How much change is normal? - PeachParts Mercedes-Benz Forum

krwsenior · #1 11-29-2014, 10:17 AM

I don't have the proper tools to check the timing correctly, so all I have to go by is the timing marks. Before starting on rolling in the chain, my mark at the crank indicated 10 degrees before TDC. After the chain replacement, I have 9 degrees after TDC. Does this sound reasonable? I need some reassurance.
I don't think the chain has ever been changed - 328k miles. OM603. 1991 350SDL.

leathermang · #2 11-29-2014, 11:27 AM

Doing things like this without the proper Factory Shop Manual..and reading it..... and the proper tools...is taking a chance on causing HUGE expensive problems for you and your car....

krwsenior · #3 11-29-2014, 11:54 AM

I don't disagree with that statement. I have a tendency toward "oops". However, I did spend hours reading, mostly on this forum how to do this. It seemed simpler than it actually was.

Diesel911 · #4 11-29-2014, 12:19 PM

I can't remember the specifics but I think someone mentioned that being one tooth off was worth X amount of degrees.

Also in your First post it was not possible for your your reading to have been "10 degrees before TDC".

When the Engine was built it was set at OT (top dead center) and as the Timing Chain Stretches and the Gears were the reading is after top dead center. If the Engine was running normally I don't see a way for the Chain to have gone before top dead center.

Diesel911 · #5 11-29-2014, 12:22 PM

Quote:

Originally Posted by krwsenior

I don't have the proper tools to check the timing correctly, so all I have to go by is the timing marks. Before starting on rolling in the chain, my mark at the crank indicated 10 degrees before TDC. After the chain replacement, I have 9 degrees after TDC. Does this sound reasonable? I need some reassurance.
I don't think the chain has ever been changed - 328k miles. OM603. 1991 350SDL.

I forgot to as what the Gear Teeth looked like becaue it is not just the Chain that wears.

leathermang · #6 11-29-2014, 12:44 PM

for the 617 ... 18 degrees..
here is the problem with trying to do it just reading on the forum...
and I have said this many times before...
and it comes from the fact that I own almost all the paper manuals...and have read them...
THERE ARE MANY MANY WARNINGS IN THE FSM WHICH NEVER EVER GET MENTIONED ON THE FORUMS... NOT JUST THIS FORUM.... ACROSS THE INTERNET....

' oops' on an interference engine can really be expensive... as the valves can contact the pistons and all sorts of things get bent... including perhaps the cam... not an engine to guess with...unless you are a masochist with a lot of money...

krwsenior · #7 11-29-2014, 06:04 PM

I was reading the degrees as "before" because as I turned the engine, these marks were before reaching OT. Error on my part, sorry. So to be correct, the cam alignment before changing chain was 10 degrees after TDC. After changing the chain (and I'm certain that I corrected my slip of teeth on cam sprocket), the mark is on 9 degrees before TDC. This seems like a lot of stretch in the old chain. I'm not sure that the pointer is in the right place and giving accurate information, but the change is certain.

The car runs great, as it did before. I can tell a slight difference in performance for the better, but not much. It runs very smooth and accelerates like a gas burner. Performance much improved when I changed the injector nozzles and balanced them a few months ago. ALDA is set to stock location. (I had adjusted it 1.5 turns but put it back to stock when rebuilding injectors).

I also replaced the factory (I think) vacuum pump with a used one that has the upgraded bearings. Just looking at those ball bearings is worrisome. I'm glad that is out of the car.

leathermang · #8 11-29-2014, 06:15 PM

That is why you find tdc by observing and measuring the number one piston.
then use the 2mm movement of the number one intake valve....
then use the drip method to get the relative injection properly set...
You can get lucky and things run well...
but without doing it from the basics you do not know how much better it might be able to run...

Lucas · #9 11-29-2014, 08:30 PM

Edit: I don't know.

krwsenior · #10 12-11-2014, 08:30 PM

Update: Engine is "ticking" under acceleration and at highway speeds. Not very loud, (if radio is on at low volume can't hear it). There is also a "rattle" while idling that is fairly loud. So my decision to change the chain without checking the timing was a bad one. Still running very good.
I've searched with a stethoscope all over the engine but I'm having a hard time finding the tick because it doesn't make the sound at idle. #6 injector is a little louder than the others so I switched it with #5 and slightly louder sound seemed to stay with #6 cylinder (listening on injectors). I can't distinguish the rattle to any certain point either.
I would like to read and follow the manual to check/adjust the timing. I have a link to the star tek manual but can't find this procedure on there. I have a dial indicator, but I will need a way to mount/secure it. I also will need a drip tube??
Can someone give me guidance and a link to the proper procedure/manual? I've read threads till I'm blue in the face. Thanks.

300TD1982 · #11 12-12-2014, 03:30 PM

Quote:

Originally Posted by krwsenior

Can someone give me guidance and a link to the proper procedure/manual? I've read threads till I'm blue in the face. Thanks.

I only have the Factory Service Manuals for the w123, so I'm not sure what Mercedes published for your car. Perhaps the folks at 1800Mercedes would tell you which manuals they printed?

I found my manuals on the for sale section of peachparts. I almost bought them on ebay, but found a better deal here.

For the w123, Mercedes provides online versions of their manuals, but the image quality is very poor. Perhaps there are similar manuals online for your car.

Good luck (never mind, don't rely on luck

)