OM617 knocking - PeachParts Mercedes-Benz Forum

Tomas.brannholm · #1 10-25-2015, 05:13 AM

Hi all,
New member from Sweden with a problem.

I have a 300SD with approx 170 k miles, full service history and only two owners.

I have a knocking sound from the engine (not super loud), the sound is louder on turbo side and I experiencing the knock is louder when hot.
The engine is shaking a bit and "puffing" sound from the exhaust. No smoke and oil pressure is stabile warm on 30.
When I crack the injector lines the knock decreases when I come to cylinder 5. I have tried to move injectors and delivery valve and the sound stays at cylinder 5.
When feeling on injector hard lines the pulse is stronger to cylinder 5 and 3.
Cold and warm start is very quick.
No babbitt or other metal in oil pan or filter.

This is new on the engine:
New balanced injectors
New timing chain
Valve adjustment done three times
Diesel purge and new filters
New oil and filter
New exhaust gasket
Compression check (cold):
1 = 320
2 = 330
4 = 330
5 = 330
3 = 320

Hot
1 = 370
2 = 365
4 = 370
5 = 375
3 = 365

Can it be the IP or cylinder head (valve)?
I am really afraid that it is a bearing or pin and a rebuild is necessary.

I would appreciate all help I can get to make the right decision.

// Tomas

https://www.youtube.com/watch?v=A28iaHoWUS0

leathermang · #2 10-25-2015, 10:17 AM

Before going any further...... I suggest a hot compression test....
The puffing from the exhaust and the ability to affect the noise by taking away the fuel to number five would seem to be important to me at this stage of investigation.

Tomas.brannholm · #3 10-25-2015, 10:38 AM

Quote:

Originally Posted by leathermang

Before going any further...... I suggest a hot compression test....
The puffing from the exhaust and the ability to affect the noise by taking away the fuel to number five would seem to be important to me at this stage of investigation.

Check your pm's....

Hi,
I will do compression check hot and post the value here

// Tomas

barry12345 · #4 10-25-2015, 12:23 PM

Like those even cold compression numbers.

The way I would tackle this is to find out the operating temperatures of say number one cylinder and number five. Or do them all properly.

In the archives there is a long thread on milli volt testing. This is a way to examine the comparison of the running temperatures in each cylinder.

You will have to do the test properly by moving glow plugs. If the number five glow plug has a higher voltage than any other cylinder chances are your injection pump is out of calibration. If they are all the same more than likely it is mechanical in nature.

This has been successfully used to semi recalibrate one cylinder if it is indicated as needed. Your knock could be one over advanced element.

Personally I would not adjust that element without a milli volt indication that it was probably off. Plus the milli volt method allows you to get it closer to what it should be if it is off.

Judging by your first post you are a good candidate to do this properly.. Also welcome aboard to the most helpful site in my opinion for these cars.

You can even do a preliminary scan at the glow plug harness connector. Meaningless basically without using glow plug standards yet if the temperature variation is extreme it might still indicate it is worth pursuing.

This test is best done with a set of newer glow plugs but is still accurately doable by moving glow plugs. Or buy one new plug to move around. I stopped talking about this test quite some time ago. People where taking short cuts.

The glow plug is just functioning as a thermocouple for you.The negative of the meter must use the engine. Not at the negative post of the battery or body.

I have a feeling that you probably own a meter with a milli volt scale. Just read the voltages at the removable glow plug harness. Record and post them on your thread. probably will be in the 5-10mv range.

Only takes a minute or two once the engine has warmed up. If say number 1234&6 are indicating a pretty similar voltage. Yet number five is several milli volts higher it is worth pursuing more accurately. If 1234&6 are all over the place it only indicates the glow plugs have aged and are no longer good enough for accurate comparisons. Then you have to go to using a standard plug for each cylinder. This can be done using one of the existing glow plugs. Or one new one.

Sorry about the long post. Still it is the cheapest do it yourself approach to separate and sometimes repair some issues to my knowledge.

