another chain question - PeachParts Mercedes-Benz Forum

wade · #1 02-10-2006, 12:42 AM

hello again!!! trying to get my old 240D on the road (actually the car runs great)I did the valve lash last night and took a look at the chain stretch using the rough estimate.....ie cam and balancer marks. i know that the 2mm method is the best to use,but my initial test results baffled me. with the cam marks as perfectly aligned as i could get them, my reading on the balancer was almost 12 degrees!!!! is this possible? keep in mind that the car runs very well,starts great,no black smoke etc etc. also, in reading some recent threads,and pics,using this rough method,it seems like all the degrees marks were in reference to ATDC and my marks are BTDC.......so is a badly worn chain suppossed to read after or before TDC. the car has approx 250 000
miles on it. And i will try to do a proper 2mm test on it but it wont be for awhile.....just looking for some input on what seems to be a very large chain stretch......also one last question, are the woodruff keys that fit the 300 the same as the 240?,i have a couple spare keys from my 300 kicking around.....
thanks guys!!!

signalredcoupe · #2 02-10-2006, 08:53 AM

I don't have the manual in front of me, but I assume that if the mark on the cam is aligned, the harmonic balancer should read 0 degrees? Then a stretched chain should indicate a late reading on the crankshaft i.e. degrees after top dead center, Paul.

___________________
'84 300CD 290,000

dannym · #3 02-10-2006, 09:32 AM

Quote:

Originally Posted by wade

hello again!!! trying to get my old 240D on the road (actually the car runs great)I did the valve lash last night and took a look at the chain stretch using the rough estimate.....ie cam and balancer marks. i know that the 2mm method is the best to use,but my initial test results baffled me. with the cam marks as perfectly aligned as i could get them, my reading on the balancer was almost 12 degrees!!!! is this possible? keep in mind that the car runs very well,starts great,no black smoke etc etc. also, in reading some recent threads,and pics,using this rough method,it seems like all the degrees marks were in reference to ATDC and my marks are BTDC.......so is a badly worn chain suppossed to read after or before TDC. the car has approx 250 000
miles on it. And i will try to do a proper 2mm test on it but it wont be for awhile.....just looking for some input on what seems to be a very large chain stretch......also one last question, are the woodruff keys that fit the 300 the same as the 240?,i have a couple spare keys from my 300 kicking around.....
thanks guys!!!

HEy Wade,
You should be reading ATDC. A normal reading will be around 2-2 1/2 degrees ATDC.
It's been my experience that the cam marks are inacurate. Even the smallest bit off will through off your reading. Though other people seem to have success with it.

Quote:

as perfectly aligned as i could get them

They have to be perfectly aligned...period! Close as I can get it is not good enough.

The fact that you say it "runs great" would tell me that it can't be too far off.
I wrote up a tutorial here:
The proper way to measure chain stretch
It shows both methods of checking the chain.

The dial indicator and magnetic base are very cheap to buy.
www.harborfreight.com
Why don't you get a set and try the 2mm valve lift method?

Danny

wade · #4 02-10-2006, 10:10 AM

i am getting a dial setup today and will post results.......I thought that the mark method was a good indicator to let you know if your chain is streched,and then you could proceed with the dial check to estimate the correct key that would be needed?i realize that very little movement of the crank moves the mark alot,but if i am lining these marks up the best that can be done with the human eye(which i am thinking is very close) how could i be out that far? and also on the wrong side of TDC? what else could be wrong?
also, will my old 300 woodruffs fit in the 240?

dannym · #5 02-10-2006, 11:06 AM

If those marks are lined up that close your readings shouldn't be so far off. When you check with the dial indicator hopefully we can come to some kind of conclusion.

I don't know about the keys. You can look up part numbers for your 300 and see if they match the part numbers for your 240.

Danny

Stevo · #6 02-10-2006, 01:04 PM

Quote:

Originally Posted by wade

my reading on the balancer was almost 12 degrees!!!! is this possible?

The reading is taken ATDC and.... yes its possible to have a chain that bad and still have a car that runs good. Someone could have just advanced the IP (bumped it toward the engine) Look for a chisel mark where the IP and block meet. That would have been put there as a reference for moving the IP. It might indicate if its been advanced.

