560 Rumble
 

My 'baby' 87 560SL has about 150K mi. and runs well. Burns a little oil but no smoke and the oil pressure is in the high normal range. The problem is that the engine (which starts immediatly) gives off a deep rumble sound for about one or two (at maximum) seconds. This is truly a rumble. Not a knock or a rattle as you would get with a bad lifter or rod end.

I remember that my 57 Ford had the same problem and it was a bad main bearing. Are 560's prone to this? Can mains be replaced on the 560 without removing the crankshaft. (On Fords you can slide in a new bearing around the shaft assuming the crankshaft isn't too badly damaged).
Sorry to use the 'F' word but it had simlar symptoms'

Appreciate some advice/ thoughts before I start to dismantle things.

Thanks in advance!
Barrie

I can't remember the last time I saw a post here about MB engine bearings being a problem. Seems they just don't ever wear out. Maybe some of our members can suggest other possible things to look for.

I agree and have heard the MB bottom end is pretty tough.

Perhaps the mains arn't the problem.

??????????????

Barrie

If the rumble is from the front area of the engine - check your smog pump - they rust up inside and could rumble when first started.

Thanks for the thoughts so far but ....

timing chain isn't that old and the noise only lasts for one second so its hard to tell the location.
Its almost as if it rummbles only until the oil pressure comes up (about one second)
Thats why I thought it might be worn main bearings or possibly a smark knock on start up.

Any thoughts are most appreciated

If your in the cabin with door closed and you hear it, it must be pretty loud. Can you have someone else crank it, while with the hood up you listen to make sure its not the tensioner or chain hitting the rails. Doubt you would hear the crank noise, but it could be a power steering pump needing a fresh fill?

You said it only does it when its cold start for only a few seconds? What weight/type oil do you use? Try and listen with someone else starting it up.

K

Thanks K
PS Pump is OK and I use 20/50 weight oil.

Once again the rumble only lasts for about one second and its a 'solid' rumble.

Barrie

Depending on what part of the country your in, the oil if min base may be to heavy. Your owners manual list 10W-40, 10W-50, and 15W-40. I use Amsoil 15W-40 myself which has great clinging power, and I'm in a very hot part of the country. I only mention this as my experience years ago was with a 20W-50 mineral base oil in my car, which in New England I had to quickly change. Thats just my take on the oil issue. Listening with the hood up, still the easiest bet,,while another cranks her up. Keep us posted.

K

Problem Solved!!!

After almost giving up I heard that my problem might be the timing chain tensioner. The chain, guides and tensioner were replaced about 40,000 miles ago so I thought they should be fine.
To be on the safe side, I removed the valve cover and checked for a sloppy timing chain after the car had sat for 24 hours. The chain seemed tight.
To make a long story short, I replaced the tensioner and all is well.
This still amazes me since even without hydraulic pressure, the spring located in the tensioner seems to exert pleanty of pressure upon the chain.
Has anyone any ideas as to what happened here?
Like I say, all is well but know I'm wondering exactly what happened.

Barrie

Barrie

This only supports what others have attacked me for in the past, on the issue of tensioners. One of the oldest and reliable independents here in town that does lots and lots and lots of these timing chain jobs year in and year out, told me they only use original tensioners from the dealer on this part only. Seems that had several problems over the years with other brands not holding up as seems to be the case with yours. Glad to hear its O.K. Did you keep the part(tensioner) as I would be curious as to know the name on it?

Keith

The old one was a MB original part Keith. I heard the same as you did and installed a new one I got from Mercedes.

Thanks
barrie

Barrie

You said the chain guides and tensioner were changed forty thousand miles ago. Does your engine compartment on the original parts have like a light brownish protectent sprayed on them. Such was the case with the old tensioner that was removed when I did the timing chain job. The new MB tensioner is shinney and aluminum colored looking. Not sure what you call that stuff from the factory, but I guess it is some kind of protectent? At least in mine it is how about your engine compartment. Not on everything of course only seems to be on certain parts. Guess my bottom line question is did an original MB tensioner fail after 40000 miles (provided it was changed) as you indicated. Just very curious.
Regards
Keith D

The chain, tensioner and guides were replaced at about 115K miles with original MB parts. The tensioner I just replaced was an actual MB part and was sort of shiny.

Barrie

Did you do the work yourself? If so, how long does it take.

I've done them on Acura, but not MBZ.

I have a 87 560 SEL with 156K. Not sure when the previous owner replaced them.

I havn't done the chain and guides myself, just the tensioner.
Its a simple job to do. Took about 20 minutes.

Barrie