Misfire and Smoking in 98 e300
 

My brother in law bought a 82,000 mile car that was repaired after a rollover accident for a very reasonable price on account of a misfire and smoking. We have had the vehicle at a independent shop and then at a dealer. The car seems to run much better upon startup but we think this is due to the glow plug system. The car has been driven several hundred miles with no change.

The independent shop, a diesel experienced tech, checked many things and diagnosed a faulty injection pump. The pump was ordered and installed but did not help with the misfire and smoking when warm. The original IP is now back in the vehicle.

The car was then taken to a Mercedes Benz dealer and was diagnosed with leaking injectors. New injectors were installed but the problem did not resolve itself. After some delay and a complaint that a compression test was not done, the dealer performed a compression test with the following results: Cylinder 1 - 25 bar; Cylinder 2 - 21 bar; Cylinder 3 - 19 bar; Cylinder 4 -22 bar; Cylinder 5 - 25 bar; Cylinder 6- 19 bar. Cylinders 3 and 6 were repeated wet and the compression remained 19 bar for both. Based on low compression, dealer is concluding bent rods!? They are not a 100% on valves but think the head is OK. The have since removed the new injectors and placed back the old ones - a class act by a dealer!

The only code that remains is a engine misfire. Before we either agree to a tear down or flip for a used engine, any and all thoughts would be greatly appreciated. We are also considering marketing the vehicle as a last resort.

JC

If the engine was running when the car rolled, It is very possible that there are bent rods. I have replaced several Om606 Diesel engines that have
bent rods from oil being in the wrong place at the wrong time.
Like being sucked throught the PCV system and hydrolocking the engine.
(jiffy lube pumping 8qts into valve cover and firing up asap.)
Pull the head and check piston deck height to see if there is a difference in
height on 3 and 6. Cylinder wall wear may be heavy in those 2 holes as well.
Junk yard motor may be in your future.
DR.D

Dr Diesel:

any chance that this is caused by incomplete combustion deposits requiring lots of driving to clear up?


Can anyone recommend a place for a used engine? I found several over the internet but am not sure if reputable or if just a bunch of middlemen!

TIA

jc

If there are deposits in the chamber, wouldn't that drive compression up instead of down?

The head may have some value. Perhaps you can work a deal to let the people that sell you a used engine take something off for your head assembly. If they are in the business really they may be interested. Not sure of demand for your head type though and that would determine the price. Just something to keep in mind.

aklim

I am told that the deposits affect the piston rings to the point where the sealing of the rings loses its effectiveness. Basically, you have muck. These are just guesses and grasps at last straws.

Dr. Diesel:

I am told by a MB tech that every car has some sort of sensor which cuts everything off at a certain angle from right side up. If that is the case, then the car, theoretically, would not hadrolock itself. The other possibillity is that there was an attempt to start it immediatetly after the tow truck put it right side up again. This scenario could cause the damage we are discussing.

JC

I suspect the guys meant that the oil went into the cylinders or at least some of them through the valves when the car was upside down and running. The opinion I would seek now is if some of the bores are damaged or just putting new rods in the engine might work. Unfortunatly the rods are at a better than 90% chance of being bent from your description and others experience. I agree it is too bad. Nothing good only increasing damage may happen from driving it any more now. I would tear down the engine and have a good automotive machine shop guy check those bores carefully if there is no visable damage. Even a little damage in say two of the bores might be dealt with by a slight overbore and two new pistons. Afterall the engine only has 82k. But to make it financially viable you have to get your hands dirty I personally would take this option unless a lower or simular milage engine was available that one really could establish was a genuine low milage engine..And needless to say the price was right.

i agree
 

with barry.

another innocent injector pump pulled. ditto for the injectors!

tom w

Assume that the fuel shuts off when the car is inverted. The engine was turning when the sensor shut it off. It doesn't just stop dead, since there is a lot of inertia in the parts. So there is absolutely no theoretical reason why the engine could not have hydrolocked.

You don't generally bore two cylinders, unless it's a two-cylinder engine. Replacing sleeves is another story.

Considering that the car still has a bit of book value, and I am sure used 606's are not cheap. Have you priced out a short block from say the a MB dealer, or a rebuild from Metric Motors?

I'd bet $3-$4k would get you a new/rebuilt bottom end.


Since it only has 82k miles on it I'd just bolt the old head right on. I wouldn't even bother touching the valves.

Yes I agree it is not perfectly ideal to bore two cylinders a small amount over if it were required. On the other hand it will not affect the power balance enough to worry about in my opinion. I am assuming just slightly larger pistons if possible as I think the pistons are so mallable and flexable compared to the hardness of the sleeves. That is unless he drives it a lot with the present defect. Think of the 3.5 litre with the bending rods. There is only the slightest damage initially but over a long period it gets out of hand. With a little luck all six bores are still good. Replacement sleeves come into play if it is determined the bores are either distorted or massivly chewed out of round or some simular effect.

That would be my advice as well...get the tech to pull the head and confirm the rods are bent by checking the top-clearance as one of the other posters had suggested...once that is confirmed get a new short-block and have it changed. Don't mess with it any more.

It's a shame the person who had the accident didn't know about it at the time, the insurance would have covered this damage as well.

And potentially just sent the car to the crusher.

Considering how precise these engines are and how MB matches piston sets. Just having two cylinders over bored will make it run like crap.

Their is a difference between rebuilding a MB engine to Chevy vs factory specs.

Thats why sometimes it is just better to buy a new short block with a warranty, might not cost much more.


Remember a crate 606 probably costs as much as a new Malibu. There is a reason these engines last so long and run so well.