Melted Pistons, etc

New member here, just posted a hello in the general section and figured I'd head over here for some troubleshooting help. I've got two 2004 Jeep Grand Cherokee 2.7 CRDs in Kyrgyzstan. The motors are OM647s, so I'm hoping this is the place I can get some good info on them (I know their not Sprinters, but we can't all be perfect). One of the Jeeps started acting up toward the end of the summer. I wasn't driving, but my client reported that it made a ticking sound at the top of a 3300 meter pass (about 11,000 feet). Since everything looked ok (temperature, oil, water, etc) we decided that he should keep going. He got about 150 km down the road when a massive amount of oil poured out of the coolant overflow. He reports that it didn't overheat, but I'm really not sure. We swapped him out for a different car and put the Jeep on a truck back to Bishkek. After trying to eliminate the normal culprit, the heat exchanger, things still weren't right so we pulled the motor. When the head came off we discovered two melted pistons. #4 is badly melted and #3 is a bit melted. Both scored the cylinder walls as well. The only known issue was that injector #2 or #3 (I can't remember) was just starting to leak a little (classic black death) and was to be fixed when he got back.

The jeep has 129,000 km on the odometer and was running fantastic up to this point. Regular oil changes and it had a new fuel filter. There's no visible damage to the head, though we need to pressure check it. I'd like to just swap motors at this point, though I'd also like to get a better idea of what happened to prevent such expensive failures in the future.

Here are a couple pics of the pistons and cylinders.




Note that not only is the outside edge toast, the inside around the "cup" is also melted and deformed.

Regarding engine swaps, can anyone comment on the compatibility of OM612 and OM647 blocks? If I can get my hands on an OM612 engine, can I just swap on my components such as injectors, computer, etc? It seems the two are really, really close.

Hello and greetings.
Firstly I have only been to Kyrgyzstan once way back in the 1970's to look at a new Range Rover with British Embassy that had broken down.
I had to journey from Tehran where I was living to Moscow then to Bishkek.
It was quite a journey with Soviet Aeroflot as I vividly remember!

To your problem:- From the pictures it looks like numbers 1,2, and 3 pistons are affected mostly which is not uncommon. I see about three of four engines like this every year and in fact I am rebuilding two at the moment for customers.
In short you have a severe engine overheat condition, more than not created by localized heating of the forward cylinders where the cooling system needs close attention, such as belt tensioner,. serpentine belt, and viscous fan clutch. For info the thermostat will open at 90 dgc and the fan will clutch at 98/99dgc so careful attention should be paid to the radiator matrix as well since it maybe partially plugged up with dirt on the exterior and interior with solid deposits. Are you running just water in the cooling system or antifreeze mix to 50% strength?
But the problem I see on at least one cylinder is over injection and erosion of the crown and toroidal cavity.


When an engine is in severe overheat the tip of the injector is also affected and the injector can "hose" making the situation even worse as excess fuel is now being burnt raising cylinder temperatures way above the melting point of the piston material.

This is not all since it is advisable to see if you can extract any stored fault codes from the engine PCM. In those extracted codes maybe the other parts of the failure story; that of injection faults like fuel quantity valve , injection duration, or excessive injection.
Only by doing a complete analysis can you reach a point of failure conclusion.

Yes you can use the earlier block for the rebuild, but you will have to use all the later accessory and equipment since they are vastly different, such as injection , HP pump, and injection equipment.

If you have more questions just fire away and i will be more than willing to help.
Best regards
Dennis

lindenengineering said:

Hello and greetings.
Firstly I have only been to Kyrgyzstan once way back in the 1970's to look at a new Range Rover with British Embassy that had broken down.
I had to journey from Tehran where I was living to Moscow then to Bishkek.
It was quite a journey with Soviet Aeroflot as I vividly remember!

To your problem:- From the pictures it looks like numbers 1,2, and 3 pistons are affected mostly which is not uncommon. I see about three of four engines like this every year and in fact I am rebuilding two at the moment for customers.
In short you have a severe engine overheat condition, more than not created by localized heating of the forward cylinders where the cooling system needs close attention, such as belt tensioner,. serpentine belt, and viscous fan clutch. For info the thermostat will open at 90 dgc and the fan will clutch at 98/99dgc so careful attention should be paid to the radiator matrix as well since it maybe partially plugged up with dirt on the exterior and interior with solid deposits. Are you running just water in the cooling system or antifreeze mix to 50% strength?
But the problem I see on at least one cylinder is over injection and erosion of the crown and toroidal cavity.


