Please check my work 617.951

[rp930]

I am both knee and elbow deep into this amazing piece of machinery. I am at 207,000 miles. This post is about Timing Chain Elongation. I followed the FSM using the 2mm (0.080) test for TDC. I had a feeling I would be out of spec, but had to verify. I went past 0.080 by 0.004, but I think I will still require a new chain. I ask for opinions on new chain, Cam sprocket. Banana Guide appears good, I will pull and check plastic guide before parts are ordered. No woodruff key installed. Be gentle I'm old.

[Mike D]

8-10 degree stretch is considered the usual maximum. Don't trust just one measurement. Crank it around again and re-check.

[engatwork]

Nothing to roll chain in. If you can use a ball peen hammer you don't even need any special tools.

[rp930]

Thanks Jim, does the sprocket look ok.

[hercules]

Originally Posted by rp930

I am both knee and elbow deep into this amazing piece of machinery. I am at 207,000 miles. This post is about Timing Chain Elongation. I followed the FSM using the 2mm (0.080) test for TDC. I had a feeling I would be out of spec, but had to verify. I went past 0.080 by 0.004, but I think I will still require a new chain. I ask for opinions on new chain, Cam sprocket. Banana Guide appears good, I will pull and check plastic guide before parts are ordered. No woodruff key installed. Be gentle I'm old.

That"s a lot of stretch,just did mine two days ago. 200,000 thousand,meaused
11 degrees atdc,replaced chain now 9 degrees,added 4 degree key,now
5 degrees just where I wish.
Be sure dial gauge is measuring completely vertical and clearance is removed
from cam.
Cam gear is worn, but never seen one break a tooth,other gears worn just as much! How to tell,either tip of gear pointed or large u at bottom of gear,
which you have, I would replace.

[rp930]

Clearance is removed, will check angle on dial stem, and retest. Just removed T-stat housing to get to tensioner. Fan removal will aid getting to crank bolt. Water pump housing bolts leak oil. How is that sealed.

[hercules]

Remove bolt apply sealer reinstall'

Cam gear is farthest out of the oil will be usually worn the most. Don"t wish
to cause undo concern.

[rp930]

Good point, the parts list grows.
Vacuum pump housing
VP bearings
Timing Device Bushings
VP Gasket
Oil pump Bushing
OP Pin
OP Tensioner
OP Spring
Oil Cooler Repair Fitting
Timing Chain Tensioner Spring
TCT Gasket
TCT Seal Ring
TCT End Spring
Timing Chain
Cam Sprocket
Valve Cover Gasket
Oil Pan Gasket

Back to work.

[Stretch]

[My comments in response to a PM request for intervention]

If you are worried about timing chain position I recommend you take your time and make sure you know where you are.

TDC is "shown" on the crank pulley as zero degrees but you need to work out where you are in the four stroke cycle. There is a notch on the camshaft that can help - you need the TDC shown at the crank to be more or less the TDC that shows the position at the camshaft.

Note the notch isn't reliable as a "safe position" on a chain that has been used. As said above you need to spin the crank (not power steering pulley or camshaft!) a few times to make sure everything is aligned nicely.

Finding where you are in the four stroke cycle is a crucial part of the 2mm lift test which is the only reliable way of measuring timing chain adjustment on these engines.

Don't be tempted to turn this timing chain system in an anti-clockwise direction (chain can foul and it messes up your measurement)

Remove glow plugs to help your fight against compression

Push up against the timing device to get an indication of end float of the timing device bushing wear (ideally needs to be done with DTI / clock gauge and an absence of the IP on the other end but with other parts still attached wear is usually detectable to an extent that shows "some thing needs to be done about that")

If you are really nervous about pistons hitting valves remove the rocker arms and valve rockers. You can then spin and spin and spin in the safety that you know nothing will be bashing into piston tops.

Don't forget about the A-B timing light situation on the IP. You can replicate the effect of this special tool by feeling for the notch inside the turbo MW IP with a DTI / clock gauge

[rp930]

Thanks Army, I will remove glows, replace upper guide pin, remove rockers. Do I need to replace chain locking screw #94, before turning crank. I still have vacuum pump off, I need to torque cam sprocket and timing device. Do I need Threadlock on these bolts.

When I initially checked end play in Timing Device it was 0.019 of an inch, but the MB spec is 0.002 to 0.004 of an inch, that is a very close tolerance. So I installed a new bushing. I will check again after it is torqued down.

My vacuum pump housing had a crack in it, bearing was still there but it was rough rolling. I replaced it with the same you did in "More than you ever want to know about a vacuum pump" thread.

[Stretch]

Originally Posted by rp930

Thanks Army, I will remove glows, replace upper guide pin, remove rockers. Do I need to replace chain locking screw #94, before turning crank. I still have vacuum pump off, I need to torque cam sprocket and timing device. Do I need Threadlock on these bolts.

When I initially checked end play in Timing Device it was 0.019 of an inch, but the MB spec is 0.002 to 0.004 of an inch, that is a very close tolerance. So I installed a new bushing. I will check again after it is torqued down.

My vacuum pump housing had a crack in it, bearing was still there but it was rough rolling. I replaced it with the same you did in "More than you ever want to know about a vacuum pump" thread.

Sorry I haven't done this job for a while so I'm a bit lost with part #94 you describe - is that a reference to a locking device on the IP? Whatever - if you've used some sort of locking device to hold parts in position then you do indeed need to remove it before turning anything (I guess that's obvious though?)


The picture of your vacuum pump casing does not look like it will last much longer I hope you're not going to refit it. Even though the spring in the piston pump is pushing away from the engine - and hopefully if it fails it will push the vacuum pump away from the timing chain - I wouldn't want to take the risk...


...don't forget when fitting a (replacement?) vacuum pump that the gasket is a cruical spacer between the block and the pump - with out the correct gasket there could be clashing trouble between piston and casing (which might cause cracks?)


If you need to check the FSM I've put in some handy links in this thread =>


Mercedes Startek have done the right thing - to help you do the right thing!


that direct you to the startek (free to access) FSM PDFs by-passing the temperaMENTAL flash player index

[rp930]

Purchased a used Vacuum Pump off Ebay, used my internals as were good except bearings. New bearings, and new block gasket.

I torqued cam sprocket and timing device, installed upper guide pin, and chain locking screw. Removed glows and rotated engine by hand, no interference, I'm going to recheck timing chain (2mm method) now that I think I can find TDC.

The oil pump parts are on their way from Germany, so I'll have to wait.

Thanks for the Startek, but I have a copy thats on a website, if you need it, just send me your email

[hercules]

Mercedes said it was ok to rotate engine backwards when checking valve timing
and pump timing,must reverse at least 20 degrees to be sure all chain slack is removed
when moving forward again.You passed timing marks,back up try again.
Have used this method many times.

[hercules]

Now that new chain is in need to ck pump timing. New car pump timing was set at
26 degrees from Mercedes not 24 as book reads,checked a few when new.
Mercedes knew the chain would stretch.
Have set many to this timing.

[rp930]

Thanks Hercules, I haven't rolled new chain in yet. I take a lot of time to do anything. Working alone I have to find a way to hold chain to sprocket, zip ties seems very time consuming. Maybe vice grips.