with those prices and the space age materials we got now there would be some better material to make both the chain and guides from , after all Mercedes was a leading maker of airplane engines I wonder how many plastic parts they used in them.........
William Rogers........

The more the chain is worn, the longer it is, so the more "slop" there is taken up by the tensioner.

When the tensioner bleeds down (as it does when the engine is off), the chain slaps around until you get oil pressure -- needless to say, the more slop, the more slap, and sooner or later the guide gets cracked or broken. There goes the chain, unless you are REALLY lucky.

Check the chain stretch often, it's far cheaper that doing valves.

Peter

Don't worry about the chain, replace the rails as soon as they start turning color: atleast every 3-5 years. The double chains will last easily a couple hundred k.

The chain on this motor will still be intact (but obviously should be replaced).

I appreciate all the responses I got to my question. Someone asked the mileage on my engine. It's 160,000 miles, more or less. Steve was bang-on on his diagnosis. This is what I found when I started taking her apart: definitely the rail let go. All the rocker arms on the exhaust, I can pluck them out with my fingers when the cam is on its low side, so definitely the valves are bent. Next weekend I'm going to pull the left head off and check for piston damage and at the same time I might as well pull the other head since I'll have the intake off anyway. If it isn't any worse than the bent valves then I'll proceed with the repair. In your experience, is there anything else that I should be checking for? Rick.

There is never any piston damage.

Never is a big word and in all the ones I have done there was no damage. I have heard of valves breaking and the pieces embedding in the pistons. If the heads are still on the valves just do a valve job and replace the guides with OE MB and you will have done justifiable maintenance anyway.

At that mileage the front lower right rail (removal requires front cover removal) will be OK (for another 250K). Replace all the head rails and the tentioning rail and have a new motor.

This may be of interest.

http://www.import-car.com/ic/ic40024.htm

Also check out www.pindelski.com

Select Cars, Technical, then Motors. He shows chan rail and timing chain procedures on his M116 and M117 engines.

He posts here under Thomaspin.

Thanks guys for the pictorials. Rick