1979 240D checking chain stretch - PeachParts Mercedes-Benz Forum

snapped_bolt · #1 05-30-2016, 06:14 PM

Checking it right now.
Using the "2mm method".

So...If I am looking for roughly .080" motion on the dial indicator, exactly when is that measured? Did I miss the bus? The cam lobe isn't a point, I can continue to rotate the crankshaft an it will "dwell" on .080" as the reading on the balancer changes.
I have noticed as I rotate the crank, the tensioner rail "snaps" and the chain jumps a touch. That tensioner rail is coming out for sure, and I think I need to replace the tensioner as well.
!This timing chain was made in Japan?!?

Incidentally, the cam mark and tower mark are several degrees off from each other. Like about 10 degrees....

I could really use an explanation of that "2mm lift"...

Back to the oily

snapped_bolt

leathermang · #2 05-30-2016, 08:32 PM

Check my signature url....

and ...

http://www.peachparts.com/shopforum/diesel-discussion/162071-diesel-timing-chain-thread.html#post1251434

snapped_bolt · #3 05-30-2016, 11:43 PM

...but I have gone through a lot of them, and I still do not find a "point" to say "I am there". But there is ONE exception- in the FSM dated 1980,
05.4-215/5 :
"8 Continue to turn crankshaft in normal operating direction until small dial gauge pointer has dropped by 2 mm (valve lift) to 1 mm.

At this position, the reading on the balance plate must agree with the specification "intake valve opens". "

Here I have two items. One, this explains where the "2 mm" comes from.
Two, you continue to rotate UNTIL the needle has dropped to 1 mm. Stop right there!

Now I haven't noticed any timing chain instructions on this site that mention this procedure. Just ""2 mm", which as I said before occurs through a segment of the lobe on the cam for several degrees. Which by what I have seen written would put folks in the station, but they would still miss the train.

Or...procedures recommended by my FSM have been annulled by new information.

Either way... it is looking like this chain will be coming out. I will install a new tensioner and tensioner rail and take measurements. If they don't look good, I'll put in a new chain.

After getting a better look at the tensioner rail today it looks like a "no-start" until I get the parts replaced. Not only is the top end of the tensioner worn down, it is crumbling away, about 5/8" x 3/4" worth of the cam side of the rail. The pan will be coming off for this one. I have theorized (perhaps incorrectly) that the failed tensioner has allowed the chain to "whip" like a snake; taking an "s" shape as the tensioner spring bounces against the flailing chain. The only other way for the heavy wear on the end to occur would be for the tensioner to overdrive the chain, causing the heaviest wear at the end.
Suffice it to say I have had enough of this malarkey and the show is over ontil I get some new performers on the stage.

Later

snapped_bolt

leathermang · #4 05-31-2016, 01:40 AM

The thing is , in trying to visualize what is happening, you need to start at the very first to tell us what you have already done...
perhaps pictures would help....
can't just start in the middle and trust that an answer to what you should be looking for is correct.... like how did you zero out the ' slack' ? Is your micrometer set up correctly ? I think pictures are needed... well lighted... in focus and close up... to keep from taking a chance on misleading you....

leathermang · #5 05-31-2016, 02:20 AM

Do you set the micrometer to 3 mm
then move the engine until the ' zero backlash' valve has been opened 2mm..
meaning that your mic has moved down to the 1mm position...
that is where you stop....
I am worried that you have not zeroed out the backlash ....
can we have a pic of your starting position ?

by mentioning the cam lobe not being a point... I am worried that your starting point conceptually is WAY OFF..
you are supposed to be dealing from the flat bottom of the cam lobe.... are you sure you are on the correct valve, etc... so as soon as you have measured 2mm movement of that zeroed out valve... that is where you ' stop' ....

