Okay here's the rundown:

Daughter's '81 300D sometimes felt like it was misfiring on one cylinder. She was doing a good job watching oil, coolant and everything. You know part of her learning to maintain a car.

She called from town, twenty miles away, and it had overheated. She had shut it down on the spot, "good girl".

When I arrived with gallons of water and tool box in hand, I could find no leaks or anything. Refilled the radiator, left water with her and followed her home.

It would overheat on the twenty mile run thereafter, same fire drill, and I believe that it was at this time that the misfiring cylinder became permanent. I told her not to drive it while I was on vacation. At this point, I could not find oil in coolant, or coolant in oil.

After coming back from vacation, I loaded up water and ramps, and drove twenty miles to the car wash to wash engine compartment thoroughly before tearing everything apart. It ran cool with no problems, even with 100 degree outside and running a/c. both ways. It did still have the dead miss. Still no coolant in oil or vice versa.

At this point, I loosened each injection line, one at a time, while idling, the engine seemed to falter equally on every one.

Was 90% convinced that I would find a dead cylinder when doing compression test. Tested compression this morning to find four cylinders between 280 and 300 psi while number 3 was 340 psi.

Now I'm totally perplexed. If the overheating problem was not involved, I'd think that the thing to do would be to dive right into the injectors or injection pump. When I moved the car out of the shop this morning to sweep underneath before tearing it apart, it still had a dead miss when cold.

Should I warm the engine and retest compression, even though it has the dead miss even when cold.

Any thoughts or previous similar experiences will be appreciated.

Wish me luck,



------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Hi Larry
This is guessing. Could something be off in the accelerator linkage?
I was wondering if faulty timing in diesels can make them overheat as is possible with gas powered cars. But your overheating is intermittant. If the accelerator linkage is catching or slipping maybe the pump and the throttle aren't working together the way they're supposed to.
Also - what was the last work done on the car? Sometimes the root of a current problem is in the last work.
Good luck and hope whatever it is is minor,
Harvey

Larry,

could it be possible that you got a batch of bad fuel and clogged up one of your injectors? This happened to our '82 240D. It ran like it was missing, but on acceleration you can almost hear a sort of nailing. I later found that the bad injector had the pintle, or needle, seized inside the injector body. Good luck finding the problem.

Nolan

Larry, I'd lay my money on an injector going bad. When you pulled the lines was the miss still present and if it was, there should of been one cylinder that stood out like a sore thumb. Another thing that comes to mind is a bad cam lobe (hope not!!)

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

[This message has been edited by jeffsr (edited 07-29-2000).]

That's one of the puzzling things, when loosening the supply lines at the injectors, they all reacted the same, no faltering.

If a cam lobe were flat, it would seem that it should have shown up in the compression test.

Is there anyway to test the injectors without taking them to the Bosch center and having them tested. I know that they calibrate them and all that, but if it's an injector, it's absolutely dead.

I still go back to the overheating. I sure was expecting a blown headgasket.

Thanks for the responses, please keep them coming everyone.

Wish me luck,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Larry, if a cam lobe was worn, but the valve was still opening, the choke on either induction or exhaust wouldn't necessarily show at the low rpm's that the starter will produce. Once the engine gets going, the choke will be evident as the partially opening and closing valve will now make it's presence known. Just a thought. Maybe remove valve cover, get a dial gauge and measure the lift on each valve..

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

jeffsr,

I think if a camlobe is bad enough to cause the problem, I will probably be able to see it without a scientific test.

I adjusted the valves for her not long after she got the car, but I wasn't paying any attention to camlobes particularly. The valve cover will probably have to come off anyway, I'll probably go take a look. If I don't find anything else, then I'll use a dial indicator.

Thanks for mentioning this. I need some things to make me think "outside the box".

Wish me luck,


------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Did you solve the overheating problem?

If you had a single cylinder misfire, due to any reason, it should show up in your cylinder balance test.