These engines are also somewhat noisy by nature. So it is hard to get a clear ideal from your video. Probably just me.

Tomas.brannholm · #5 10-25-2015, 12:48 PM

Hi Barry,
If I understand you correct I will use one glow plug for measuring temperature in the cylinders (1-5)?

I was checking the car today and when cold it is almost now knocking also the engine temperature is very stabile just above 175.
The turbo have new sealing's and bearings
I just give some more information about the condition of the car.

Thanks.

// Tomas

leathermang · #6 10-25-2015, 01:48 PM

Barry's wild imagination is at work again. No physical or theoretical basis EVEN if some difference in temperature were found...to imply a cause to the problem presented.

The idea that the glow plug hole... protected from the actual combustion chamber activities by the restricted access through the tiny radial holes in the pre combustion chamber ... might could read some difference in temperature in the combustion chamber given the averaging effect of the shared engine coolant around the sleeves...and the mass of the head...
and that difference might be enough to cause this noise is not supported.... and if it WAS.... it would still point to a defective dispersal of the fuel into the combustion chamber... all of which... given the new injectors...
points to a need to examine and make sure the tiny radial holes of the precombustion chamber are clean.

At this point is where Funola will attack me for what is just sharing the information in the FSM .... even though my recommendations for the rate of checking these very important holes are very conservative...
either once every 100,000 miles OR if some symptoms exist that point to uneven power being produced from different cylinders after all the easy fixes like replacing injectors are exhausted....

cooljjay · #7 10-25-2015, 02:36 PM

Quote:

Originally Posted by leathermang

Barry's wild imagination

Sounds like a theme park ride

leathermang · #8 10-25-2015, 02:59 PM

I think he could make a lot of money writing fiction... once he gets hold of something he is tenacious ....

Diesel911 · #9 10-25-2015, 04:24 PM

You did not say if you bought this car and drove it for a while with no knocking issue or you just bought the car and it came with the knocking issue.

If you just bought the car and it came with the knocking issue does it look like one or both of the Oil Cooler Hoses was changed recentely. That might indciate an Oil Cooler hose blew and there was a sudden loss of Oil Pressure that could have damaged the Engine.

If the Engine was overheated you can also ruin Rod Bearings (that happend to my Van needed a new Rod and Crankshaft from that issue). You would not know if the Engine was overheated unless the prior owner told you.

On gasoline engines if you run the engine without a spark plug wire and the knock goes away it was considerd a Con Rod or Piston Pin bearing issue.
http://www.ehow.com/info_12229282_removing-spark-plug-wire-make-rod-knock-away.html

That is similar to cutting the fuel off to one Injector by lossening the line nut. And, since you swapped the Injectors and the sound stayed on #5 you have verified the problem is not the Injector itself.

Unfotrunatly because a knock can also be created by the Fuel buring in the Engine not burning correctly in the cylinder that does not entirly rule out some other issue with the Fuel. Timng, Air gettng in the system and or low Fuel Supply Pressure.

Check and see if the Ball Pin inside of the Precombustion chamber is still intact and if it is loose.
Also does the inside of the #5 look the same as the others. Meaning is the carbon buildup the same and how does the carbon look. Their sould be an even balck coating of non-reflective dry carbon on the inside. If the carbon is shiny and wet looking you are some how getting Oil into the precombustion chamber.

Comment on one cylinder going bad. The Turbo Engines have Oil Spray Nozzles that spray Oil up under the Pistons. If somthing that prevented the Nozzle from spraying the oil properly the Piston would not get cooled properly and that would have an effect on the Piston Pin and Bearing there.

You might drain out the Oil into a really clean container and remove the small steel Oil pan and inspect it for metal particles. Check the bottom of the Pan you drained the Oil into.

I have compression that is too low on #5 of my 1984 300D and there is a Fuel Knock on that Cylinder till the Engine is about 1/2 warmed up but there is nothing that sounds like a Rod or Piston Pin Knock.

