Long and painful - PeachParts Mercedes-Benz Forum

lilblkbnz · #1 02-27-2006, 09:25 PM

Hello again everyone. I've been a member here for quite some time but haven't posted in a long time. I crossed over to the diesel side for a while, 84 300sd. Liked it a lot but recently relocated to New Jersey from Oklahoma so I sold the SD prior to the move. When I got here I found and bought an 89 420sel, 136k miles with some records. The car seemed fine, good interior and exterior. The only problem was blue smoke on startup and oil consumption of about a quart per 800 miles. Soooo, two days ago after reading all I could on this forum I decided to replace valve seals. All went well and no more smoke on startup or any other time. Pretty proud of myself since I'd never done this job before. Then reality set in. The next day the car starts normally and I go for a drive, about 20 miles of interstate driving at 65-70 mph, then stop to fill up. When I pull into the gas station I hear a tapping sound from the right front of the engine. Kinda sounded like lifter noise to me, but I'm no expert. I drove the car home and by the time I get home the noise is gone. So I'm thinking maybe a piece of dirt stuck in the lifter and worked it's way out or something like that, no big deal right? Wrong!! Once back at home I notice the car is now running rough. It's dark out so I take a peek under the hood with the engine runmning and I can see a nice blue glow around three plugs. Plug wires shot, so I ordered a new set, haven't gotten them yet. I decided to take the car to the store around the corner and the tapping is back, only worse! I drive it nice and easy and the tapping comes and goes. But now the car is missing even worse and the noise gets louder. It now sounds more like a bolt was dropped into the engine! I get to about a block from my driveway and the noise stops, because the engine died!! Now for my question, do you guys think the timing chain went?? I had no symptoms before, no slapping at startup, nothing. I haven't pulled the valve covers to look at the chain yet, the car is still on the side of the street. I didn't even try to restart it, I was so heartbroken I just walked home. HEELLLLPPPPP!!

t walgamuth · #2 02-27-2006, 10:37 PM

about the problem.

no way to really tell anything til you get more facts.

good luck

tom w

Two560Two · #3 02-27-2006, 11:08 PM

Just hopefully the chain didnt break. Lets just pray. At that mileage, its bound to go. I have got 3 126 V'8s and 1 107. I have more to worry about than you do. When you changed the valve seals, didnt you have the valve covers off anyway? I guess you could of checked the chain and tensioning rails. As for the blue smoke on the plugs, I have never heard of a timing chain break and then having 3 plugs going bust.

lilblkbnz · #4 02-28-2006, 06:23 PM

I just pulled both valve covers off and the timing chain appears to still be in place and tight. The rails do look brown but they are there and I can't see any broken ones. I had recently ordered a new chain and rails and I got them today. Now the problem. When I got in the car today it would not turn over. Sounded like the motor was binding somewhere. It only clicked when I tried to turn it over. It was about a block from home so we used another car to push it home. When we got there I tried one more time to turn it and it turned over. But I had the plug wires off so of course it didn't start. It turned a couple of times and seemed to bind again. What could be causing the binding?? If the timing chain isn't the culprit what else could it be?? Something else wierd, there is oil all over the passenger side valve cover. The gasket was just replaced and wasn't leaking before. Any ideas would be greatly appreciated.

#5 02-28-2006, 07:09 PM

First thing is to discover if it is really binding; the clicking could be caused by a bad connection, old battery, poor alternator, etc.

Why not pull the plugs and turn the engine by hand? If at that point you feel binding, I would look at the work I just completed and make sure all nuts are back in place (properly torqued), all the seals are still where they are supposed to be, etc.

Try to be as systematic as possible in your troubleshooting!

cheers,
dan r.

EDIT: +1 for 'Keep 'em seperated!'

thorsen · #6 02-28-2006, 07:38 PM

I know it's not as much fun as tearing into an engine, but remove all the belts from the front of the engine. I have heard a lot of stories on here about AC compressors, alternators, and water pumps that have siezed and prevented the engine from turning.

lilblkbnz · #7 02-28-2006, 07:54 PM

Thanks guys for the quick responses. It's too dark to do anything else tonight but I will try all suggestions. With any luck it'll be something simple. I've only put about 4k miles on this car. No chain rattle on startup, no missing, nothing other than smoke on startup. The PO took pretty good care of the car but says the chain wasn't changed. He does claim oil changes every 3500 miles and the tranny was serviced just before I bought it due to a leaking pan gasket. I was able to look around the rockers and springs and everything seems to be in place. I'll dig deeper tomorrow and post what I find. Thanks guys, and please keep the suggestions coming. Anything is worth a shot. And yes, I do all my own wrenching, kind of a hobby.

Al Magaloff · #8 02-28-2006, 07:55 PM

Valve guides= oil consumption/ intermittent ticking noise.

lilblkbnz · #9 03-08-2006, 08:36 PM

Guys, I just pulled the heads off and found the number 4 piston is completely gone. All that's left is the connecting rod and wrist pin. Even those are twisted badly. But the timing chain is till intact. So this wasn't a chain issue. The car has 140k miles. Any idea what could have caused this. Oil pressure was pegged at 3, temp was normal at about 82. And this all happened at less than 25 mph. I know the motor is trashed but I'd still like to know the cause. Soooo, I'm looking for a good used engine or more than likely another 126, maybe I'll get lucky and find a nice 560sel. Or what about putting a 560 engine in the 420? Would that be possible?? I'm open to almost anything right now. Let's hear what you guys would do. Thanks everybody.

Al Magaloff · #10 03-08-2006, 09:16 PM

Are both valves still in the head, or did one of the valves in that cylinder fail?

t walgamuth · #11 03-08-2006, 10:15 PM

bad luck. sorry to hear it.

not to be too simple but you didnt mention checking the oil level.

the 560 and 420 should be physically the same from the outside so they should interchange. were they ever offered the same years? i always like to swap the same year engines if possible to minimize electrical differences.

good luck in whatever you do.

the only two things i can think of that would disentigrate a piston are as noted above, a dropped valve or very lean condition on the fuel mix.

tom w

suginami · #12 03-08-2006, 10:39 PM

The 560 and 420 were sold in the exact same years '86-'91.

I don't believe they are the same block. One is a big block and the other is a small block.

They even have different engine codes: M116 and M117.

lilblkbnz · #13 03-08-2006, 10:45 PM

Oil level was fine, changed the day before this happened, still shows full. Well a little over full now that theres some coolant in the oil pan. The exhaust valve is still in place but all that remains of the intake valve is the stem. The rocker arms were all still in place and the cam doesn't appear to have any damage. I hate to say it but I'm seriously thinking about going back to diesel. I'm looking at an 84 300sd with 134k with records from 20k to present. It may turn out to be my driver so I can slowly put the 420 back together the right way. I can get the 300 for 2500 bucks or less because the owner is being re-assigned overseas and can't take it with him. It's a very nice car. What do you guys think?

t walgamuth · #14 03-08-2006, 11:08 PM

nice.

i have never heard of mb big and small block v8s. the 380 and 500 were same blocks and identical (nearly) externally. the 560 too. i dont really know anything about the 420 but find it tough to believe it is much different.

tom w

Al Magaloff · #15 03-09-2006, 05:26 AM

Many valves are spun welded together where the stem meets the head . It would be upsetting to find that MB valves were not one piece, but welded. I have never seen a one piece valve, intake especially, fail in that way. The connecting rod bent when the valve head dropped and was smashed by the piston. I think the MB cast iron turbo diesel is one of the best motors ever made. My "collection" has begun with an '83 SD, with a few more cars on the horizon.