When an engine is in severe overheat the tip of the injector is also affected and the injector can "hose" making the situation even worse as excess fuel is now being burnt raising cylinder temperatures way above the melting point of the piston material.

This is not all since it is advisable to see if you can extract any stored fault codes from the engine PCM. In those extracted codes maybe the other parts of the failure story; that of injection faults like fuel quantity valve , injection duration, or excessive injection.
Only by doing a complete analysis can you reach a point of failure conclusion.

Yes you can use the earlier block for the rebuild, but you will have to use all the later accessory and equipment since they are vastly different, such as injection , HP pump, and injection equipment.

If you have more questions just fire away and i will be more than willing to help.
Best regards
Dennis

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Dennis,
Thanks for the very useful post. We weren't able to get much from the PCM (lack of proper equipment). It uses a Chrysler interface combined with a lot of Mercedes background data and the local scanners just aren't equipped to deal with it. We got some codes from the dash, on Chrysler models you can turn the key three times and it reads out the codes. They were all pretty generic, nothing about overheating. IIRC it was just the CPS (which comes on every time there's a low battery) and the fuel pressure regulator (which also comes on every time there's a low battery).

The cylinders affected are numbers 3 and 4, with 4 being the worst. As far as we know there was no obvious overheat prior to failure, it just failed suddenly, but I wasn't driving, so I can't be 100% certain. How long does it take for the kind of erosion to happen? Could this have been on ongoing over fueling issue that just suddenly came to a head? Also could a blend of gasoline and diesel cause this? (We've been given gasoline by a station before when they ran out of diesel...).

I plan to go through every system before we put things back together to make sure that we don't melt another engine.

Would have loved to see Kyrgyzstan back in the 70s when it was a little more "untouched." As it is, it is a crazy cool, remote place! You're welcome back any time!

kyrgyznomad said:

Dennis,
Thanks for the very useful post. We weren't able to get much from the PCM (lack of proper equipment). It uses a Chrysler interface combined with a lot of Mercedes background data and the local scanners just aren't equipped to deal with it. We got some codes from the dash, on Chrysler models you can turn the key three times and it reads out the codes. They were all pretty generic, nothing about overheating. IIRC it was just the CPS (which comes on every time there's a low battery) and the fuel pressure regulator (which also comes on every time there's a low battery).

The cylinders affected are numbers 3 and 4, with 4 being the worst. As far as we know there was no obvious overheat prior to failure, it just failed suddenly, but I wasn't driving, so I can't be 100% certain. How long does it take for the kind of erosion to happen? Could this have been on ongoing over fueling issue that just suddenly came to a head? Also could a blend of gasoline and diesel cause this? (We've been given gasoline by a station before when they ran out of diesel...).

I plan to go through every system before we put things back together to make sure that we don't melt another engine.

Would have loved to see Kyrgyzstan back in the 70s when it was a little more "untouched." As it is, it is a crazy cool, remote place! You're welcome back any time!

Click to expand...

OK
I see that you ran it gasoline! In the right combination of mix---And duration--- Yes it can cause severe erosion to pistons and injector tips. I ran across this in Iran where the Iranian Army was adding gasoline (petrol) to fuel tanks to aid cold weather starting in their Leyland trucks. It works, but it doesn't work! Depends upon the "mix" ratio! Melted pistons pretty quickly in some cases. AND it wasn't confined to trucks either, their Chieftain battle tanks with the Leyland L60 engine took a beating too! It was a multi fueller!
On of the issues is the "dryness" of gasoline which can cause injector nozzles to stick causing the injector(s) to hose. Anyway here is a short video it explains it all I think!

http://www.youtube.com/watch?v=K4_iMkT3IMo

In any case during your re-build pay attention to the cooling system & FIE, this forum has a lot of debates about when to change out serpentine belts and tensioners etc. All I can tell you is that the rule of thumb is 100,000 miles. I have seen this summer quite a few vans overheating due to cooling system shortcomings. Remember it doesn't take much to create steam pockets in the head which won't show up as an overheat on the gauge but it is distressing the engine.
I have all the torque specs for rebuilding so if you need those I can supply them when time requires.

Yes I remember it being a very remote place and I bet with more Yak transport than you have there now! Then, being a zone and tech rep for the M.E. I used to have to get in fix it and get out asap. Hence I didn't spend much time there and meet locals just hob knob with fellow Brits.

I spent 12 years in the area (Iran/Iraq /Syria G'han and much of the upper land area (Asia) strikes me as being very rugged and unspoilt. The stars at night are always a marvel and on some occasions when there was time off I would be out in my Landrover or on a scrounged 1956 Triumph Tiger 100. On one occasion I rode that that thing from Tehran to the Oxus River border post trying to get to Samarkand. ( they wouldn't let me in the country !)