This may or may not help diagnose a Con Rod bearing knock. Drain out the existin Oil and fill it with single grade 40 weight Oil. Start the Engine and see if the knocking sound has decreased. Then see if as the Oil gets hot if the sound increases.
The thick cold oil may cushion the blow of a bad rod bearing and reduce the sound till the Oil gets hot.

leathermang · #10 10-25-2015, 04:36 PM

Quote:

Originally Posted by Diesel911

.....Unfortunately because a knock can also be created by the Fuel burning in the Engine not burning correctly in the cylinder that does not entirely rule out some other issue with the Fuel. Timing, Air getting in the system and or low Fuel Supply Pressure ....

Also a possibility is blocked radial holes in the bottom of the pre combustion chamber.

Tomas.brannholm · #11 10-25-2015, 04:47 PM

Hi,
I bought the car with the knock and it is only one owner before me. The service records is more then full and only on Mercedes workshops. The car is in super condition and AC, power windows etc is working. No new hoses for the oil cooler.

The problem is the knockind sound.

I have checked the oil pan and filter no babbitt or other metall.

I have checked the ball in the chambers and all ok, I will pull the chembers for inspection and cleaning. Part of the inspection will be inspection inside the cylinder with a boroscope. For reassembly I will put new collar nuts and selings.

Is it more checks I can do?

Thanks,

// Tomas.

83TD · #12 10-25-2015, 05:10 PM

When my 1983 300TD was still relatively new and under MB warranty it developed a knocking sound which sounded to me like a bad crank bearing. I took it to the dealership which had two senior mechanics who, at the time, worked almost exclusively on diesels, and they both assured me that it was not a crank bearing. They insisted that I watch(try that today) as they loosened the lines on the injectors one by one until the sound went away, removed that injector, disassembled it, and cleaned it up with some fine emery paper. Put it back together and no more knocking sound. They said that it was hanging up.

So it may be something really simple.

Peter

leathermang · #13 10-25-2015, 05:52 PM

By ' hanging up ' did they mean not enough fuel or too much ?
or that it affected the timing of the fuel input ?

Diesel911 · #14 10-25-2015, 10:26 PM

Quote:

Originally Posted by Tomas.brannholm

Hi,
I bought the car with the knock and it is only one owner before me. The service records is more then full and only on Mercedes workshops. The car is in super condition and AC, power windows etc is working. No new hoses for the oil cooler.

The problem is the knockind sound.

I have checked the oil pan and filter no babbitt or other metall.

I have checked the ball in the chambers and all ok, I will pull the chembers for inspection and cleaning. Part of the inspection will be inspection inside the cylinder with a boroscope. For reassembly I will put new collar nuts and selings.

Is it more checks I can do?

Thanks,

// Tomas.

If you use the correct tool to remove the Prechamber Retainer Rings they can be reused.
There is Alumnum Crush Rings between the Prechamer and the Cylinder Head and there is also a hefty torque on the Retaining Rings.

Diesel911 · #15 10-25-2015, 10:36 PM

Quote:

Originally Posted by leathermang

By ' hanging up ' did they mean not enough fuel or too much ?
or that it affected the timing of the fuel input ?

I am sure he is speaking of the Pintel/Needle in the Injector Nozzle.

Where I worked we used to put the Injector Pintel in a tiny Cuck that was on a Electric Motor.

We put 1200 Grit compund on some folded Toilet Tissue and polished only the lenth of the Injector Nozzle Pintel where it slides in the bore of the Injector Nozzle.

Stay away from the tip of the Pintel and the seating area right behind the tip.

Even though it is under spring pressure if the sides of the Pintel get rough it will slow the return of the Pintel and it effects the Atomization.

But, the Original Poster said that he swapped the Positons of the Injectors and the sound remained in #5. I think he also said the Injectors were rebuilt with new Injector Nozzles.