Heavy engine noise

[Schulmann]

Tuesday I was driving on the highway and I decided to accelerate. I revd to engine to 5000rpm and wanted to change speed when the engine began this very heavy noise.

It sounded like a broken connecting rode or a broken rocker arm. It wasn't sounding like a regular valve noise. The noise was heavy and very strong. Right away I decided to have the car towed to Dodge.

After having analyzed the situation we managed to isolate the noise:
- It was around cylinder #7 but the noise was too strong to really say what's wrong
- The noise was stronger on the oil pan, it sounded like coming from below (broken connecting rod ?)
- In addition the spark plug was broken on cylinder #7.

We checked compression and looked good.
Checked rockers and looked good.

Finally my dealer decided to put some oil cleaning staff in the engine and the NOISE DISAPPEARED !!! I have to say that my car was running rich before because of a trouble with my PCM.

Do you have an idea what was wrong or what might still be wrong on the car ?

NB: No mods on the car just the standard staffs !

 

[Ulysses]

Usually when the connecting rod breaks loose, there is a very loud clanking noise as the rod slaps up against the block and right away, you know it's a broken or separated rod. The broken spark plug is a definite clue as this would cause the engine to lose power, sound like the engine is missing and the engine would shake a bit as it struggled.

The question is, was the noise still there after replacing the spark plug?

What's a bit of a mystery is why the sound would go away after putting in oil cleaning stuff.

 

[Sean Roe]

When you said the spark plug was broken, what do you exactly mean?
Did the insulator break, parts missing?
If so, maybe they were in the cylinder while it was running, but then blew out the exhaust?
Picture available?
On the good news side, at least the compression was ok. Glad to hear it ran properly after replacing the PCM.
Regards,
Sean

 

[Schulmann]

I will post later a pic on the spark plug.
The plug looks like it was hit by something (cylinder head). There is no space left between the tip and the electrode. A small part of the insulation is also missing.

The bad new is that my dealer kept the car for the Thursday for test rides and the noice came back. He put again some cleaning staff into the cylinders on the advise of Chrysler.
Chrysler told them that it must be some heavy carbon deposit. My car has only 6000mi .... and is still on the basic warranty.

The worst it that it all happened before VOI 8.
The good thing is that it happened in Montreal and not somewhere in Kentucky ...

 

[Mike Adams]

You should pull the plug in that cylinder and using a pencil light and look in to see if anthing is embedded in the piston. Which plugs are in you car the factory ones or the bosch

 

[newredrt10]

He put again some cleaning staff into the cylinders on the advise of Chrysler.
Chrysler told them that it must be some heavy carbon deposit. My car has only 6000mi .... and is still on the basic warranty.

This seem DC quote of the month. My wifes min van is knocking and this is what the dealer said. While getting the van done some one with a M300 was in for the same thing. DC must have stock in the cleaner company

 

[Schulmann]

I think one of the top piston rings is broken and went out by the exhauste. I have found small metallic parts in the exhauste just before high flow cats.

 

[Schulmann]

 

[JDR]

So the noise was the piston "trash-compacting" the parts against the head until they were small enough to blast past the exhaust value? Ouch.

 

[Tom F&L GoR]

OEMs have certain engines with tight piston top to head clearances. When enough deposit (from running rich, consuming oil, or certain gasolines) builds up, the deposit on the piston top or head collide. What is interesting is that when the engine warms up, this noise goes away because the clearances change. If this occurs, dealerships assume it's a deposit issue and rather than disassemble the engine, are using fuel additives or top end additives to remove the deposits and eliminate the noise.

I wasn't aware that a V-10 was one of these cases; certain Japanese and (I think) the 3.3L Dodge were prone to this. Given the low level of cleaning additives in gasolines, it's probably a little beyond the "rare" stage.