Yes I suppose I wouldn't mind a revisit, this time with my American missus in tow who has wandered often alone around India and Pakistan when she wasn't flight attending with TWA.
It was one of the first attractions about her when we first met.
Stay in touch and all the best.
Dennis

Once again thanks Dennis!
The information is a life saver. Can't confirm or deny gasoline at this point. One of our other Jeeps got a full tank of gasoline this summer when the filling station didn't inform the clients that the pump marked Diesel Fuel actually had gasoline. Some sensor or other on the motor shut it down ASAP and after draining everything and purging it, we haven't had any problems (50,000 km this summer just on that jeep and the motor has been faultless). The jeep with melted pistons is still the mystery. We had an overheat earlier in the summer when an Uzbek Sprinter mechanic in Osh screwed up the belt. We corrected it quickly and had no noticeable problems. Temperature was rock steady around 90 celsius, oil pressure was fine, no warning lights or codes. In otherwords nothing until this melt down. The only thing else that my lead driver pointed out is that a diesel mechanic rebuilt two injectors last winter, and he thinks it's the same two involved in the meltdown. I'm going to have to go through those injectors carefully. What am I looking for? I'm a decent mechanic (lots of headgaskets and a manual trans rebuild have been no problem), but I'm mostly used to working on 80s and 90s American cars like Dodge Ram with gas motors, not diesels.

Whenever you want to come on out just give a holler and we'll set you up with a proper Asian adventure! Lot less yaks now, but still plenty of almost untouched places. A couple of us are hoping to pull off the first motorcycle trip up to Kel Suu next summer as well.

When i saw the first pictures i thought that too, gasoline or kerosene added to diesel, but I thought due to a mistake, not on purpose.

312d said:

When i saw the first pictures i thought that too, gasoline or kerosene added to diesel, but I thought due to a mistake, not on purpose.

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Let me make sure the record stays straight...I have never and will never intentionally add gasoline to diesel. If it was in this tank then it was a mistake, either by client or by fuel station.

I was told that if you have petrol in your diesel tank, for whatever reason, to add two stroke oil to compensate.

kyrgyznomad said:

Let me make sure the record stays straight...I have never and will never intentionally add gasoline to diesel. If it was in this tank then it was a mistake, either by client or by fuel station.

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Take a sniff at the fuel fill neck. I was able to smell petrol in diesel down to about 1.5% concentration. If you smell it at all then that may help to explain things.

Thunderbolt said:

I was told that if you have petrol in your diesel tank, for whatever reason, to add two stroke oil to compensate.

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From what I have gleaned, to some extent that is true to help with lubricity. Once you're past about 5% gas (petrol) concentration then draining the contaminated fuel and purging is the safest action.

There is some info and data in my story here.

https://sprinter-source.com/forums/showthread.php?t=15652

vic

Ok, after an informative sidetrack into whether or not it received gasoline, we have taken the motor to several engine builders. Everyone has immediately pointed to overheating. Which it did some month before. Further, they think that the scored cylinder walls were the first damage, followed by metal chipping away the pistons, etc. Not sure entirely, but the mechanic who broke the belt then rigged another that bypassed the power steering pump and upper heater water pump (which he claimed was just A/C) should not really be in business.

Question for the day. If done right and the cylinders are bored 0.5 mm over, is a rebuild just as good as a used motor of semi-unknown history? Can a motor recover from this and have a good, long, usable life?

Yes as long as it hasn't taken a twist block that is!

What I find is that #2 bearing cap for some reason has a habit of being too loose in the block register when there has been a serious overheat or seizure.

In many cases I have recovered it by taking a "gash" cap from a wrecked block and employed it in #2 position when the block register will hold the cap nice and tight/snug. Then torque it all down to 40 lbf ft plus a 90 degree torque to yield then line bore it .

Once all finsihed and cleaned up drop the crank in use plastigauge to check the running clearances. Then check to see if the crank spins without any bind in the crank tunnel which if all goes well it should!
Best of luck
Dennis

lindenengineering said:

Yes as long as it hasn't taken a twist block that is!

What I find is that #2 bearing cap for some reason has a habit of being too loose in the block register when there has been a serious overheat or seizure.

In many cases I have recovered it by taking a "gash" cap from a wrecked block and employed it in #2 position when the block register will hold the cap nice and tight/snug. Then torque it all down to 40 lbf ft plus a 90 degree torque to yield then line bore it .