Stretch · #6 05-31-2016, 02:44 AM

I think he's confused about starting at 3mm and stopping at 1mm too

It is quite easy to get confused with this section of the FSM - do a different pre-load - start at 5mm and stop at 3mm then the numbers don't get so easily muddled up. (Or do 4mm and stop at 2mm if it makes you feel better!)

leathermang · #7 05-31-2016, 02:59 AM

The FSM is written by a non native American speaker after being written in German ... with assumptions that a person has been trained by MB school first I think... they leave out a lot of stuff.. often it is good to also have the Haynes manual ... which often has better pictures.. but the Haynes manual alone totally leaves OUT all sorts of warnings the FSM has in it....

snapped_bolt · #8 06-01-2016, 05:58 PM

I wasn't expecting so much entertainment from the timing chain.
As I was cranking away on the ratchet, the chain kept snapping. After the measurements, I took the ratchet for a spin and watched the motion of the tensioner/rail/chain. I concluded this might be great for a Rube Goldberg device, but I really didn't want my car doing these stunts while the engine was running.
As I cranked, the tensioner would retract until it was nearly completely collapsed, then it would *snap* fully open, then return to contracting. I could not only envision this happening as the engine was running, but I could see imminent failure in the making.
While the tensioner is not designed to perform it's duty while the engine is not running, the action I witnessed was unnerving.
And some might say this is appropriate.
The problem is the destructive wear concentrated at the last 25-50 mm or so of the tensioner rail. It is worn THROUGH the metal on the engine side, and the metal on the front is beginning to wear.
To begin my solution, I will install a new tensioner, tensioner rail, and oil pan gasket since I now need to go fishing for debris. Somehow, some way an image will be uploaded...

Cheers,

snapped_bolt

leathermang · #9 06-01-2016, 07:06 PM

Looks like you are on the right track...

snapped_bolt · #10 06-01-2016, 10:01 PM

Something has got to give. To me it makes no sense firing it up the way it is.
Once the new parts are on I can try cranking the pulley bolt and see if I can concentrate- that chain snapping would make it impossible to creep up on 2 mm, the cam also lopes over suddenly as if it has built up compression....
Anyway, the oil in that engine doesn't smell fresh, so a short changeout will help. I do not care for the aroma of oil that should have been retired coming from the inside of the engine.
So, who has installed an EZ Drain on their oil cooler? How much is trapped in the cooler lines when the oil is drained through the pan?
I remember ages ago my great-uncle pulling into the Richfield station. Up goes the hood... and invariably the attendant would inform him that there was no oil in the engine. He would then step out and politely remind the attendant that "clean oil looks just like that!" It was clean because of regular 3000 mile oil changes. That was on the '52 Lincoln Capri. With Circle C 30-weight.
Man. I have issues with dirty oil. Even if it is "normal" for the vehicle.

Waiting on parts. This sucks.

snapped_bolt

leathermang · #11 06-01-2016, 10:27 PM

Take the glow plugs out, use the CRANK Bolt to turn it... FSM forbids using the power steering nut to turn over the engine.... LOL... and I understand that last sentence will make you cranky.....

snapped_bolt · #12 06-01-2016, 11:31 PM

Page, copyright date, please!

I know better than use a driven pulley to drive a chain.
I have been turning the crank bolt. That is what makes that chain so disgusting- it's right there in my face as I lean over the radiator to crank.
Gymnastics are great. Dance is a dream. Gyrating timing chains are nothing but a loathsome plague. Flailing away before me, expecting me to button it up and drive on until the engine has been liberally adorned with crispy component kibbles that can be removed with a vacuum.
Engines should not be recycled from the inside out.
I have no burning desire to go on an "NOS hunt". I choose LIFE for this engine. And I'm not talking cereal.

Ha.

snapped_bolt

leathermang · #13 06-02-2016, 12:54 AM

Quote:

Originally Posted by snapped_bolt

...... I can try cranking the pulley bolt ...snapped_bolt

Sorry, took that to mean power steering pulley bolt...rather than crank bolt.

snapped_bolt · #14 06-05-2016, 10:19 PM

And the car is not happy.
When it idled before the job, it seemed a little fast, and there was a shake.
Some PO apparently advanced the injection pump to make it run better.
I did find a 0-degree key on the camshaft, I should have room for adjustments of the chain if needed.
My 6mm pin puller was an exhaust spacer for a 2003 Cummins.
I pulled the lower timing chain tensioner rail off the harmonic balancer. The crank pulley remained. I put a nut and two washers on the 8mm bolt, tightened it, then ran the nut down to the pin. I drove in the pin with a drift against the washers.
Would have been great it she fired right up, but I was leery of that injection pump setting.
Stopping for the night, it was hot here today. Back to it tomorrow!

snapped_bolt

leathermang · #15 06-05-2016, 11:02 PM

Did you set the injection with the Drip Method ?