1984 500 SEL - Timing chain questions - HELP
 

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

timing
 

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

cheap insurance
 

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

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?

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

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

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.

pdf
 

It is on its way
m

tensioner
 

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

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

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

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

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

parts
 

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

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.

Hello friends,

Thank You again for all Your really good help and all the advices. I cant thank You enough and I really appreciate it.

I ordered new rails, a tensioner and a new chain earlier today. The rails were cheap but the chain was about 120 USD and the tensioner about 190 USD. Probably because the sales tax here in Sweden is 25%. Anyway, I thought it probably be well spent money if it cures my car.

Some of the stuff needs to be sent after from Germany so I probably have to wait until this weekend before I can get busy with the fixes.

I´m thinking of borowing a fiberoptic setup the have a look through the spark plug holes at the pistons for any signs of contact between the valves and the pistons. It probably works great as well to see when the number 1 piston is at TDC so that I can determine if the harmonic damper is out of alignment.

One thing that I wanted to ask about is if there is any good way of checking if the tensioner is OK or not? The reason is ofcourse if I should try to save the 190 USD.´Also I would like to ask how this Mercedes tensioner works. All the other tensioners that I have seen, be they mechanical or hydraulical, they only elongate and never retract. But when I rotated this engine by hand I could clearly see that when i started to put load the wrench the tensioner elongated with about 1 1/2 inch and when I released the pressure it retracted by the same amount. I might be completely wrong here but wouldn´t that mean that everytime You start the car, and until the oil pressure builds, You would have a lot of slack causing the chain to slap the rails?

Well, I guess that was all for now. I´ll let You all know how it goes with my replacement and the fiberoptic inspection.

Thanks again,

Mikael

Tensioner
 

Michael Your tensioner is bad. The tensioner should hold pressure so you do not have slack when you start the car. The fact that there is slack could be what has caused your problem to start with. The clattering sound on startup is the first sign you need a new tensioner. By the way those prices are high a new febi tensioner is @us$60 and a chain is US$80
Good luck this weekend.
m

Hello again Friends,

Let me tell You that standing outside when its below freezing, snow is falling and wind is blowing, changing cam chain tensioner and all the rails, is not what I would recomend as recreational fun. Anyway, most of it is behind me now.

I changed all the parts and following the hints and help I got from the list earlier it was no big deal except for some fasteners that was rather stuck. I also checked that the crank timing was at 0 degrees when No 1 cylinder was at TDC to eliminate that possibility of error. Also I found that 2 of the rails were broken instead of 1 as I wrote earlier.

Finally when I got it together enough, I rechecked the timing between the crank and the cams. Now the 2 timing marks on LH and RH cam align exactly at the same time but the crank is still at 14 - 15 degrees.

My assumption from this is that I should change the timing of the cams by 1 tooth which would give me a timing change of 20 degrees between the cams and the crank (there is 36 teeths on each cam i.e 10 degrees betweeb each. The difference of 5 degrees is probably because the chain is not so much stretched when I rotate it by hand as it will be when the engine is running.

Now this is me guessing and I was hoping for input from all of You if my guesswork is correct or not.

As soon as I have Your input, I hope that my next tread will be that of a smooth running engine and no tapping noise. I will ofcourse run a compression check as soon as i got the covers on but I´m waiting with that until I´m sure that I got everything timed and togheter.

Many, many thanks to all of You.

Mikael Westerberg
1984 500 SEL
Vanersborg, Sweden

To get everything to line up, the chain needs to have its slack on the right side where it would be taken up by the tensioner if the engine was running. It needs to be tight between the right and left sprockets.

If you have everything positioned like this and you are still off, then try repositioning the sprockets to get the marks to line up. Turn the engine over a couple of turn by hand to verify that you are not having any piston-valve contact.

Then crank the engine for a few seconds with the coil wire unplugged. You should build up oil pressure in the tensioner, and the chain will tighten. Do one final check of the cam marks - you should be dead/spot/right on at TDC and good to go.

