Sadness... Broken Timing Chain on '81
 

My timing chain on my 1981 300TD with ~330k miles on it broke last week. This was the original factory chain. Car otherwise ran great. No oil consumption, no loss of oil in the incident.

I was accelerating lazily from a stop light when I felt a shaking in my right foot through the accelerator pedal and heard a clanking scraping noise and then the engine died.

The cam broke and it took out a couple towers.

My mechanic is recommending a motor transplant because it would cost about as much to get in and replace the cam and towers and chain. He's concerned that the teeth on the gears might be worn and that a replacement chain could be damaged and cause another failure.

Thoughts?

I'm thinking that my 6-year stint as a 123er is coming to a close. This car is in really nice shape. I'm amazed at the paint and chrome on these fabulous cars.

Part it out? Sell it as a project?

really tough call that only you can make based on the condition of the rest of the car. If it is great, you can always find a donor car to get an engine out of whose body is crap etc.

in AZ, I am certain the vehicle is flawless... maybe interior fade, cracking etc...
I agree with your mechanic, put a replacement engine in there... save the head from your car, heck, go get a motor from any 82-85 diesel, and have your mechanic rebuild your head with new valves, and parts from the donor motor, and be ahead of the game with better compression up top!

if you decide to sell the car, many members here would snatch it up. ebay the thing with the blown motor for a rust belt MB'er looking for a great chassis.

Good advice from all of you... It's nice to hear from folks who appreciate these machines. It has amazed me ever time I work on it. And you're right, it has lived an easy rust (almost) free life. 1981-2006 in Socal and 2006 on right here in dry, sunny auto preservation land. I think MB Tek fabric is one of the most amazing fabrics ever used.

what caused the chain to snap again? describe what happened for the benefit of the less informed (like me!)

Absolutely NO idea. Oil was fine. Mileage had increased in the past few months from 22.5mpg to 24.5 mpg. I was very good about changing the oil regularly. Did the valves once per year (I now know I should have been inspecting the chain). Vacuum was a bit low at 15mm, but working, so I don't think the vacuum pump was the cause. We just did a 800 mile trip to Colorado for skiing over Christmas. It ran like a champ on the trip. Maybe it was just time...

the vacuum pump can cause a motor to fail? how?

the vacuum pump is driven by the chain, it's opposite from the IP, and it's got bearings, and steel parts that can fall into the chain and cause timing to skip, resulting in valve contact with pistons, or debris can get in the chain, and jam a gear, or cause the chain to rise and bind in the block or valve cover... messy...

On some cars the bearing in the vacuum pump can fall apart and drop hardened steel ball bearings into the timing chain gallery. They can get caught in the chain and cause problems immediately, or sit in the oil sump until they wear through the pickup screen and get pulled into the oil pump, jamming it.

is this for the 61x and 60x engines?

yup

If you love the car don't let it go.

I don't want to. I have a love of old vehicles. 4 1960s motorscooters, a '74 step van, and a '97 BMW E38 share the garage with this one.

Answer
 

FYI: The 1981 300TD has an OM617

This is why I replace the timing chain around 200K.

To answer your question, if you are lucky:
* Pull the head.
* Replace the camshaft and towers.
* Replace valve guides and valves as required.
* Replace the timing chain and rails.
* Reassemble.

A replacement engine is another option.

.

Hopefully you will be lucky, but do check the shaft that drives the ip, this was bent on one that I worked on that broke a chain. Chain broke from vacuum pump dropping in parts.

Man, that's sad indeed :(

I keep telling my friends with gassers to replace the timing chain every 125-130 miles.I do it regularly on all my cars and I've never had one break. My ex mechanic on the other hand had a beautiful S500 (w140) with 135,000 on it. I told him to change the chain and he laughed. Four days later I got a call asking if I could drive him home because his timing chain broke!:eek:

I tried not to laugh.....it was hard though:D

If you really love the rest of the car, I'd find a donor engine, make sure it has a good compression and cylinder-leak-down (and coolant leak-down) test results, and then drop it in.

Sincerely,

PE

I just posted the following on the other thread you posted on, reading through this one, seems like you are going to jump in and keep her. and this not being your only set of wheels, this will give you something to do in your spare time. ;)


Sorry to hear about your engine loss, know that sinking feeling especially when you are out in the middle of no where cruising along at 65mph.
every valve hit a piston, broke the two front cam towers, one off at the base and the other just under the bearing. cracked the valve cover, twisted the rearmost rocker and cracked the head.

If the body is in good shape, why not locate a used engine, maybe up grade to a Turbo 617.952. I see them in PNP from time to time, and not all are junk. pulled one with 97K.
some time I have seen them on Craigs List.

If you are done with the car and it`s in good shape, shame to part it out. the inventory on these is thinning down on good one`s.
really not all that difficult to R&R an engine.


Charlie