1984 500 sel timing chain ?? - PeachParts Mercedes-Benz Forum

benz831 · #1 07-26-2007, 08:07 PM

Hi all, I am hoping that someone can point me in the right direction here, I will contact my mechanic tomorrow, but am on pins and needles right now, hoping someone can shed some light on this,
I am driving to work about a month ago and the car dies, I have had this car 6 mos now, never has even sputtered ran beautiful, it felt like the fuel pump went out, I pull the car off the road, bang on the fuel pump, try and start it and get nothing but cranking sounds like no gas or spark, I have it towed to my benz mechanic, expecting a fuel pump, get a call, bad news, timing chain has broke and timing chain cover is broken, motor trashed. I have the car towed home, sick to death over it.
Today I get the courage to go out and pull a valve cover off and see if the valves are really all bent up. to my surprise, there is the timing chain, intact, pull the other valve cover, chain, intact, now I am excited, pull the gas lines off, crank the motor, gas everywhere so fuel pump working, pull the dist cap, crank the motor, rotor turns, still not starting tho, pour a little gas in the throat of the injector throttle, nothing , so I am suspecting there is no spark, am i missing someting obvious, or is my mechanic wrong and the timing chain is not the problem??
Please help

Larry Delor · #2 07-26-2007, 09:23 PM

You say that the mechanic said the timing cover is broken - is it?

benz831 · #3 07-26-2007, 09:26 PM

I looked as hard as I could with my flashlight, I couldn't even see the timing cover, but doesn't the rotor and the fact that the chain is present on both cams show that the chain isn't broken ? the rotor turns, I am ignorant when it comes to this motor, I have always had either diesels or overhead cam 6 cyls,

benz831 · #4 07-26-2007, 09:58 PM

I just got off the phone with a friend, I guess the tensioner might be broke and the chain and the motor trashed and still can see the chain on top, won't be able to tell unless I pull the valve cover and watch what turns when I crank the motor, got excited over nothing probably, it probably is a trashed motor at this point, I do have a 280 motor here that I might be able to throw in it

Hatterasguy · #5 07-26-2007, 10:05 PM

Pull the valve covers and take a look. If you do a search you will find out that one side tend to fails first on these motors. I think its the drivers but I may be wrong. I'd start with that side, may not have to pull both...

benz831 · #6 07-26-2007, 10:12 PM

well , have pulled the valve covers off enough to see that the chain is still on , but I guess if the tensioner is bad, it wouldn't matter much if the chain is intact at the top, I just expected to see no chain present

Larry Delor · #7 07-26-2007, 10:34 PM

What usually happens, is that a chain rail (plastic guide - see pic in partsshop/fastlane) gets brittle with age, and breaks (especially if there is chain slap). The little plastic pieces get inbetween the gear and chain, and mess everything up.

Hatterasguy · #8 07-26-2007, 10:47 PM

Usualy if they fail at speed the cam gear blows through the valve cover....

cdplayer · #9 07-26-2007, 11:11 PM

Quote:

Originally Posted by benz831

Hi all, I am hoping that someone can point me in the right direction here, I will contact my mechanic tomorrow, but am on pins and needles right now, hoping someone can shed some light on this,
I am driving to work about a month ago and the car dies, I have had this car 6 mos now, never has even sputtered ran beautiful, it felt like the fuel pump went out, I pull the car off the road, bang on the fuel pump, try and start it and get nothing but cranking sounds like no gas or spark, I have it towed to my benz mechanic, expecting a fuel pump, get a call, bad news, timing chain has broke and timing chain cover is broken, motor trashed. I have the car towed home, sick to death over it.
Today I get the courage to go out and pull a valve cover off and see if the valves are really all bent up. to my surprise, there is the timing chain, intact, pull the other valve cover, chain, intact, now I am excited, pull the gas lines off, crank the motor, gas everywhere so fuel pump working, pull the dist cap, crank the motor, rotor turns, still not starting tho, pour a little gas in the throat of the injector throttle, nothing , so I am suspecting there is no spark, am i missing someting obvious, or is my mechanic wrong and the timing chain is not the problem??
Please help

Do a search on "crank position sensor" if indeed your problem is not the chain...curious to know myself. I have a 500SEC. Probably same engine.
But so far with 235,000 miles, it's still running pretty good

benz831 · #10 07-26-2007, 11:28 PM

well , this just turned 300K , the weekend will tell the story as I am going to try and pull the timing chain cover, will at least turn the motor with the valve covers off and see what if anything turns,

Hatterasguy · #11 07-27-2007, 12:01 AM

Has the chain ever been replaced!? It must have no way the original lasted 300k.

benz831 · #12 07-27-2007, 12:06 AM

I hadn't asked the previous owner, I never knew that the timing chains were an issue until this happened

Hatterasguy · #13 07-27-2007, 12:07 AM

On MB V8's of that vintage they need to be changed about every 10 years or 100k miles. If not they can fail, but usualy on start up.

david s poole · #14 07-27-2007, 10:26 AM

pull off the valve covers and look with a light very carefully at first the left bank.what usually happens is that the chain jumps time and the pistons meet the valves and the valves bend and won't seat[close off] if this has happened you will be able to reach down and remove one or two rockers by hand[without the special tool] this will confirm bent valves and requires a complete top end o/haul and helicoiling of the head bolt holes in the block[36]

benz831 · #15 07-29-2007, 01:29 PM

ok, had the valve covers off today and the pass side looks good,
plastic guide on the driver side broke, and plastic pieces wedged in
cam gear between chain sprocket. removed cam, a few bent valves on pass side,I need to pull the head, and pull the timing case cover, any sequence that you can point me in, greatly appreciated !
I still think I got away cheap, am going to pull the pass cam and do compression check on the other valves as well tho to make sure,
I am looking at replacing chain tensioner, chain, guides and redoing drivers head and valves cam wasn't harmed,