I haven't been this scared since my oil consumption

[Lexxani]

do you get a metallic whine on startup? I was experiencing that problem when I broke a plastic chain guide in my drivers side head, that may have something to do with that 'wack' sound, if your chain is loose enough on start up to hit your cyl head.

[Roncallo]

Originally Posted by Lexxani

do you get a metallic whine on startup? I was experiencing that problem when I broke a plastic chain guide in my drivers side head, that may have something to do with that 'wack' sound, if your chain is loose enough on start up to hit your cyl head.

I agree this is the first thing that should be checked. In fact before you even start the engine again. When was the last time you rails were replaced. Also did you replace the tensioner rail. The tensioner rail is the only rail that wears out of the 4 that can be replaced from the top. It is often not looked at or replaced because people think its hard. It's not. 30 seconds to quiet down also seams like alot. You may also need a tensioner as well.

at 210K mile you are breaking into new territory. Not too many people have gone above 200K mile so there is not a good data base to say if you are possibly reaching the limits of the lower rails. One of the lower rains pulls around a curved rail like the tensioner rail so it will also wear. The rest of the rails merely act as a backup to stop chain vibration.

My plan at 200K miles was to pull engine do all rails, timing chain and oil pump chain. Clean engine bay and reseal engine.

[Tom McMenamin]

The car spent the last week at the mechanic. Removed starter, Checked Flywheel, replaced Thermostat. Observed car for 3 days.

Yesterday morning at start the whack happened again this time not as loud and car started along with the sound. (Didn't need to shut down or grind the Starter.) Still have the miss at start up does not last as long now maybe 10 seconds.

Car runs great following the "bump" at start up and confounds me at this point.

The Timing chain was replaced along with Guides etc. at 130,000. The idiot who replaced it bent a valve and I did a top end at 130,000 miles as well.

No leaks found anywhere. Coolant and cooling system pressure has been reduced with new Thermostat. No Garage floor coolant leaks anymore. A positive.

I'm beginning to believe that it is a chain guide issue. We look at it all the time, due to my paranoia. Every time I get a repair we chack the chain etc. That's why I am doubting the chain as a problem, but I'll get it reviewed one more time.

All help would be appreciated here. By the way, the flywheel on the 1988 560SL does not have magnets. That was bad info from someone.

I'm gonna check the "Search" one more time and see what we have. All points of view graciously accepted! Thanks!

P.S.When reviewing the "chain" what are the parts that if something was awry on the chain, or guides, or whatever to check that I may have overlooked?

[Tom McMenamin]

Just started the car, White smoke is back! Stops after car reaches operating temperature. Coolant is still OK but appears down from my last check of two days ago. Pulled oil stick and I can't see any moiture contamination. The smell of the smoke is almost definietly moisture.

But when I say White Smoke, I mean White Smoke and lots of it.

So let me recap!

The problem started about two weeks ago when the smoke first started. Started car one Sunday AM after sitting for about 2 days and the White Smoke came bellowing out. Prior to the smoke, I was getting a lot of AntiFreeze on the garage floor and coolant was going out at about 1 gallon per month. Found a leak in the Radiator, so replaced the Radiator. As well, replaced 4 injectors on passenger side due to miss at idle.

Idle corrected with injector replacement, but returned at start up to miss for about 30 seconds then it smoothed out. Miss is still there at start up.

Following this service is when I heard the loud Thwack sound emanating from front of car. Smoke returned shortly after the injector replacement and so replaced the Transmission shift sensor. Felt that ATF was being sucked back into the system causing smoke. Eliminated the Cam oiler which might have occurred at injector replacement. Seemed to subside and then it returned. Not all of the time but every once in awhile on start I would get a lot of White Smoke. Again at operating temp it stopped.

Took car back to shop. Seems that the cooling system had significant pressure so replaced thermostat.

Following all of this, car expereinced another thwack sound at start. Not as loud as before but the same sound. This time I didn't need to restart as car started simultaneously with the noise. Previous 2 times it took 2 starts to get it to go following the noise. When the key turned, car would give nothing except a slight Starter turn. Everything lit up and after 2 tries car started.

Today on initial start White Smoke returned. Again at Op Temp it went away.
On return from clearing the smoke, pressure is up again on the cooling system.

Can find no leaks under the hood, garage floor almost dry. Not even any Air Cond overflow.

I must have more than one problem. The mechanic I use has always been really good. Never threw parts at a problem always went thru step by step diagnostics. Still does. Wouldn't replace the Trans sensor until we proved that nothing else seemed awry. I know this is contrary to the previous but he is a sharp guy and I trust him. I just think he is a buffaloed as me. Problem is that it seldom smokes for him, and he hasn't experienced the Thwack noise. Naturally the car performs well after warm up and runs better than ever.

Sorry to keep posting but I'm really at a loss.

[tk0084]

Well, it seems to me that if the mechanic doesn't have the same issues that you do then why not set up a video camera, start recording & then start the car. If it thwacks & starts smoking then you can get out & move the camera to other angles. Open the hood & show in there, the back end smoking, etc. This may assist your mechanic if he is unable to replicate the situation.