1984 500 SEL - Timing chain questions - HELP - PeachParts Mercedes-Benz Forum

mikaelw2001 · #1 01-25-2003, 10:09 AM

Hello Mercedes frinds,

As I mentioned in my earlier postings my car have developed a tapping noise lately. It´s not really bad but more like excessive valve clearance on one valve. Fellow listers suggested that I do the "Fuchs finger test" which I did today. Almost no play at all on the hydraulic compensators.

Now to my problem. I also opted for checking the timing chain stretch based. I aligned the timing marks on the cam/ tower and took a reading on the crank - IT WAS 28 DEGREES !!!

I´m wondering if I did something wrong when doing this check? I just took the right (passenger side) rocker cover off. The spark plugs are still in. I rotated the engine clockwise (standing in front of the car/ facing the engine). I also noticed that the chain tensioner is moving quite a bit when rotating the engine.

The car has been running fairly fine since I bought it some months ago except for a slightly stumble at idle. From what I have read on this list the reading should be no more that 4 degrees.

Am I just lucky that the engine is still alive??

Please give me input on what to do. I´m quite nervous now.

Many thanks,

Mikael Westerberg
1984 500 SEL
Vanersborg, Sweden

mhingram · #2 01-25-2003, 10:39 AM

Michael,
I have the pdf info from the manual but need to send it to you please email where you want me to send it to.
m

#3 01-25-2003, 10:46 AM

if you haven't put a new chain in yet i would go for it. it sounds like time to do it. you may be very lucky ur engine is still alive. it has happed to me with a 380se. the guide was already broken when i took it into the shop. the Tech said its not often people get that lucky! dish out for the chain, you wont be sorry.

Scott

ctaylor738 · #4 01-25-2003, 11:21 AM

That is a huge amount to be off. Assume that you aligned the notch on the thrust washer with the mark on the tower. I would not tempt fate by starting the engine in this situation.

What do the tensioner rail cover and slide rail look like?

mhingram · #5 01-25-2003, 12:31 PM

This can be within 1 degree of dormal depending on the engine type.
so please review the manual before doing anything.
m

mikaelw2001 · #6 01-25-2003, 12:41 PM

It seems I´m in for a new chain and rails.

mhingram please, please mail me the pdf-files on mikael.westerberg@telia.com. I would really appreciate it since its quite obvious that I need it.

From what I could see the rails looked fine but I guess will look more closely on this tomorrow.

Ctaylor, I´m not sure if I know what You mean with the tensioner rail cover. Could You describe it to me?

You guy´s are great and the forum is great. I guess it has saved lots and lots of Mercedes from an premature trip to the scrappers.

Thanks again,

Mikael

ctaylor738 · #7 01-25-2003, 01:03 PM

The tensioner presses against a pivoting curved rail, which presses against the chain. The rail has a removeable plastic cover that wears as the chain rubs against it. I believe that you can replace it without removing the rail by pushing it toward the bottom of the rail. If it won't come out that way, it is fairly simple to remove the rail at its pivot using a bolt and some washers as a puller.

mhingram · #8 01-25-2003, 02:01 PM

It is on its way
m

mhingram · #9 01-25-2003, 02:24 PM

Michael your chain might be fine but your tensioner should not move much. When you start up the car do you get a short clattering sound near the tensioner usually right front. If you do I would definately recommend a new tensioner. The debate still rages on doing both tensioner and chain at the same time. I will let you make that call.
m

psfred · #10 01-25-2003, 02:50 PM

Mikael:

Make sure you are rotating the engine in the normal direction of rotation (clockwise when facing the engine from the front!) -- the fan blades will give you a clue, too.

If not, you have pulled all the "slop" in the chain out of the short side and the number will be way off -- at 28 degrees, you bend valves!

Also make sure the tensioner rail is tight -- it's the one on the right side below the cam. You can use a large screwdriver to pry it in toward the center of the engine.

If you still have significant stretch, replace the chain, it's fairly easy (and not that expensive to have done, either). This will cure the late valve timing and improve low speed operation considerably.

