I pulled the knocking motor from my 83 240D and decided to purchase a used motor so I can drive the car while I tear into the old motor. The place I ordered the used motor from says that the motors are run tested and also leak down tested before they are sent out.

Heres the problem- I went to do a valve adjustment on the motor and when I line up the cam marks the balancer reads 65 degrees. The balancer on this motor looks slightly different than the balancer on the old motor in that the new one says "PMS" where the old one reads "0/T". Also, when I rotate the engine the guide spring tensioner thing next to the banana slide will move in and out slightly and then pop fully back with a loud metallic "pop". I watched the tensioner on my old motor and it also moves back and forth while rotating but doesn't pop like this one does.

I called the company that sent the motor to ask how a motor with 65 degrees of stretch could run without damage or even be considered a good quality used motor. They suggested I have an experienced Mercedes mechanic look at it to determine if there is indeed a problem before I run it and bend the valves. I asked how they were able to run it without damage to the valves and they replied that since it passed a leak down test there presently isn't any damage to the valves. Should I have someone look at it or am I correct that there is something seriously wrong here?

I think your easiest first check...is to use the 2mm movement of the number one exhaust valve ( do search for particulars ) to see if something like funny is happening with the mark on the cam... there are at least three cams.. maybe some had the mark on different places...
I can't imagine a balancer being able to be put on out of alignment.. but stranger things have happened... so you need to look at that also..
Then perhaps find TDC by using the piston on the compression stroke.. and then mark TDC on your balancer..
Don't assume drastic things are wrong too fast... can cost you a lot of money and effort for nothing...

I just realized that it's 65 degrees before TDC. Also noticed that one of the link covers on the chain is split. How could this motor have been run tested in this condition? I guess if I use this motor I'll need to roll a new chain into it, but if the chain is this messed up what's the rest of the motor like? I've had better luck than this most of my life!

Perhaps the split link coupler is just the fastening for the replacement master link coupling on some replacement chains. Take a really close look as it will either look manufactured or broke with rough edges. Roll the engine through by hand and if no valve interference found consider starting it up. You might want to consider true tdc by finding the true tdc on the first piston but probably very hard to do with head on. But not impossible either as access to piston position possible through small front oil pan removal in my opinion. But what do I know? Just hope provides some relief as about now You are probably about ready to throw a rod yourself.

With a double roller chain there is almost no sidepressure on the chain link ' covers' .... that is why we have been saying that a little bit of peening goes a long way on new chain installations.
I still think that something simple will be found to explain this 65 degrees.... if it were that many degrees off and was run I feel sure there would be serious damage to the piston tops and valves... and maybe the cam and cam towers...
Think positive until you find out differently... maybe someone glued the degree marking on the wrong spot...little things like that can happen in some situations... but at this point I think you need to find TDC by using the number one piston movement.

Just a few more random Thoughts. If pointers on two engines appear to be in the same realtive position try swaping balancers. Should cause no harm. Also you might want to install the tensioner off your old engine as well. The fact the newer one pops may or may not mean anything. If your old balancer indicates 65 degrees off as well after installation send the engine back. There is no way in my opinion the engine would go that far out in the process of being removed from another car and arriving at your place. I expect perhaps this engine may have the wrong balancer on it. Other wiser opinions will probably be posted.

I considered that the chain had been replaced and that the split link cover was the replacement one. The motor appears to have been rebuilt at some point because there is overspray black paint on some parts. However-

Given that a link cover is split, the chain has some very noticable slack in it , the guide rail looks very worn, timing reads off by 65 degrees and the company claims to have leak tested the motor even though the braided fuel loop lines at the injectors haven't been removed I consider this a complete piece of ****. I contacted them and after being passed around for awhile finally got someone who said they would replace the motor and pay for shipping both ways. So we'll see what happens.

Good Deal !
But now we will never know what caused those crazy symptoms.

Here it is-

Broken balancer. One metal pin was shattered to near dust and the other pin was cracked in several pieces. The balancer had spun on the crankshaft and mangled the end of the crank. If the crank wasn't chewed up I would swap the balancer from the other motor. But as it it is there really isn't much left for the pins to sit in. When I lined up the balancer roughly where it should be the timing reads around 4 degrees ATDC, that's more like it.

I also took another look at the split link cover. It seems like someone cut through it and bent it around the pin? Don't know what happened here but it doesn't look good.

"I still think that something simple will be found "----ME

Thanks for filling in the ' end of the story'.....

A nice picture of the chain link would be interesting... MB has used more than one style of chain link... maybe this is one of the really old ones superseded by a Tech Bulletin...

I doubt it's an old style link, the motor's from an 83 but I guess you never know.I think it's someones rebuild job. The motor appears to have been rebuilt. The block was painted and there's overspray on things like the oil filter housing, etc. The motor could have been run in this condition but I'm still firm that there is no eveidence of having done a leak down test. I asked one of the sales people at the company how they do a leak down test on a 240D. They replied they remove the "spark plugs" and pressurize etc. I asked how exactly you remove the "spark plugs" on a 240D without removing the old braided and dry rotted fuel leak line. That guy passed me off to someone else.

Now the real fun will begin. Wonder if I'll see a replacement any time soon. Funny, the only time they were efficient and pleasant to deal with was when I gave them my credit card number

"I asked how exactly you remove the "spark plugs" on a 240D without removing the old braided and dry rotted fuel leak line"--mdlwolf

Just for the record... the Factory Shop Manual shows using the glow plug holes for compression and leakdown tests... not that they did that... but the old fuel lines being in place would not preclude them doing a leak down test.

Would you like to tell us the name of this mystery company that sold you such a fantastic engine?

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

"Just for the record... the Factory Shop Manual shows using the glow plug holes for compression and leakdown tests... not that they did that... but the old fuel lines being in place would not preclude them doing a leak down test."

Even better then since the motor came with the glow plug wiring harness attached to the glow plugs. I would find it strange that they would remove the plugs and then reinstall the old wiring harness. The 8mm nuts were also difficult to remove, not something I would expect if they had just come off.

Yep, you now can be sure they did not do a leakdown. (especially since they talk about sparkplugs )

__________________
'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

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