Is it a single cylinder misfire?? Cylinder head cracks let water into the chamber and cause misfires at idle. If they were large enough to misfire beyond idle they would eventually fill a cylinder (while shut off) and prevent starting due to hydrostatic lock.

Timing issues can cause overheating; did the overheating go away? If so thats not an issue.

Hard to make recommendation against the data supplied. If you have a single cylinder misfire it should act like a single cyclinder misfire.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Steve,

The overheating went away at least for two twenty mile trips on hot day with a/c on. Temp was at about 85 degrees C all the way, both ways.

The misfire is at idle at low speed, at high speed, any time.

You say that the miss would show up in cylinder test, could it not be an injector, or something injection related? Is it your experience that injection system problems just don't cause a dead miss. I've never experienced a dead miss in a diesel, so I'm on unfamiliar ground in that regard.

I am still very concerned about the overheating, but it did temporarily go away.

Also the miss is so bad that it makes a resonant soft vibration at highway speed.

Thanks very much for your reply,


------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

>The misfire is at idle at low speed, at high speed, any time<

Does this statement mean that it misfires at all speeds?

Almost anything can cause a single cylinder misfire. You should be able to identify the single cylinder by cracking each line loose and noticing the difference. The cylinder that doesn't work won't make any difference when the fuel flow is diverted.

If this doesn't work then you most likely don't have a single cylinder misfire.

You don't have a couple of gallons of gas in that diesel do you???

Larry,
Wish I hadn't read your post just before going to bed. Been lying awake for hours! :confused: You asked for any thoughts, so here are a couple.

Overheating: The only thing that comes to mind that would cause intermittant overheating is an intermittantly functioning thermostat. If it were mine, I would install a new one and await further developments.

Missing: I would be very suspicious of injector problems. Two possible courses of action (if it were mine). (1) Dismantle, clean and check each injector in accordance with MB manual or (2) obtain a rebuilt injector, install it in number 1 cylinder, check operation. If no improvement, install injector removed from number 1 cylinder in number 2 cylinder, check operation, etc. This wouldn't take a lot of time and when you got through you would know for sure if it is an injector problem.

As is so often said on this site, "Just my $.02 worth." Best of luck!

------------------
Ted
1979 240D
160,000 miles

[This message has been edited by Ted2222 (edited 07-30-2000).]

I tried breaking loose all the injector lines at idle and found no difference. However, that was earlier when the misfire was not as pronounced as it is now. I'm gonna try it again.

Although my daughter is pretty sharp and aware, at least for a sixteen year old, the gasoline is a possibility. My son who is twenty and a college student who knows more than anyone else on the planet (at least in his mind) has driven the car some. He would be much more likely to have added a little gasoline.

I've never had a thermostat intermittent, but if someone else has seen it, it must be possible. I have a good thermostat and it's easy to change.

Thanks for the responses, I will check a few more things. But keep the thoughts coming, I appreciate everyones help very much.

Wish me luck,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

I just put the injectors back in, started it and cracked each line individually at idle. It faltered on every cylinder. There did not seem to be one that acted any different than any other.

The vibration is bad and feels like a dead cylinder. I'm completely perplexed about the miss.

In looking back at the log book and speaking to my daughter I found a time where my son put 2.50 worth of diesel in. My daughter said he did that a country store out here. The pumps are not marked well and I'll bet he put gasoline in it. Maybe that explains the previous overheating.

I really don't know what to do at this point. Do I put injectors in to see what happens?

Thanks for any ideas anyone may have,


------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Try a can of Lubro Moly Diesel Purge. Run the engine directly off the can. You'll get a good cleaning and at the same time you can isolate the fuel. By doing that you can see if indeed you got a batch of bad fuel, or gas, mixed in.

Does the car smoke a lot? When I had a bad injector in my 300SD, it shook like it was missing and smoked more than usual at idle. I too cracked the lines one by one and almost didn't notice any difference except in the #5. I pulled that injector and opened it up,the needle was really tight, almost seized. A rebuilt injector cured that.