If the stretch really is 28 degrees, check the compression, you may have already started damaging the valves.

Neglect is a terrible thing -- check chain stretch is one of the MB regular maintenance things a good tech will do every 30,000 or 60,000 miles at the "big service", but no one else every does.

Peter

mikaelw2001 · #11 01-26-2003, 04:51 AM

Hi Again,

I´m on my way out now to check the chain anpther time. I will open up the left (driver side) cover as well just to see were that side is timing wise.

Sometimes I have the start up clatter as well so I will put a new tensioner on the list as well.

After I changed the chain , tensioner, rails I guess I will have to do a compression check as well. I dont think it is much use to do it now when the timing is so far of.

I will get back as soon as I have more info.

Thanks a lot,

Mikael

mikaelw2001 · #12 01-26-2003, 10:01 AM

Hi again friends,

This morning I took of the left (drivers side) rocker cover to check the cam timing as well as the rails on that side. I also rechecked the timing on the right side. Here´s what I found.

-Timing on right side 27 - 28 degrees,
- Timing on left side 21 - 22 degrees.
- On one rail on the left side a piece about 40 mm long and 10 mm wide is missing (1 1/2 inch by 1/2 inch).
-witness marks on all rails but nothing alarming.
- No signs of plastic debris anywhere to be seen.
- No signs of a divideable link on the chain suggesting that the chain is probably the original one.

The odometer suggests that the car has 143 000 Km (about 90K miles on it. Can the original chain really be that much stretched or should I suspect that the odometer has been tampered with?

The rail that was broken is the left one when standing in front of the car on the left cylinder bank.

Now, my conclusions from the inspection and with all the good adwise from You all is that I need to replace the chain, the tensioner and all the upper rails.
I will also do a compression check once I have the parts replaced and the cam timing fairly well adjusted.

I guess that the plastic piece from the broken rail is "down there" somewhere and I dont know how long its been like that.

Should I be worried about this plastic piece and do You know were it "normally" ends up? Is it difficult to get in there? Is there anything else I ought to think of while I´m at it?

Many thanks,

Mikael

psfred · #13 01-26-2003, 10:33 AM

Mikael:

I would suspect that the previous owner/s didn't change the oil frequently.... The chain is SERIOUSLY worn and must be replaced pronto.

However, you do have a very lucky car -- that missing piece is sitting safely in the oil pan, and it DIDN'T go where it usually does -- down between the chain and the sprokets! You have avoided, by the skin of your teeth, the typical broken chain/valve job -- about $4000 if done by a shop!

You need a new rail to replace the broken one and a new chain. The new chain should fix up the rough idle, etc. The noise is the chain slapping because you are out of tensioner travel. You might also want to replace the tensioner just to be safe.

Sadly, I would also recommend doing a compression check -- it is possible the valves on the right side are touching the pistons!

Peter

mhingram · #14 01-26-2003, 02:00 PM

Michael,
You should take the entire oil pan off. You should find your leftover parts down there. Pretty easy just time consuming. Sorry about the bad news. Here is a link about timing chain change that might be useful: http://www.pindelski.com/cars/W126/W126_chain_rails/W126_chain_rails.html
m

pmckechnie · #15 01-26-2003, 04:01 PM

Mikael,

I would also check the harmonic balancer very carefully. I don't think the cams can be off by that much and not bend valves.
The balancer is mounted to its hub with rubber and after 18 years it could have slipped thus giving you a false reading. That in itself is not bad, but now if you set everything up with it off, then you will bend valves the first time you turn the engine. You can look down into the spark plug hole of #1 cylender (or have someone else look for you) as you turn the engine and see if the timing marks are a TDC when the piston is as high as it will go. You can rock the engine back a forth to get as close to TDC as posible. If this is off by more then a few degrees, the harmonic balancer has slipped and will need to be replaced before anything else is done. good luck.
I also have a 84 500 SEL with 250,000 miles and it still runs great.