I wouldn't worry about keys, replace the chain, You proly dont need a more accrete reading either

wade · #7 02-10-2006, 11:21 PM

OK...here's the deal. just came in from the garage after doing about 5 dial indicator shots on the #1 intake and here are the results.616.012 engine with a number 10 cam. every one is coming up to about 2 degrees BEFORE tdc.
used chain spec should be around 11 degrees...so once again WHAT IS WRONG with this picture? car is running great,but now this is driving me crazy

Here is one other oddity....when i am turning the crank,there are several "dead" spots in the turning of the cam....ie, the crank keeps turning but the cam stops. then if you continue turning the crank the cam will grab again and continue with the crank"hope this is making sense". is it possible that this chain could have skipped a tooth at one point, and someone just adjusted the IP to make it run? why the strange reading and also why before tdc and not after?

HELP!!!! waiting with greasy hands

wade · #8 02-11-2006, 12:41 AM

so i just mabe discovered something else. is it possible that either i have been using the wrong timing mark, or someone else lined up tdc and the cam tower mark to the wrong pointer? my past car (300D) i was using the pointer that is right over the crank dampner, the same one that dannym's pics refer to. that is also the one that i am using on this car (240). this car also has the
other holder/pointer that is situated to the left of the one i am assuming is the proper one. i think it is for the inductive pick up for the timing, if you have the special tool. it is a square device with a round hole in it,and you can see the dampner numbers thru the hole. Reason i bring this up is that when i do the dial test i come up with a number of about 14 degrees ATDC,if i look at the number that is right in the center of that hole. Also, if i line up the cam washer and tower mark, i am reading about 4 degrees ATDC, once again when looking thru the hole in the other pointer.both of these numbers make sense..........so have i been looking at the wrong pointer all this time?
or is it just way too late to be in the garage

mercedesmatt · #9 02-11-2006, 12:58 AM

be sure your turning the crank the right direction!!!!! engine rotation is clockwise facing the front of the engine. sounds like your turning it counter clockwise and the tensioner is bouncing. throwing your readings off.

Stevo · #10 02-11-2006, 01:59 AM

Quote:

Originally Posted by wade

,if i look at the number that is right in the center of that hole. Also, if i line up the cam washer and tower mark, i am reading about 4 degrees ATDC, once again when looking thru the hole in the other pointer.both of these numbers make sense..........so have i been looking at the wrong pointer all this time?
or is it just way too late to be in the garage

Its not the center of the hole, its the "knife edge" your spoz to use.

wade · #11 02-11-2006, 10:50 AM

i am not turning the engine backwards (counter clockwise). i have discovered that if i keep tension on the chain,with slight pressure on the chain tensioner,there are no more dead spots,so i may have a weak spring in the assembly,but i know now that this is not effecting my reading. I have done another 3 or 4 readings this way and there is no difference.

The reason i think this car is different is that my 300 parts car out back
has the knife edge pointer to the left of the one with the hole in it.....the service manual pics and the haynes manual also are depicted in this way....and lastly, dannym's pictures also have the inductive pickup to the right of the edge pointer. on my 240 the EDGE POINTER is to the right of the
pick up or circle indicator, seems like the only one that is like this.....
Can someone else shed some light here? Iam going out to take a picture of it and will post it.

wade · #12 02-11-2006, 02:53 PM

ok, here's the pics.had trouble resizing,hopefully it is clear enough to see.
this is the position with the #1 intake 2mm engaged....comments

dannym · #13 02-11-2006, 05:11 PM

Wade,
Can you verify the engine number on the side of the block?
Also if you can verify the cam code too.

The specs for your engine (1978 240D)are here:
http://mb.braingears.com/123_DISK1/program/Engine/M115/05-215.pdf

As you can see it doesn't list a cam code #10 or the engine number you posted.
Very bizarre!

Danny

wade · #14 02-11-2006, 05:50 PM

I actually got the numbers from your thread with the pics (nice job by the way)

For Engine(s) 615.940 (44kw), 616.912 (53kw); Camshaft code 10, specs are:
With new chain 9 degrees ATDC.
With used chain (from approx. 20,000 Km) 11 degrees ATDC

wade · #15 02-11-2006, 06:03 PM

just checked the skinner box on line manual and the specs are listed for the 616 912 with the 10 camshaft.same numbers you mentioned in your thread