560SEL wisdom needed
 

Hi everyone,

I bought an '89 560SEL (my first M-B) in September and have been using it rather heavily (I've put 8,000 miles on it since), and enjoying it tremendously. It does have a few nagging problems, though, and I'd greatly appreciate any/all tips before I tackle any of these problems with my hands and/or wallet....

1) The driver's side door doesn't trigger the courtesy lights and alarm; the other doors do. A search through previous posts on this site revealed that this may be a relay problem -- can someone please elaborate, since I'm a little illiterate when it comes to M-B electonics? Is this a DIY fix? What do I need to do?

2) The AUTO setting on my A/C unit works only intermittently; the slow and fast fan settings work fine (except for one morning, when none of the buttons worked). The car also makes long "sniffing" sounding noises when the A/C is on (especially if the car shifts its weight, as during braking or acceleration), and there are occasional popping sounds coming from somewhere in the front as well. Are these noises normal? What's the most common cause for the AUTO setting malfunction (other than a faulty button, which I doubt)?

Speaking of bezerk electronics, I've had one episode in which my A/C unit shut off completely, and, at the same time, my turn signals didn't function either. Then after a few minutes the air suddenly came back on and the turn signals started working again, too. Another time, at night, all the lighted buttons on my A/C unit went dark (but it kept blowing air, and all the other buttons stayed lit). It stayed like that until I stopped for gas; when I turned the engine back on, the lights were back, too. Could there be some common cause for all this weirdness? Bad fuses? Bad relay?

3) The car idles rough for about 5 seconds after start-up, usually when it's cold outside, then runs fine. Is this usually a dirty injector? Can I just add some STP Fuel System Cleaner, or do I need to have this professionally taken care of?

4) Most annoying: car starts vibrating around 70mph, then gets variably better or worse as I increase speed; the severity of the vibration and whether it gets better or stronger with speed varies randomly. Balancing (by two different shops), alignment, and tire rotation didn't help. There's also some balding on the outside of the left front tire. The left outer tie rod was recently replaced, without any benefit. The right control arm was replaced a few years ago. I know numerous other owners have had problems like this, and often they can't find the source of the problem -- having said that, though, what should I have checked/replaced before I give up?

5) The car has 136k miles on it, and I guess that means it's due for a guide rail replacement. I understand that the guide rails can break and the plastic debris as well as the off-track timing chain slapping around the engine bay can cause lots of damage. What I'm not clear on is this: do the rails break because they are old and brittle, or do they break if/when the pretensioner dies and the chain gets slack (and slaps against the rails with more force than usual on start-up)? IOW, am I better off replacing the rails, or the pretensioner, or both?

I realize this was a really long post -- thanks in advance for reading this far and taking the time to share your knowledge with me. I look forward to your replies!

Can't really help with #1. I would suspect the switch in the frame of the door.

#2 - the beserk electronics sounds like a flaky ignition switch. Encountered the same thing on a 560SL that I was test-driving before I bought mine. For the AUTO setting, there's a cabin temperature sensor. Don't know where it is on the SEL, but for the SL, you get to it by removing the glovebox. There's a foam tube that eventually disintegrates and needs to be replaced. I would suspect it's the same for the SEL.

#3 - I would probably start with the cold start valve or coolant temp sensor, but it really could be any number of things. I've been chasing idle problems on my M103, but not the M117.

#4 - Possibly tread seperation on the tires. If one is bald, then get new tires. Replace them in either pairs, or all four at once.

#5 - If they haven't been replaced yet, you're living on borrowed time. Replace the chain, tensioner and guide rails. $700-$800 every 100k miles shouldn't hurt too bad. Or, since it's labor intensive, you could change them yourself and save a bundle. Probably not more than $150 in parts.

This site seems to have very reasonable prices on Mercedes parts:

http://www.oem-mercedes-benz-parts.com/mercedes_benz.htm

here is the info on the site about the timing chain for a 86-91 560SEL-
PART NUMBER SEARCH RESULTS WITH PRICES

Vehicle 1989 Mercedes Benz 560SEL
Part: Timing Chain

Note: 198 link




Product Brand Availability Retail Our Price

A5100-11944 Timing Chain Iwis IN STOCK $107.00 $67.90

Hope this helps somewhat.

4) Most annoying: car starts vibrating around 70mph, then gets variably better or worse as I increase speed; the severity of the vibration and whether it gets better or stronger with speed varies randomly. Balancing (by two different shops), alignment, and tire rotation didn't help. There's also some balding on the outside of the left front tire.

Newbie here. Like to say hello to every one.

I am having this same problem. If any one has a clue as to what is going on here please let me know. The car does not pull, drives straight, seems to float a fair bit though.

On the vibrations...My 85 had/has it. I replaced motor mounts and the vibes moved to above 80mph..a range I could live with.....well yesterday the vibes came back at 70~75mph.

I am going to put the rear up on jacks and drive the car (rear wheels free wheeling)...if no vibes then I will rule out flex discs, driveshaft support, trans and diff mounts.
My front end pieces were given the okay by an indy but if the vibes persist, I think all new rubber in a 21 year old car isn't unreasonable.

I have also heard the rear subframe mounts can cause this but have no layman's method of checking them.

Pls. post all success stories for us in the suffering.

Don

Janos:
Here are some pointers based on my experience with my 91 560SEL:
1. Driver's side door - your door switch is probably stuck to open position (it thinks the door is still closed?)
2. AC - I have no input on this..
3. Rough Idle - I would make sure that the electrical stuff is in good shape ( ie distributor cap and rotor, plugs, plug wires, etc). Then I would look at the fuel delivery ( EHA test, duty cycle test, idle control valve, temp sensor, throotle position switch...a lot of posts on these procedures). I once had a rough idle problem for a long time... I adjusted the idle at the tower as it was running lean, and replaced the idle control valve. I also found one plug to be improperly installed...
4. Vibration at about 70MPH - similar problem I had ..resolved problem by replacing motor mounts...the motor mounts on my car was badly wornout..
5. Guide rails - this is an expensive repair if they break and cause other things to break inside the engine. I replaced the upper guides and tensioner on my car about a year ago. The guides were discolored and slightly worn-out ( slight chain tracks were visible). The tensioner was badly worn-out. The metal backing was already almost exposed..

hoep tis helps..

If the front end is good (ball joints, tie rods, drag link...) it is probably bad tires, a bent rim or tires out of balance. I changed almost ll the body rubber including lower a-arm bushings and I didn't have any vibration before I changed them. I also changed the rear sub-frame bushings and differential busing and it helped wander, but no vibration. I have a car that had a bent rim and it showed up after chasing vibration. You can balance a square but if it's not concentric it will set op a vibration. MHO...

Regarding idle, I changed almost the whole ignition system but the big change to idle was changing all the fuel injectors. It was my last resort. A vacuum leak will cause problems there too.