I'd try the diesel purge first before messing too much with the injectors. Your son could have gotten some really bad fuel at that country gas station. This way you can isolate any bad fuel from the tank and the same time get a really good cleaning of the injectors. Good luck.

Nolan

Came home this evening and tried cracking the injector lines again, and could not find a cylinder which acted worse than any other.

In the course of all this I have come up with two findings;

One is the engine no longer overheats.

The second is that I don't believe it is a dead cylinder. There is a vibration that you can feel sitting in the drivers seat holding onto the wheel. It is very pronounced. When standing at the engine reving it up, you can hardly tell that there is anything wrong. The reason I have thought that it was a dead cylinder is that the vibration is at engine speed. It's like the torque converter or harmonic balancer are heavily out of balance.

I'm still stumped. Driving down the road is brutal, the vibration is so pronounced that it warbles. If you've ever sat between two airplane engines both at slightly different speeds, that's what I mean by warbling. The vibration goes in and out, in and out.

It is so bad I won't drive the car, or let my daughter drive it. It feels like something is going to tear up.

I've thought motor mount, but even if the engine were welded to the body structure, it shouldn't vibrate this bad.

The harmonic balancer runs smooth visually, is tight and seems to run out perfectly.

I'm totally stumped,

Thanks to everyone
Larry

Hi Larry,

Sorry to hear all these bad news. Is possible that a bad flex disk causing the vibration? If it is, it should happen only when the car is moving.

Good Luck

David



[This message has been edited by be459 (edited 07-31-2000).]

Hello again, Larry,
I, too, am sorry to hear of all your current problems. While I have no idea of what may be wrong, may I suggest that you put the car up on a rack and get underneath so you can observe, feel and listen to the drive train while in operation? Wish I had something better to offer.

Good luck.

------------------
Ted
1979 240D
160,000 miles

Back again- -grasping at straws: Are the water pump shaft and fan solid?

------------------
Ted
1979 240D
160,000 miles

Folks,

Thanks for the continuing thoughts and responses.

My next session with the car, which will probably be tomorrow night, I will take off all three belts, crank it and rev it up once to see if the vibration goes away.

If it were the flex plate, it would seem that it would happen when you rev it up, wheter or not the vehicle is under way.

Thanks everyone, I haven't set it afire yet,
Larry

PS When I think further about this. The vibration is so bad, I believe I would see a heavily pulsating belt if the problem were an accessory. I will try it anyway. LB

[This message has been edited by LarryBible (edited 08-01-2000).]

Didn't get to the daughter's car last night like I said, had other car problems, this time with an American piece of #@(&.

But I was wondering, those of you who have lost a harmonic balancer from a 240D or 300D, was there noticable vibration for any period of time prior to the catastrophic occurrence?

Thanks for your responses,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

[This message has been edited by LarryBible (edited 08-02-2000).]

I would rethink the motor mounts. If the center has fallen through they transmit a tremendous amount of noise/vibration as the metal of the mount beats on the frame.

I have seen about every balancer problem imaginable including wrong oiut of balance balancers and can't imagine one causing the problem you describe.

Does the engine seem to be running properly other than the vibration? Is the power OK? A diesel with a big timing problem will shake terribly and not be related to single cylinders.




------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Steve mentioned timing. What about the injection timer in the sprocket that drives the injection pump. Could it have jammed? As an aside, has anyone had a problem with an injection timer? Do they wear?

Steve,

Thanks very much for sharing your experience. Although it may need mounts, the vibration does not feel metallic in any way. I will do the drip method timing check, it will at least find any gross error that may exist.

Vince,

My experience has been that once timing is set nothing changes it very much until overhaul time unless there's some big problem. However, my experience base in this area is limited to a half dozen 123 diesels. It would seem to me that if there was any jamming of the chain in the pump area, there would be catastrophic failure, or at least an engine that wouldn't run.

