hi there
do I have a fun one for you...


I recently got a 1982 mercedes 300td

it wasnt doing so good, and there was an engine knock ... but I thought I could handle it.



its sadder yet simpler to post this in retrospect:
knowing that the engine knock I've been hunting for this whole time was the vacuum pump bearing working its way loose and finally going on a rampage inside the engine on the highway



as I understand the aftermath:

the engine crunched the ring and spit it out and seem to have skipped timing. as a result it will now only turn manually part of the cycle. The chain from what I can see seems to still be intact.


the million mile question:
can I just loosen the cam shaft sprocket and try to bring it back into timing to get a clearer idea of what else may have gone wrong?
what are other ways to check for possible problems short of removing the head?



thankx in advance for any help


S

Yes, try to get the chain back in time which may require removing the rocker arms to completely close the valves. Then put compressed air in the cylinders using a compression test gauge adapter to see if there are leaks and where they leak.

Worked on two 240D's with broken chains that broke the cam tower/supports but did not bend valves so removing the cylinder head wasn't necessary. Both ran again for a long time.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Subscribed, here's hoping it'll come out O.K.......

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Something else to check: 2 Vacuum Pumps destroyed timer Bushing Identified as the problem
http://www.mbca.org/forum/2013-12-29/why-are-these-vacuum-pumps-being-destroyed

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84 300D, 82 Volvo 244Gl Diesel

Did the cam face of the timer suffer any damage?

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84 300D, 82 Volvo 244Gl Diesel

For the time it takes. I would disable the valves and do a leak down check. These are interference engines and you might have bent some valves. Also inspect for broken cam towers or broken cam.


You are likely to have to disable the valves to get the cam timing back anyways.

theres some scoring on the timing cam face but not much (tried to attach image)
the cam shaft itself seems ok


I checked and there doesnt seem to be any play in the timing device
the chain isnt loose or stretched at all either



so far im having a hard time following all the steps...( tensioner, SLS pump, guardrail)... just to get to removing the sprocket off the camshaft


it really helps to remember the engine is likely shot anyways when I get that familiar feeling I might be making a big mistake by trying to do it myself


thankx for the pointers though

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The timing chain has a tensioner so it should not be loose. I am not sure if the in and out end play can be checked with the Timing Chain Tensioner tensioning the chain.

I am also not sure if you can feel the end play. The manual calls for the use of a dial indicator to check the end play.

There is supposed to be some end play to begin with.

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84 300D, 82 Volvo 244Gl Diesel

Personally I would have started by removing the Valve Cover and looking for those broken Cam bearing Towers or other damage up top.

Assuming the Timing Chain was still on the gear teeth I would have rotated the Engine in the direction of normal rotation and lined up the timing marks behind the Camshaft Gear and on the first bearing tower and then looked down at the what degree marks the pointer is pointing to.

What info I got from that would help me decide what to do next.

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84 300D, 82 Volvo 244Gl Diesel

sure... had to do that to get to the chain
maybe I wasnt specific before...



on first look everything seems intact both under the valve cover and looking up through the bottom


except:
rotating the engine manually only goes part of the cycle

the difference between the camshaft TDC marks and the lower pointer is about 30deg

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The above in red is likely why the engine is hanging up. One of the Pistons is hitting a valve because the camshaft timing is now way off.

What get the Crank shaft orientated to OT (top dead center). Remove the Timing Chain Tensioner Spring and remove the Timing Chain Tensioner and pull out the plunger (If the plunger is retching type there is going to be a circular spring that only allows the plunger to go one way). Set that aside.

At that point I don't know how much play is in the Timing Chain. Next would be as suggested by an other member removing all of the Camshaft Tower Bearing Bolts so the Camshaft can be rotated and to line up the timing marks before you re-assemble the Camshaft Bearing Towers to the cylinder head.

If there is not enough slack to do that due to the Timing Chain you would need to remove the Timing Chain Gear.

You re-install the Timing Chain Tensioner Housing followed by the Plunger, Spring, Crush Washer and end Cap and look down and see the degrees. You might have to rotate the engine a bit to line up the Camshaft Timing Marks. Anyway you should end up with the Camshaft Timing Marks liked up with OT or out to 6 degrees or so after OT. At that point if no valves are colliding with pistons you should be able to rotate the Engine without it stopping.

If after the Camshaft is timed and hand cranking still stops it; it is likely there is a bent valve.

With all of the above stuff you could end up with the Fuel Injection Pump put of time. You would need to pull the Pump (replace the front gasket) and stick the pump back in with the Timing Marks on the Fuel Injection Pump itself lined up.

Repair Links

Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

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84 300D, 82 Volvo 244Gl Diesel

thanx
im in way over my head here so any input helps.


Ive been trying to figure out if theres a way to tell the IP timing by looking at the cam face that drives the vacuum pump when the cam marks are lined to TDC



it is my suspicion based on very loose evidence and guesswork that the lower crackshaft sprocket which crunched the ring and jumped timing.



which in my mind would mean the IP and camshaft are still time synched and after I manage to gain some slack on the chain I should rotate the bottom crankshaft sprocket only.



is that even possible? adviseable? or should I focus on rotating it from the top camshaft sprocket side and fix the injection timing later?


thankx for the input

S

These things tend to be kind of procedural. Not following the procedures means once in a while you have good luck but most of the time you spend a lot of time and work and end up having to follow procedures anyway.

An extra issue is that if you get lucky this time you don't learn much.

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84 300D, 82 Volvo 244Gl Diesel

You have to do things in some logical order. Disable the camshaft from moving the valves. Then do a leak down test of all the cylinders Until you have checked All the cylinders for bent valves.

You can use a leak down tester and air supply. Or just compressed air listening for it escaping any cylinder. Anything else is not first on the list. There is the smallest chance you did not bend valves as the chain did not totally break.

Any concern about where the injection pump is at this early. Does not matter very much. You can do nothing as long as the valve train is intact anyways.

As said there is the smallest chance you did not really damage a valve. That means there is more of a chance you have.

If you have no cylinder leakage only then do you start getting concerned about other things in general. Just in case you do not know. With the valve train disabled. All cylinders can be tested for abnormal leakage without moving anything. Other than the air supply from cylinder to cylinder.

There is absolutely no way to do anything really without disabling the valve system anyways. It is not like there is any another option. Remember you must number all the cam followers as they have to all go back in their original positions.

It was always my understanding that in order to perform an accurate cylinder leak down test that the piston must be at TDC for each individual cylinder with both valves closed. If you hear air escaping from the exhaust you have a bent/cracked/not seating exhaust valve; if you hear air escaping from the intake system you have a problem with the intake valve; if you hear air escaping from the oil fill hole you have either bad rings or a damaged piston.