Timing chain stretch and replacement? - PeachParts Mercedes-Benz Forum

Chaosmosis · #1 03-17-2003, 08:05 AM

What does MB say about timing chain stretch and replacement?

M-B does not provide a spec saying that if the timing chain is stretched X degrees, then the chain needs to be replaced. What M-B discusses is the use of offset woodruff keys to correct the crankshaft and camshaft tiiming because of timing chain stretch.

So many different opinions on this Board regarding this, I wonder
what would be the maximum before replacement is really??

Chaosmosis
'73 MB 450SL

leathermang · #2 03-17-2003, 08:56 AM

All your valve timing is dependant on the length of your chain... your IP timing can be set to compensate for wear.... How much are you willing to live with ...
One clue may be the Number of degrees that the offset key is designed to correct.... maybe they thought you could deduce from that what they considered too much...
Otherwise it is sorta what you are willing to live with... it is a tedious but not hard job to put in a new chain.... and keeps your cam in the right place at the right time....

Replace Timing Chain?? When??

gsxr · #3 03-17-2003, 01:46 PM

Actually Mercedes does specify a chain stretch limit. For the OM60x engine in my car, that limit is 4 degrees, IIRC. I can dig it up in the manual if you want. What engine are you referring to?

Regards,

#4 03-17-2003, 01:54 PM

if u ask anyone at mercedes here in sweden they say that u should replace it when it is starting to be noisy, like ratteling.. =)

gsxr · #5 03-17-2003, 02:20 PM

That is mostly true for gas engines, particularly the V8's I think. If you hear them rattle at startup, they need replacement ASAP. However most of the diesel chains don't make any noise when stretched, but they will reduce power, MPG, and possibly cause smoke or oil consumption. With synthetic oil the diesel (double-row) chains can last a LONG time. The gas chains are single-row, I believe....

#6 03-17-2003, 04:22 PM

once said and i will say it again, DO NOT USE SYNTHETIC OIL in Mercedes!!! someone mentioned that newer than -98 could be using it...

Part Synthetic is the best option, i believe 10w40 depending on climat outside, but it works from -35 to +30...

gsxr · #7 03-17-2003, 04:48 PM

Oh please, let's not go THERE again. Synthetics are fantastic and WILL NOT hurt your engine. The ~98 up models actually REQUIRE use of synthetic or your warranty wil be void. I use Mobil full synthetics in all my engines with fantastic results, meaning measurable improvement on every vehicle with no problems whatsoever.

For more entertaining reading on this same subject, check this out:

Engine Oil Switch

Regards,

#8 03-17-2003, 04:54 PM

Hmm...I always here a rattle one cold start ups. Warm start ups are fine...guess its not the chain.

gsxr · #9 03-17-2003, 05:14 PM

Kyle,

You shouldn't hear any rattle. It would be a good idea to inspect the chain and tensioner. Both are fairly cheap to replace. Your engine requires valve adjustments every 15kmi, so I'd at least check them out at the next valve adjustment!

#10 03-17-2003, 05:26 PM

PLZ post a link THERE MB Writes about it, and tells that Fully Synthetic oils is better for THEIR ENGINES =) i just wanna se that =)

than i belive in u.

#11 03-17-2003, 05:37 PM

The valves were adjusted by a good mechanic, and he didn't say anything. It's been running very good though, and engine was changed 10-30K ago, so I dunno what that is.

gsxr · #12 03-17-2003, 05:52 PM

Well, at least it runs good. A lot of mechanics don't check the timing chain during the valve adjust unless you specifically ask them to. Next time make a point to ask them not only to check it, but to tell you the number of degrees the chain is stretched... it wil always be stretched a little, you need to know how much. 0-3 is fine, 4-5 means you should replace it when convenient, and 6+ means avoid driving the car until it's replaced!

md21722 · #13 03-17-2003, 06:56 PM

Ya'll need to call 1-800-FOR-MERC and request the lastest and greatest "MB Approved Service Products List". Its free and they'll deliver it UPS to your door. The copy I have lists 6-7 approved oils for use with FSS systems - ALL are synthetic, including Mobil 1 15w-50 and 0w-40, Castrol 5w-50, and some other brands only readily available in Europe. The same document says the listed viscosity chart supercedes "ALL" other viscosity charts. It specifies that 229.1, 229.3, 229.5 be used, when they are not available then B3/B4 and as a last resort CH-4 (these are the diesel specs). Now, for older Mercedes is says that conventional oils MAY be used. The lastest edition has a longer list of approved synthetics.

The other issue is that for FSS vehicles before 2000, MB did NOT require synthetic oil for the FSS system. Starting in 2000, they did. So, for some engines the warranty has been extended to 150Kmi. This is particularly important for FSS vehicles 1998-2000.

The extended warranty information may not be applicable to those outside the U.S. The approved service products list MAY be different outside the U.S. as well.

leathermang · #14 03-17-2003, 07:55 PM

Kyle, If you study the chain tensioner setup I think you will find that it might be possible, without anything being wrong, to have a slap at start up, since the difference between the detent which the tensioner has extended to and the place it runs with oil pressure allows a slight amount of movement... it take a couple of revolutions for the oil under pressure to get to the tensioner to take up that slack....

#15 03-17-2003, 08:37 PM

Here is the technical service bulletin for timing chain stretch:
==========================================
Engine - Noise/Runs Rough/Hard Start/No Power

REF. NO. 05/93

TO: ALL MERCEDES-BENZ PASSENGER CAR DEALERS

DATE: November 1995

(supersedes S.I. 05/91, December 1994)

Revision: Engine 606 included.

SUBJECT:
ENGINES 602, 603 AND 606
ENGINE RELATED COMPLAINTS DUE TO STRETCHED TIMING CHAIN

In model 124 equipped with engines 602 and 606; and model 140 equipped with engine 603 built between July 1992 and April 1994, the following complaints may be the result of a stretched timing chain:

Unusual noise from timing chain area

Rough running engine

Hard start

Loss of power

Increase in oil consumption

In order to check basic engine timing, turn the engine slowly (in normal rotation) using the crankshaft pulley bolt until the mark on camshaft sprocket aligns with the mark on the camshaft bearing cap (arrows, Figure 1). The position of the crankshaft will tell if the chain is stretched, i.e. is still within specifications (Figure 2). For engine 606, refer to SMS Job No. AR 05.20-6010 HA.

1. If the timing mark on the crankshaft pulley is off by 3 °- 10 °:

The timing chain is stretched and should be replaced (Engine 602/603 SMS, Job No. 05.10-320; Engine 606 SMS, Job No. AR05.10-7601 HA).
Visually inspect timing chain sprocket for wear or damage:
Turn the engine 2 complete revolutions (in normal rotation) using the crankshaft pulley bolt and inspect the camshaft sprocket (B, Figure 3 [undamaged tooth]). If the teeth are worn (A) or broken (C) the camshaft sprocket and injection pump timing sprocket must be replaced (Engine 602/603 SMS, Job No. 07.1-240) or (Engine 606 SMS, Job 07.1-8014) along with the timing chain.

2. If the timing mark on the crankshaft pulley is off by greater than 10 degrees:
Inspect the top of the pistons with a borescope to determine if any of the pistons have come in contact with the valves.

If there was any valve to piston contact, the engine must be repaired accordingly.

If the tops of the pistons do not show any visible damage caused by valve contact proceed with step 1 above.

Note: Timing chain guide wear such as grooves or track marks do not justify the exchange of the chain or the rail.
==========================================

Hope this helps. I use 15W-50 Mobil 1 in my "Black Pearl" and think it is a superior lubricant for a superior automobile!