Thanks to everyone for the continuing input,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Actually Larry, I wasn't thinking of a jammed chain, but a faulty timer. I think the injection timer acts to advance the injection timing as engine RPM increases. I've never had one apart, but from the manual it appears to be a "centrifugal advance" mechanism built into the sprocket that drives the pump. I know it is a reach, but when Steve mentioned timing it made me think. I've always wondered if the timers wear and if that could explain the erratic nature of the idle on my 1983 240D. I've checked everything. One day it idles like a gas car, the next day I shakes so much you would think it's going to tear itself out of it's mounts. It's going to be interesting to see what you find. Good luck!!

vince,

Thanks for the thought. Theoretically it seems to hold water. I'll be interested to see if any of the pros have ever seen something like this.

Thanks,
Larry

Larry,
In response to your question several posts back: I have lost three harmonic balancers on my car and there was never any warning of any kind. One second everything was going fine and a second later the whole thing was in pieces.

------------------
Ted
1979 240D
160,000 miles

Same here with my three harmonic balancers. Well the second time I thought that the engine sounded funny, but thought it was loose belts slapping around, 10 minutes later the bolt was broken, and I was broken down. On my motor, before I bought it, two pistons were replaced, the #1 and #5. #5 had a bad valve, #1 was loose inside of its walls, although you couldn't tell with the head off. So far its still sitting ina corner waiting for the balancer problem to be resolved. But I may have come across a donor car. BTW if you need a non turbo 300 crank, i got a used one....cheap! and a rebuildable block
Good luck with your hunt, I am curious as to what you find.
-Larry

------------------
03/83 300D 184k
07/73 280 160k
-88 other 153k

Thanks for the harmonic balancer feedback. If you've been reading along, I am anxious to check the timing. I will do that Friday night before I get into my 240D clutch job Saturday, which reminds me of another post I need to make.

Thanks to everyone and have a great day,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Well, I checked the timing and it was at 20 BTDC, I changed it to 26 with the drip method.

Same ol' thing.

I guess I'll try the purge and/or a set of injectors. Actually, I have some injectors that aren't great, but they work, I may try them to see what effect they have.

This one is really wearing me out. I don't mind doing work on these cars, but when I cant' determine what to do, that's the most frustrating part.

Thanks for the help everyone,
Larry

Larry, I know you said that you adjusted the valves when your daughter first got the car, but, maybe you want to eyeball them again,...just to make sure.
Just to go over a few things...the oil nor the water is contaminated. Fuel timing is ok. Injectors appear to be injecting. This leaves either the valves or something awry in the bottom half...however your compression check would want to steer you away from the bottom...hmmm. :confused:
I know I didn't come up with any earthshattering revelations, but sometimes going over the details can get us distracted enough to fall on to the right track.
-Larry

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03/83 300D 184k
07/73 280 160k
-88 other 153k

Larry -

I have been following this and the only possibility that I can think of is that something might have go wrong with the torque converter or flywheel.

Clearly a long shot, but what's left?

I once had a Corvette that had the same sort of weird vibration, and it turned out that half of the clutch disk was gone.

Good luck - this has to be horribly frustrating.

Chuck

May I be so bold as to point out one other thing that has been suggested that, as far as I can tell from the various posts, has not been checked out? That is the possibility of contaminated fuel. The purge treatment may give some insight on that or running the engine on fuel known to be good while the hoses are set up for the treatment.

Another of my $.02 worth.

Larry, for goodness sakes, get this solved! We are all going nuts trying to figure out what's wrong. :)

------------------
Ted
1979 240D
160,000 miles

I'd like to explore this harmonic balancer problem some more. I've lost two on my 1979 240D. The first time it took out my radiator, the second time luckily it missed. I've never seen this before on other types of cars. How common is this and why does it occur? Are the bolts loosening or shearing, or is it just a bad design?
Thanks for any input.



