Steve Brotherton/engine rebuilders help!--big mistake replacing 85 300D Timing belt

[Carrameow]

I HAVE DROPPED BOTH ENDS OF THE CHAIN INTO THE ENGINE and WORSE I HAVE SHEARED OFF THE FIRST 1 or 1.2 cm OF THE LOWER SLIDE RAIL BEARING BOLT!! If you check my website, through luck and lots of work I've been fairly successful at rebuilding engines, but this time I let my daughter help. After cutting the link on the old chain, I walked away to find that she had dropped both ends of the chain into the Front Engine housing. I tried using piano wire to retrieve them, no luck.

(1)!Worse, I sheared the lower bearing bolt on the Plastic Slide Rail while trying to "screw" it out using a metric bolt with the intention of adding more and more washers under the bolt head instead of using a slide hammer. I sheared off the first centimeter of the lower bearing bolt, and the remainder is still there in the cylinder head cover. I'm not sure if I should drill it out, or just leave it alone, and use the remaining portion. I want to fix this the right way and not have to worry about this bearing bolt breaking some day. HOW CAN I RETRIEVE IT/ REPLACE IT?

(2) Now the chain is in the bottom of the engine. I have not turned the Crank or camshaft yet. My intention is to remove the Vacuum Pump to reach it. How do I get the chain out--whats the best approach?

(3) Any ideas. WHAT DO I DO ABOUT THE SHEARED BEARING BOLT FOR THE SLIDE RAIL? Its still in there rock solid, but i would prefer to get it out and do a good job. HOW DO I RETHREAD a NEW CHAIN now that the OLD ONE is SITTING DEEP IN THE ENGINE?

confused:

[JimSmith]

Carrameow,

Wow, I read this earlier today and noticed no one has offered any help. I recognize the feeling you are experiencing and truly feel for you. I know that doesn't do you much good so I got my manual out for my old 1975 240D which covers the 615, 616 and 617 engines to look at the situation. While I do not want to make light of the problem, I do not think it looks all bad.

First, one end of the chain is most likely draped over the intermediate sprocket which serves as the injection timer, which a a sprocket about the size of the camshaft sprocket, but located in the bulge on the driver's side of the engine block, with the top of the sprocket and likely that end of the chain just below the head parting line. This area is being obscured from your view and therefore your access to get the chain by the inner and outer slide rails that guide the chain as it comes off the camshaft gear (sprocket) on the driver's side of the engine at the top of the head (if the vale cover is off you can see these items as they stick up nearly half way up the camshaft sprocket). I believe with this assembly removed you will find one end of the chain. My manual suggests this is relatively simple, you loosen the screw that is behind the arm connecting the inner slide rail to the outer one and it should slide forward enough to be removed.

Anyway, once you get an unobstructed view to see if the chain is actually slumped over the intermediate sprocket, you have to be very careful not to disturb things and let the chain just fall all the way into the oil pan. If you can reach the chain and avoid letting it fall further you may have saved some further disassembly to get to the next set of slide rails just before the chain gets to the crankshaft sprocket on the driver's side. At this point if you are lucky (and sadly you don't sound lucky) you may also be able to recover the other end, as it may be piled up on top of the crankshaft gear. With the driver's side end secure you can go after the other end. Be careful as I think the chain may just slide all the way down to the oil pan and if that happens you have to do lots of disassembly to thread the chain back into its path.

To get the other end of the chain if it is visible but out of reach you will need to remove the chain tensioner and likely the big tensioning rail on the passenger side of the engine. This is the baby with the broken bearing pin, I believe. To do this job you must have the radiator out and the cranshaft balancing wheel and belt pulley off. Personally I would buy a new pin, and then drill out the old one enough to tap a thread into what is left of it and use a puller to get it out. If that fails again, I think you have to drill it out and then deal with the debris inside the engine by flushing and removing the oil pan.

If you have to go through the oil pan to get to the passenger side end of the chain, you can drop a wire or the like down and tie it to the end of the chain and pull it up. That side of the chain path is simple, no two sided guides or anything, just a straight shot up past the tensioning rail to the camshaft sprocket.

If the whole chain is in the oil pan, I would take the car to a shop with Mercedes experience and have them finish the job. There are special tools and the like required to reassemble items that have to be timed and so on to make it work right.

I hope this helps and would be glad to help if you have questions I can get answers from in this manual. Jim

[JimSmith]

Carrameow,

Wow, I read this earlier today and noticed no one has offered any help. I recognize the feeling you are experiencing and truly feel for you. I know that doesn't do you much good so I got my manual out for my old 1975 240D which covers the 615, 616 and 617 engines to look at the situation. While I do not want to make light of the problem, I do not think it looks all bad.

First, one end of the chain is most likely draped over the intermediate sprocket which serves as the injection timer, which a a sprocket about the size of the camshaft sprocket, but located in the bulge on the driver's side of the engine block, with the top of the sprocket and likely that end of the chain just below the head parting line. This area is being obscured from your view and therefore your access to get the chain by the inner and outer slide rails that guide the chain as it comes off the camshaft gear (sprocket) on the driver's side of the engine at the top of the head (if the vale cover is off you can see these items as they stick up nearly half way up the camshaft sprocket). I believe with this assembly removed you will find one end of the chain. My manual suggests this is relatively simple, you loosen the screw that is behind the arm connecting the inner slide rail to the outer one and it should slide forward enough to be removed.

Anyway, once you get an unobstructed view to see if the chain is actually slumped over the intermediate sprocket, you have to be very careful not to disturb things and let the chain just fall all the way into the oil pan. If you can reach the chain and avoid letting it fall further you may have saved some further disassembly to get to the next set of slide rails just before the chain gets to the crankshaft sprocket on the driver's side. At this point if you are lucky (and sadly you don't sound lucky) you may also be able to recover the other end, as it may be piled up on top of the crankshaft gear. With the driver's side end secure you can go after the other end. Be careful as I think the chain may just slide all the way down to the oil pan and if that happens you have to do lots of disassembly to thread the chain back into its path.

To get the other end of the chain if it is visible but out of reach you will need to remove the chain tensioner and likely the big tensioning rail on the passenger side of the engine. This is the baby with the broken bearing pin, I believe. To do this job you must have the radiator out and the cranshaft balancing wheel and belt pulley off. Personally I would buy a new pin, and then drill out the old one enough to tap a thread into what is left of it and use a puller to get it out. If that fails again, I think you have to drill it out and then deal with the debris inside the engine by flushing and removing the oil pan.

If you have to go through the oil pan to get to the passenger side end of the chain, you can drop a wire or the like down and tie it to the end of the chain and pull it up. That side of the chain path is simple, no two sided guides or anything, just a straight shot up past the tensioning rail to the camshaft sprocket.

If the chain is in the oil pan, I would take the car to a shop with Mercedes experience and have them finish the job. There are special tools and the like required to reassemble items that have to be timed and so on to make it work right.

I hope this helps and would be glad to help if you have questions I can get answers from in this manual. Jim

[JimSmith]

Sorry about the double post. I tried to edit the post to add the word "whole" while describing the chain in the near last paragraph, and somehow got two posts in a strange order. Once the whole chain has left the path on the driver's side of the engine and is sitting in the oil pan or below the crankshaft gear/sprocket, it is a lot of work with things like the injection pump timing requiring know how and tools that I surely don't possess so I would tow it to someone who does. Jim

[Carrameow]

Thanks for your help, Mr Smith. I am taking tomorrow off, I guess this weekend is spoken for!

[JimSmith]

Good Luck! Jim