Need help with timing chain replacement on 450sel - PeachParts Mercedes-Benz Forum

ptoro01 · #1 10-08-2004, 10:08 PM

hey everyone,

I have yet another question. Tomorrow I have the opportuinity to rail through a new timing chain into my '78 450sel. I have heard of many ways in doing it. Please let me know if this is the right way to tackle this one... first I plan to remove the valve covers and check the integrity of the recently installed rails. Then remove the tensioner, and cut 1 link and open it up. Once its open, I have a connecting link with which I will connect that to the new chain. Once there, I will take zip ties and zip tie the chain to the sprocket and turn the engine over slightly at the crank. Then swap out the zip ties and move the engine over another few inches...

Is this the safest way to attempting this. Do I absolutly have to remove the chain tensioner, What should i watch out for, every tip and trick is welcome. I dont want to kill my engine.

Thanks,
Peter

MikeTangas · #2 10-08-2004, 11:44 PM

Removing the tensioner provides much needed slack on the new chain, with the tensioner in place the new chain will appear to be one link too short.

Using zip ties is the method I've used twice. Makes a handy, inexpensive alternative to the "real" chain guide. Make sure to use the ties on both ends of the chain, the new chain going in and the old coming out. The chain must remain in contact with the cam sprocket.

ptoro01 · #3 10-09-2004, 12:05 AM

Thanks for the info, I had that pictured exactly as you mentionned. I figured that was something I needed to do in order to do it right. I will also make sure to remove the tensioner. May I ask how is it that you pushed it back on. I swapped it out and used longer bolts to reel it in but is that the best way to do.

I will post result tomorrow. Hopefully I only have good news...

Peter

MikeTangas · #4 10-09-2004, 12:20 PM

Getting a new tensioner in is a PITA. The tension on the plunger makes it a chore to compress when installing, compiled by the tautness of the new chain. Some tensioners require being primed before installation (my 4.5 required that while the 5.6 did not), priming makes them even tougher to get in. Use both hands to press in, have the bolts close by, once compressed and in you should be able to hold in place onehanded while starting the bolts. Using slightly longer bolts to get started sound like a neat idea.

Tomguy · #5 10-09-2004, 08:42 PM

Quote:

Originally Posted by MikeTangas

Using slightly longer bolts to get started sound like a neat idea.

I did that and yes, it made it MUCH easier to do. Remember to tighten each one uniformly so it doesnt get crooked and then remove one of the long bolts, replace with the original one and tighten it to where the head is flush with the tensioner, and do the other.

300SDog · #6 10-09-2004, 10:33 PM

Small bungie cords too... great for keeping tension as the old chain gets pulled out and the new chain gets fed through. I think its usually considered a 2 man job where one guy turns the crankshaft (after pulling the spark plugs) and the other feeds the chain.

On chain rails, its been said the newer plastic ones can be a little brown, but shouldnt be too dark with age. Cracking of chain rail with bits falling into the gears is worst case scenario.

Older style alloy rails, that can be resurfaced with new rubber tracks, are considered a retro-upgrade over the solid plastic ones. Dunno when they discontinued the alloy rails (1974?) but they should be on everybody's list of rare and endangered interchangable parts worth salvaging from junkyard engines.

ptoro01 · #7 10-09-2004, 11:20 PM

Hey,

Aight I got it through... Then the shop closed on me so Im back at it tuesday. I had to pull the battery, the alternator, the fan and spark plugs. Then I rolled the timing chain through, it went in easy except that I had the neat idea of using short tie wraps so they were a pita to operate. That took me 3 hours to rail it through. When I put everything together is when all hell came loose...........The car started cranking, it went fine didnt collapse any valves or anything but when it started up, it ran fine on all 7 cylinders. One of the was crazy back firing. Now did I just not put one of the plugs back in right or is the whole timing off. I am assuming that one of the plugs is just not getting enough power and once fuel accumulates and a small spark ignites the whole thing it goes boom really loud. This you can really hear from the center muffler and not inside the engine bay...

I did drop one of the plugs and I have 8 more in my closet so I may just replace them all while i am at it. I also forgot the spark plug tool so I had to use the one mercedes gave with the car and that tool is the most worthless thing around.

I will post pictures real soon of what it looked like. But please help me out.

Peter

Tomguy · #8 10-09-2004, 11:48 PM

Definetly broke the plug, or it isn't getting a spark. It isn't chain-related, as the backfiring indicates that it's getting gas to the cylinder and exhausting it properly.

ptoro01 · #9 10-10-2004, 08:01 PM

Thank you everyone for your help. The problem was that I had to hurry to put the fan clutch/shroud, alternator, battery and battery tray, 8 spark plugs and a valve cover in under 30 min. The tool that mercedes provides with the engine is a bad design because the flex joint has a position where it gets stuck and you feel it like the plug is in fully.

This morning I went back to the car and replaced the 1 plug i dropped, and tightened all 8 of the plugs with the proper tool. Almost none of them were tightly installed. Then I started the engine, it was running fine until I reved it up to 2500rpms at which point it started back firing again. I thought about it and started removing spark plug wires while the engine was running. The driver side reacted to every plug being removed but the passenger side didnt. I checked to see if the plugs were in the right place and cyl 1-2-3-4 had wires running to them as 4-1-2-3. Then after switching them, the engine started up and came to life. The idle increased 500rpms so I lowered that right away and it runs very well. I no longer fear starting my engine and it almost seems to run smoother and have a little more power. But what amazed me was that the engine ran on 4 cyl smoothly and only roughed up when it got down to 3.

Thanks for all the advice, another repair that was done properly and I didnt break anything other than a spark plug... HOORAY

Peter

cth350 · #10 10-10-2004, 11:24 PM

running on the "correct" 4 plugs gives you a fuel injected 230.4 instead of a 450sel. -CTH

ptoro01 · #11 10-11-2004, 08:35 PM

What do you mean by that?

Peter