Chain rails
 

Mikael

I thought I was lucky. changed the chain rails last weekend, not too hard a job if you follow the procedure from the link you have been given, the only thing I would add to the procedure is a 6mm bottom tap for cleaning the threads out in the pivot pins, before you insert the puller, I made a small slide hammer which made the job a bit quicker. I also had two broken chain guides and the bits no where to be seen, chain stretch is about 10 degrees with the new guides ( not 28 like yours ) but will be changing the chain and tensioner anyway, my car (500se) has done very similar mileage to yours and I also needed to change the valve stem seals, this can also be done with very little expense and without taking the heads off, I’m actually looking forward to doing the chain job, the thought of a six foot long chain emerging from the depths of the timing case while the new one is being fed in really tickle’s my fancy ( I’m a mechanical nut )

Good luck

Hi again,

I now have everything back togheter. New cam chain, new chain tensioner and new rails. As I wrote earlier the new parts took me back from 27 - 28 degrees of stretch/ wear to about 15. Following the advices I also changed the timing by one tooth putting the timing on 5 degrees before TDC and with some cranking to pressurize the tensioner I was at 2 -3 degrees before TDC.

Now, I did double and triple check the timing marks everywere but when I started the car the noise was terrible and it was running very poorly. Took it apart again and changed one tooth back and voila now it is running like before.

I dont think anything was damaged because of the one tooth change and I have been running the car today. The slight stumble at idle seem to be somewhat better and the performance is noticeably better. I still have the tapping noise but I´m not terrified by anymore as I were when i saw the 27 - 28 degree stretch the first time.

Now the strange thing about all this is that for some reason the timing marks on the cams cant be right - can it? I did check that the crank timing was at 0 degrees when the No1 cylinder were at TDC. And with everything lined up according to the advices the car did hardly run.

My assumtions is that the timing marks on the cam must be off for some reason. I haven´t yet made the compression check to see if something was damaged in the process but will do so. I also think I read somewere that the no1 intake valve should start to open 12 degrees after TDC which should be quite easy to check.

Any thought on this?

Best regards,

Mikael

To be sure of the basics:

- The notches on the thrust washers lined up with the marks on the cam towers.

- The little "0|0" mark on the balancer under the pointer.

- The chain tensioned fully, no slack between the sprockets.

Under these conditions, mine lined up perfectly with the new chain.

Are you sure the Woodruff keys have no offset?
 

Mikaelw - when you had the cam gears removed, did you check that the Woodruff keys which locate in the slot on the cam shaft and on the gear wheel are straight?

MB sells them in various offsets up to 10 degrees and it's possible a previous owner/mechanic compensated for bad timing by installing offset keys. Offset can be positive or negative, depending how you install these.

With a new chain and tensioner, you should be using straight keys on both cams, not dog-legged ones. Offset keys would continue to return a timing error.

Hi again,

Here´s the things that I checked after I had the new parts installed:

1) Cam alignment: Both cams align very nicely with their respective marks on the thrust washer. There is no visual difference between when they align but they both align at the same time.

2) Crank alignment: I checked that the timing mark on the crank (harmonic damper) shows O when when the No1 piston is at TDC.

3) New tensioner was installed and I cranked the engine for about 5 seconds to pressurize it.

4) As far as I could see the Woodruff keys were straight (I did not remove them for inspection but looked at them in place and there was nothing suggesting that they were of the offset type.

At this point I did check the crank to cam alignment and when the cams aligned with their respective tower the crank was at 2-3 degrees before TDC. I had rotated the engine by hand several times to make sure that there were no contact between the valves and the pistons.

I thought everything looked fine and put the rocker covers etc back on and fired the engine up. There was a terrible noise as if I ran a couple of valves in the pistons and the engine was running very poorly.

At this point I realized that things were not quite OK so I took the rocker covers of and moved back the cams one tooth each. This were how everything lined up after I changed the tensioner, rails and the chain. At this point the crank (harmonic damper) showed 15 degrees after TDC when the cams were aligned with the marks on the tower. My fear at this moment was that I damaged some valves but thoght that I now was in the middle of how the car was before I took it apart and how it was moments before when I started it.

Therefore I put the rocker covers and all other parts back on
and started it up. It now ran as it did before I changed all the parts. I drove it to work yesterday and today and it runs slightly better than before. The idle is still a bit uneven at times and the response is noticeably better (not sigificatly better). I still have the tapping/ knocking noise which doesnt get better or worse at different rpms or load conditions. If I run the engine and pull one by one of the ignition cables off there is no change to the tapping. This makes me think that one of the hydraulic elements need replacement

My conclusion is that it must be something wrong with the timing marks on the cams or everything should have been fine the first time I started the car up after the parts replacement. I don´t know if that is possible or if there is something in the process that I overlooked.