Once all finsihed and cleaned up drop the crank in use plastigauge to check the running clearances. Then check to see if the crank spins without any bind in the crank tunnel which if all goes well it should!
Best of luck
Dennis

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Planning to let a local engine builder do it. Part of me wants to do it, but I don't have the right shop (I have only a roof over a two car parking area, no proper garage and last night it was minus 13 Celsius) plus I don't know the right guys to do the machining.

I'm going to check up on him a lot and check that he does what you mentioned. As far as the bearing cap, he said today, "90% of the time when these engines overheat you need to replace the bearing caps." Actually he said the word in Russian and neither I nor my driver knew it, so he had to show me. Part of the reason I like this guy, he's the only one we've talked to who has said exactly what he'll do, step by step, and has taken the time to make sure we understand. He also has a properly equipped and clean shop, so that's a plus!

This is my first full engine rebuild, so maybe I have some dumb questions. What's the deal with different sized bearing caps. Does the crank sometimes need to be machined as well?

Looking at using Nural pistons, is there anything I need to know?

kyrgyznomad said:

Planning to let a local engine builder do it.


This is my first full engine rebuild, so maybe I have some dumb questions. What's the deal with different sized bearing caps. Does the crank sometimes need to be machined as well?

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well that is not a dumb question, in fact that IS THE question for an engine builder.
In principle the crankshaft should not be machined unless it is damaged, a polish might help to not remachine it, but if it is scored badly that will affect oil pressure and probably disturb the hydraulic wedge to get the crankshaft floating.
in the 611.983 and 612.983 engines:
crankshaft radial play is 0,03mm -0 ,05mm for a new one, and wear limit is 0,08 mm. maximum crankshaft excentricity is 0,16 mm supported on the ends.
bearing codes are at the tip of the crankshaft (for that individual crankshaft only) and are:
blue=B 2,255 - 2,260 mm,
yellow=G, 2,260 - 2,265 mm
red=R, 2,265 - 2,270 mm
white =W 2,270 - 2,275 mm
and violet=V 2, 275 - 2,280 mm
all this measures are for a new crankshaft with standard measure.
When you remachine a crankshaft, then comes into play a new set of bearing shells up to four repairs and they all again coded with colors, starting from 2,375 mm and so on.
so you need a micrometer with at least 0,005 mm resolution. ( the more resolution, the more expensive tool).
I posted this engine manual time ago there is more, but I don't even know if this correspond to your engine model.

kyrgyznomad said:

Planning to let a local engine builder do it. Part of me wants to do it, but I don't have the right shop (I have only a roof over a two car parking area, no proper garage and last night it was minus 13 Celsius) plus I don't know the right guys to do the machining.

I'm going to check up on him a lot and check that he does what you mentioned. As far as the bearing cap, he said today, "90% of the time when these engines overheat you need to replace the bearing caps." Actually he said the word in Russian and neither I nor my driver knew it, so he had to show me. Part of the reason I like this guy, he's the only one we've talked to who has said exactly what he'll do, step by step, and has taken the time to make sure we understand. He also has a properly equipped and clean shop, so that's a plus!

This is my first full engine rebuild, so maybe I have some dumb questions. What's the deal with different sized bearing caps. Does the crank sometimes need to be machined as well?

Looking at using Nural pistons, is there anything I need to know?

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Just a few additional comments on your post.
Having worked on a few Russian engines myself no doubt he's probably familiar with the fact that their manufacturing has difficulty holding tolerances.
The Mercedes product is exactly the opposite, with adherence to tolerance specs, it is one of the products fortes. Consequentially when you work on one to rebuild it the same level of tolerance will be present like crank tunnel alignment and cap "fit". In most cases any structural deviation like the looseness of #2 main bearing cap caused by distortion which I have found on several engines might be discovered. This may dictate you needing an odd cap from an old engine which will require re-machining into place since main bearing caps are matched to each individual block.

These factors are the first things I take into account after the block has been cleaned, de-greased and readied for examination.

As a side bar for info; the rod caps are individually split (common practice these days) so they cannot be mixed up nor interchanged without affecting running clearances.

I have no experience of using Noral pistons I only use Mahle. However here are two distinct builds when it comes to pistons and rods so beware!
Essentially early rods had a small end which was concentric in shape.
Later rods are tapered or reduced at the top. Consequentially the piston where its is mounted onto the wrist or (gudgeon pin as it is sometimes called ) is shaped accordingly and they are not interchangeable. Consequently you have to specify what rods you have on your engine build to get the right pistons.

Normally the dealer will specify a set of pistons or rods for that matter appropriate from build records per Vin/engine block number. Buying in the aftermarket will have none of those checks and balances so beware!
Best of luck and stay warm
Cheers Dennis