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  #1  
Old 01-27-2014, 02:26 PM
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1977 300d timing chain scoring inside of valve cover?????

Hello and thanks for taking the time to give me your advice.

I was recently given a 1977 300d that had been converted to Biodiesel, and told that it needed a new timing chain.
When I removed the valve cover it looked as if the chain jumped off at some point, scoring the top of the valve cover.
Not a lot, maybe once or twice.

The chain itself doesn't look scored or worn, but could be stretched.
The tensioner, however, is putting NO pressure on the chain and an be depressed all the way down with a screwdriver without much effort.

I was thinking maybe it just needs a new tensioner, but have never done either one of these replacements before.
How do I determine if the chain is bad?
Does the tensioner run off of oil pressure, or can I assume that it is shot.

What would ya'll do?

What about the timing if the chain did jump a link or 2?
How do I make sure that it is reset and what is the best way to do this?
What would ya'll do in this situation?
Thank you for your help!

.


Last edited by whunter; 01-28-2014 at 09:03 PM. Reason: readability
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  #2  
Old 01-27-2014, 05:36 PM
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Posts: 93
Timing chain!

If you decide to replace it here's a new chain and tensioner I have offered for sale:

http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/349903-wts-617-timing-chain-tensioner.html

If you don't know the car's history and the engine has 200,000 miles or more a new chain is cheap insurance against catastrophic failure.

The tensioner uses oil pressure and it has a spring inside of it, the piston ratchets out and should not allow it's piston to be forced back when in place.

There are many threads about chain replacement one recently had some good links mentioned in it about the complete timing chain and guides R&R. It's in the Diesel section. Here's the ones I was reading

Approximate cost timing chain repl 300sd

9 degrees of chain stretch
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  #3  
Old 01-27-2014, 07:31 PM
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Join Date: Aug 2005
Location: Oregon
Posts: 314
This article will give you the basic information for checking the timing chain:
PeachPartsWiki: Measuring Timing Chain Stretch

The quick method described will be good enough to tell whether or not the chain has jumped. If the engine is able to run, then you probably haven't lost the timing yet. Valve damage can occur with a cam that is off by a single tooth. The dial indicator method is far more accurate for determining the extent of the chain stretch.

The tensioner in your engine is probably the old style. It should extend fully, and will compress when sufficient (considerable) force is applied to the piston. It is operated by a combination of an internal spring and oil pressure. If your tensioner rail has been flapping, then there's a good chance that it may be damaged as well. If you need to replace the chain, then it is worth considering replacing the other guide rails as well.
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  #4  
Old 01-27-2014, 08:24 PM
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Answer

Quote:
Originally Posted by gocarnivore View Post
Hello and thanks for taking the time to give me your advice. I was recently given a 1977 300d that had been converted to Biodiesel, and told that it needed a new timing chain. When I removed the valve cover it looked as if the chain jumped off at some point, scoring the top of the valve cover. Not a lot, maybe once or twice. The chain itself doesn't look scored or worn, but could be stretched. The tensioner, however, is putting NO pressure on the chain and an be depressed all the way down with a screwdriver without much effort. I was thinking maybe it just needs a new tensioner, but have never done either one of these replacements before. How do I determine if the chain is bad? Does the tensioner run off of oil pressure, or can I assume that it is shot. What would ya'll do? what about the timing if the chain did jump a link or 2? How do I make sure that it is reset and what is the best way to do this? What would ya'll do in this situation? Thank you for your help!
Replace the tensioner, it is damaged.

I suggest you "ROLL" in a new timing chain.
Diesel Timing Chain Thread - PeachParts Mercedes ShopForum


Timing chain crimper how to


Valve Cover Gasket
MB# 6170160180
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST

Timing Chain With Master Link (136 Links, Double Row)
MB# 0039976294
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST

Timing Chain Tensioner
MB# 6150500811
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST


Drip Timing Threads

Factory service manual data you may need.

Mercedes-Benz Model 123 - Disc 2

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-215.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-310.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-320.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-330.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-340.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-440.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-412.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-410.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-240.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-235.pdf

Mercedes-Benz Model 123 - Disc 2


http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-210.pdf

.
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  #5  
Old 01-28-2014, 09:32 AM
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I would agree, it sounds like a new chain and tensioner are in order, as mentioned , if there are a lot of miles on the car - as they say - Just do it. Problem is , if you have it done it can be $$$ , so you have to examine money spent and the value of the car your future with the car
It can be done in the driveway , but it is not for the faint of heart. Good luck
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  #6  
Old 01-28-2014, 08:50 PM
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Thanks everyone, I would def. Roll a new chain on if i knew that it hadn't jumped, but I'm assuming that it has since it hit the top of the Valve cover>LEFT COAST- by quick method do you mean lining up the marks and look for 2deg to determine?
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  #7  
Old 01-28-2014, 09:10 PM
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Answer

Quote:
Originally Posted by gocarnivore View Post
Thanks everyone, I would def. Roll a new chain on if i knew that it hadn't jumped, but I'm assuming that it has since it hit the top of the Valve cover>LEFT COAST- by quick method do you mean lining up the marks and look for 2deg to determine?
All of the data you need for checking base MECHANICAL engine timing is in the following links.

Factory service manual.

Mercedes-Benz Model 123 - Disc 2

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-215.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-310.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-320.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-330.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-340.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-440.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-412.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-410.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-240.pdf

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-235.pdf

Mercedes-Benz Model 123 - Disc 2


http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-210.pdf

################################

Replace the tensioner, it is damaged.

I suggest you "ROLL" in a new timing chain.
Diesel Timing Chain Thread - PeachParts Mercedes ShopForum

Timing chain crimper how to

Valve Cover Gasket
MB# 6170160180
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST

Timing Chain With Master Link (136 Links, Double Row)
MB# 0039976294
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST

Timing Chain Tensioner
MB# 6150500811
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST

Drip Timing Threads

.
__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/
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  #8  
Old 01-28-2014, 10:51 PM
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Join Date: Aug 2005
Location: Oregon
Posts: 314
Just line up the marks at the cam sprocket and tower. Get them as close to perfect as you can. Read the timing on the crankshaft balancer. It will read close to 20° if you are off a tooth. This is not very likely, but if it is the case, then you'd probably be better off not wasting any more time on this engine unless the car is otherwise a good example.

If the reading is anywhere close to 0T, then the chain has not jumped. Having run with a bad tensioner, I'd agree that it would be best to roll in a new chain and replace the tensioner, but I'd strongly recommend taking a good look at the rail. These get pretty beat up when the rail is just slapping around, especially the part that contacts the tensioner piston. The pivot, where the rail is pinned to the block will also develop exessive play if the tension is loose for an extended period. While you have everything apart to get to the tensioner is the best time to replace anything that needs replacing (thermostat, bypass hose, etc.) and would require the same effort just to access the parts.
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  #9  
Old 02-05-2014, 01:01 PM
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ok Great thanks for the help everyone!

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