This is why I wonder at what number of crank degrees the intake valve should start to open. If I understood the valve timing procedure correctly the degrees should be checked at 2 mm of intake valve lift but I´m not sure what the reading of the crank should be?

Or is there a smarter way of confirming if the cam timing marks are correct.

Any and all hints are appreciated.

Thanks/ Mikael

Michael,
i sent you the pdf for checking the valve openings and timing information. I would check make sure those match up with your engin and specific cams.
m

OK, I realize that this suggestion is far-fetched, but Mikael's last report has bothered me and I am really stretching for a reasonable explanation.

Assuming that there are no offset keys in the cam(s).

All I can come up with is that the distributor drive gear may be off a tooth. This is the gear right below the left cylinder head. When it is installed, or the chain changed, it needs to be lined up to a mark in the crankcase. This is to allow the distributor to be set relative to #1 TDC. With the cams correctly set relative to TDC, which was a CHANGE from the way it was before, the ignition timing was changed relative to the valve opening and started firing with either the exhaust or intake valve open when the car was started.

The result is a lot of noise and a poorly running engine. Mikael sets the cam timing back and thus restores the ignition timing relative to the valves which makes the engine run better. By some miracle, in the current position, the valves are not hitting the pistons.

I am not suggesting that you pull the front cover off to check this, but take a look at where the firing point is with the cams and crank in closest agreement - the way you had it before.

All I can think of other than some wierdness like a wrong part somewhere in the valve train.

Offered almost apologetically.

Hi Martin & Chuck,

I really appreciate Your help. If You ever come to Sweden, by all means, look me up and let me buy You a cold one and start the barbecue for with a couple of nice T-bones on it.

The only reason why I did not check the valve timing as per the spec´s that Martin provided me is that I don´t have the valve adjusting screw No# 116 050 11 20 and I didn´t think I would get correct readings doing the check without that. I kind of hoped that by miracle there would be an easy check for me with the available tools.

Anyway, since I suspect that one of the hydraulic compensators is damaged but haven´t found which one yet(causing my tapping noise, I guess I better bite the bullet and head down to the dealer tomorrow and buy the valve adjusting screw to be able to check the timing properly and get some leads on this.

I´ll get back again as soon as I have had a good chance to look at this.

Please remember - if ever in Sweden!!

Thanks again/ Mikael

Tapping Noise
 

Mikael

Did you manage to cure the tapping noise and if so how did you track down the offending hydraulic unit. I still have the same problem after replacing the chain, guides, tensioner and many attempts at isolating the hydraulic unit thats making the din.

Hi Hoggy,

I´m afraid i didn´t track down the tapping noise origin yet. After I changed the tensioner and the rails and the chain the noise was still the same. I´m waiting for spring time to set in at the moment so that its more comfortable to work outside. Once it´s warm outside I will take my Jag out and spend some time with finding the source of the noise. I have been listening a lot with my stetoscope and I´m pretty sure that the noise comes from one of the 4 front hydraulic compensators on the passenger side cylinder bank.

I´ll get back with more info.

Cheers/ Mikael

Tappet Noise
 

I finally tracked down the noise on my car, not good news, I made a partial valve cover so I could run the engine and isolate the valve set making the noise. You need this as the engine pumps an amazing amount of oil to the heads and this ends up all over the floor. The valve set in question is number 1 exhaust but could not stop the noise no matter what I did, I eventually removed the rocker arm and the valve springs and pushed a piece of hose over the valve stem so that I could lift it up and down and found that the noise is coming from the valve making contact with the valve seat. This could mean two things
1. The exhaust valve is slightly bent.
2. I think the most likely – The valve seat is loose in the head.

So I’m in for a heads off job to rectify it, not really looking forward to that and it looks like I will have to purchase some special tools to do the job. I have been through the hydraulic lifters a good number of times now, so if you have a problem with them let us :(

Hi Bob,

Shouldn´t it be fairly easy to check if You had a bent valve or a loose valve seat by doing a compression check?

Thinking about it I better do one myself (once i get some time for it because I have an 70 Year old wooden sail boat as well).

Good luck/ Mikael