------------------
Steve
1979 240D
1990 300E

Steve,

You have asked some questions that really go into the quick with me. First, what happened: I had the crankshaft oil seal replaced on my car to stop a leak; that was the beginning of my problems. After the balancer came off the third time in the next 20,000 miles, I pulled the car home and called the area Mercedes Service Representative. (All the repairs had been done at dealerships.) I told him what had happened and that I was at a total loss as to what to do. He made a special trip to my dealer the next day. Ordered new parts by air and conducted a seminar with the service department techs on how to install the harmonic balancer. He had them strip away all the parts right down to the crankshaft and reassemble it with all new parts. It seems critical that the correct torque is used on the bolts and, I think, some Lock-tite was used. Once the dealer had done this, I took it upon myself to back off on the tension at which the belts were set. MB specs call for extremely tight belts. I reset them only to a tension at which they would not slip. I even instruct the dealer service shop not to set the belts to specs. They know instantly why I make that request. So far, there has not been another incident and that was about 55,000 miles ago. I still can't help wondering if it is going to happen again, however.

If the "incidents" resulted in crankshaft damage, I have been told that the only permanent fix is a new crankshaft. Let's hope that hasn't happened.

Now, for my opinions. From talking to people at the dealership and from reading this forum, I get the impression that it is not an unusual occurance. The problem? I think mine stemmed from the fact that no mechanic (technician?) who worked on my car knew the correct procedure for installing the balancer. I also get the impression that the design is not all that we are led to believe we are getting when we buy one of these expensive automobiles.

Anybody have some different ideas?

Hope this is the information you are seeking and that your balancer won't come off again. Good luck.

------------------
Ted
1979 240D
160,000 miles

The 616 and 617.5 motorsdo have a number of balancer problems. The 240D usually has the bolts shear holding the lower belt pulley to the crank. These repair quite easy.

The other failure; the balancer, itself, falling from the crank is usually after a repair. It is also much more critical as the balancer usually removes some of the crank in its way off. The balancer should be a tight fit and we use a factory tool to pull it on. If the pulley slides on or is turnable (without alignment dowels)by hand it will have future problems.

Now that it seems many of the good suggestions have come out, here is maybe a dumb one, at least for the overheating. Would it be advantageous to drive the engine with NO thermostat. If it still overheats, you know it ain't that. I once pulled a thermostat and notice someone used the end of baseball bat as a flow reducer!!!!!!

------------------
'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)

Sorry for taking so long to respond on this. Thanks Ted and Steve for the information regarding the harmonic balancer. You have provided some valuable information.

My first balancer failure occurred a year after a (factory?) rebuilt motor was installed. The balancer and radiator were replaced by a non-Mercedes shop (happened out of town). A year after that replacement, it failed again. This second time it was replaced by an independant local Mercedes specialist shop. That was 3 years ago.

I'm wondering if it would be a prudent course of action to replace and retorque the bolts every year or so? Any comments?

Thanks

------------------
Steve
1979 240D
1990 300E

[This message has been edited by dakota (edited 08-20-2000).]

Steve,

Your suggestion of replacing and retorquing the bolts periodically leaves me with mixed feelings. While the idea certainly has merit in attempting to keep the situation under control, I can't shake the feeling that once it has demonstrated stability, perhaps it should be left alone. You know, if it ain't broke, don't fix it.

Perhaps some our more learned and experienced comrades in this forum will favor us with their views on this?

------------------
Ted
1979 240D
160,000 miles

Larry,does the vibration change when changing from drive to reverse? When pushing "EC" and then the middle ACC button again? Have you tried slightly unloading the engine mounts and rear trans mount while the engine is running w/ the daughter inside to listen for changes in pitch or tone. Does the car have the "capture mount" right behind the oil pan? If so . slip the retainer clip off of the 19mm bolt head and loosen the bolt about three turns then retighten it.Also, the rear mount has a 6mm tool size allen facing aft. Do the same this bolt, then grasp the drive shaft and pull down.You should perceive 3-5mm deflection. If not, replace the mount.
If this is more of a felt vibration than audible, a torque converter rotor bearing failure may be the deal, and will have sluffed off swarf throughout the transmission. u know what that means.
Check the easy stuff 1st ( u know that too)