Recently I had some severe engine problems and had to tow my 82 240d home. The issue was a loud noise (thackthackthack) and a loss of power. When I took it home, for safe measure I replaced vacuum lines. The engine sat in idle fine but when I tried to pull it out it started making the engine noise after a minute of driving low rpm, so I cut the engine and pushed it home. Now it won't start again (although the starter works and has been replaced recently).

Tonight I opened the valve cover and attempted to check to seek if the tdc notches lined up, make sure the timing belt wasn't out of place, and check to cam for cracks. There are no superficial signs of stress, however I could not check the notches or the timing because I'm not able to turn the engine from the power steering pump bolt (the belt slips without turning anything but is not obviously loose). I think I may have an engine lock up. Anyone advice from you experts would be immensely appreciated in my time of Benz crisis.

Specs: 1982 Benz 240d with an auto tranny.

I wouldn't assume the engine is locked up because the belt slips. That's common. Remove the glow plugs and it should turn over easily. What is your oil pressure like?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Ah, this will prove very helpful in the morning when I tackle it again; i'll update with results. Any advice on how to go about checking for bent pistons, broken/"jumped" chain? Or is it fairly straightforward?

I saw a very thorough outline on aligning notches (TDC), but I neglected to save and can't seem to find it.

I think checking for bent pistons or jumped chain is a little premature. Can you give more details on the exact sequence of events that lead up to the engine noise? Did it have oil pressure when it was making the noise? Did you check the oil when it started making the noise? Was it full? Where on the engine is the noise coming from/ Front? Back? High? Low? Can you post a video of the engine making the noise?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

also, I'd use a 27mm socket, and extension on a 1/2" drive ratchet on the crank pulley center bolt to turn the motor over...

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That is definitely an interesting approach when it comes to resolving "severe engine problems."

Which vacuum lines did you replace?

And, just in case, I would tie the stop lever down while doing that...

i think the chances of cold compression starting a 616 or 617 *by hand* (i think it would be impossible) don't warrant tying the lever down.

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I agree. Turning it by hand will never start the engine. You can't rotate it nearly fast enough to get it to fire. You can't even get it fast enough to inject fuel.

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The events that led up to the noise were unremarkable. The noise started after a minute or so of driving on the highway. I pulled over immediately and--not seeing any smoke--checked the oil. It was well below minimum so I went and picked some up. I restarted it and drove another minute or so and the noise began again, so I killed the engine and towed it home. During the drive, the engine was not overheated and oil pressure sat at 3/4.

The car sat in idle fine (no noise) when I got home. I pulled it out for a short drive and the noise began again and I immediately stopped the car and pushed it home. Now the car doesn't start (the starter works so I'm assuming no vacuum-->no compression, hence changing the vacuum line). I've also replaced the fuel with no luck. So now I'm unable to get a vid of the noise since the engine won't turn over. However it very much sounds like this 240D Engine Noise: Piston Slap 2 - YouTube.

So what I plan to do now (and any advice would be immensely appreciated and paid forward):

1) Take off the lower oil pan and check the pistons for broken skirts.
2) Remove glow plugs and turn engine
3) Lift cam to check for broken cam (I'm not sure how to go about this). & double check chain.
4) and possibly check the vacuum pump to see if it's grenaded (?).

Thank you all for your helpful responses.

Vacuum and compression are unrelated on these cars.

A large vacuum leak will sometimes prevent the engine from shutting *off* but will not prevent it from starting.

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1981 Mercedes 300TD, 1994 Honda Civic Del Sol
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I'm not following this. Why the vacuum? There's no relation between the symptoms and vacuum near as I can tell. When you say the engine isn't 'turning over' that normally means it is not rotating at all. Do you mean that or do you mean that it is turning but not firing? When you say 'replaced the fuel' what exactly do you mean by that? Have you cracked an injection line when the engine was turning over to see if it is getting fuel. Have the checked the glowplugs to make sure they are working?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I even have to wonder if a rear cv joint is bad. your description of the sound is unusual. When you pulled the car over and stopped before you shut the engine down was the noise gone? Was it gone when you started the engine again alongside the highway. Or did you just call a tow truck?

Also when you had the car last idling there was no noise until you were well underway. You do have a battery strong enough to turn over the engine now? If not charge it. You might bump the starter a few times to line up the timing marks with some help. Or using the crankshaft bolt is better as you have more control.

It is fairly common for the belt to slip when trying to turn the engine over with an accessory pully nut. I would descibe the noise a bad cv joint makes as a clunk, clunk, clunk. Varying frequency with speed. They can be quite noisey.

How much oil did you have to add to bring the level up in quarts? Tell us. Since you were into the vacuum network take the hose you have on the injection pump shutoff and disconnect it.

You may have got the vacuum lines confused and the injection pump shutoff is now on all the time if vacuum comes up fast enough when you crank.

I almost assume the car will now start. Let it idle if quiet and after it warms up if the noise is still not there try giving it a little fuel to see if the noise is present. Let us know how it is going.

I could easily be wrong about what I have posted. Just humour me a little as what I suggest is very easy to do. Or ignore it if you did not touch the vacuum lines after you brought the car home again from the trip up the street.

It was obvious at that time the vacuum shutoff was functioning properly. Still will be unless again you got into the vacuum lines after that.