BMP exhibits shaking behavior in partial load range / Dominant cylinder

Last edited on 14-02-2012, 15:23, edited 3 times in total.

Hello everyone

I have a problem with the engine in my Passat, MKB BMP, and would appreciate your assistance...

If the engine is only partially warm, the coolant is 30 - 80°C and the oil is 40 - 70°C, and I release the clutch in neutral, I hear a noise coming from one cylinder that reminds me strongly of an old, long-stroke single-cylinder boat diesel

... "knonk knonk knonk"...
When the engine is properly warm and at room temperature, the noise is not present.

The warm engine is not running smoothly and is shaking, especially at partial load (on the highway at between 2000 and 3000 RPM). He walks quite calmly, even when I ask him to perform.
At speeds of 1800 RPM during acceleration (full throttle), it sounds rough, and you can easily feel a slight vibration.

I have performed 3 tests using MWB 1, 13 and 23 with cold, lukewarm, and warm engines. Based on the logs, I believe we can exclude the PDs.
Please correct me if I am wrong...

Would it be beneficial to examine the tandem pump in more detail?

Does anyone have any ideas on how I can best continue my search?

LG Jan

Hello,

The logs appear to be normal. I would almost rule out problems with the injection system.

First, it should be checked whether the noise is caused by a mechanical cause (e.g., a hydraulic shock), or whether the seal is not completely sealing the exhaust valve in a cylinder.

Best regards, Rainer

Could ZMS not be a potential cause of these symptoms?

Piston rod?

Last edited on 15-02-2012, 18:20, edited 3 times in total.

Thank you for your responses!

I tried to pinpoint the exact location of the noise tonight. As it appears, the noise is actually coming from the cam shaft area, as Rainer had already suspected.
Unfortunately, I could only listen without any load, I was alone.
What, however, is a bit puzzling, is that the noise is dependent on the load...
I hope that Deus Violentia's theory about connecting connecting rods or piston rings does not come true...

I'm going to remove the VD tomorrow.

@ dieselmartin, my ZMS does make some rattling noises at idle, even when the engine is cold, but the "slider test" from this forum passed...
Does it still apply??

LG Jan

Last edited on 17-02-2012, 1:20, edited 1 time in total.

Hello,
Today I checked the hydros. In my opinion, they seem okay; I was able to press them down to an estimated 0.2 - 0.4 mm.

The problem has worsened (over the last 200km) above 1600 U/min.
Shake the box as long as the gas is being injected, the more gas I give, the more pronounced the shaking will be. In normal operation, it runs quietly.

The knocking sound (which sounds like it could be propeller bearings or piston rod bolts to me) hasn't gotten any louder, but it's now also noticeable when driving in a low gear (maneuvering with a higher RPM than when idling), but not always.
It occurred to me today when the engine was warm, having been idling for about 15 minutes. When I started driving afterwards. After 5 minutes of driving, it was quiet again.

Would it be a good idea to measure the oil pressure? These engines, as I've read, sometimes have problems with the oil pump's operation. However, I've never received any warning messages about oil pressure. I don't know how reliable this display is. When the oil pressure switch is disconnected in idle, the display shows nothing! She doesn't really get involved until things start to heat up...

I don't know how to proceed... What would you do next?

Head? Replace ZMS?

How can the piston ring clearance and the connecting rod bearing be checked most easily?

LG Jan

Last edited on 17-02-2012, 1:56, edited 1 time in total.

Quote:

However, what's a bit puzzling is that the noise is dependent on the load...

That's usually not good.

It should actually come from the engine block, not the ZK.

The valve train doesn't notice whether it's being injected or not, or whether it's being accelerated, unless a PD (positive displacement pump) malfunctions or fails. After looking at the logs, it doesn't seem that way.

If it's the propeller shaft bearing, the noise should actually get louder as the temperature increases. At the Pleuelauge =?

To do this reliably, you must at least remove the oil pan and the crankcase oil level sensor module before you can access the bearings.

PS.: Previously, we first looked for the culprit using "cylinder shutdown".
So, one by one, each cylinder was taken out of service. If the noise is gone - defective cylinder found.

How many miles does the vehicle have on it?

Last edited on 17-02-2012, 10:52, edited 1 time in total.

Quote:

How many kilometers does the vehicle have on it?

The vehicle has 115,000 km and I purchased it from a private seller at 109,000 km (of course, without warranty). I'm starting to feel like I've been pretty badly ripped off with this purchase....

I will take out the oil pan and the balance wave module tonight, and I will also check the condition of the oil pump drive at the same time...

Best regards, Jan

PS. Does the engine actually have another OT marking besides the one that can only be seen with the KW-Stop?

Last edited on 19-02-2012, 1:13, edited 1 time in total.

I have now completely disassembled and inspected all the connecting rod bearings, and they are all in good condition... as are the tappet pin of the oil pump and the internal hexagon on the balance shaft module. I was also unable to detect any play in the connecting rod bolts. The design of the balancing wave module's head seems fine to me.

Found a small brass sleeve in the oil pan, which clearly had some kind of "physical altercation" with another engine part...

Where do you think it came from??
Does anyone have any ideas?

LG Jan

Last edited on 19-02-2012, 0:39, edited 2 times in total.

Hypothesis: Is the swing arm pivot point jammed, or is the camshaft faulty?
EDIT: I think the pivot axle pins weren't so brass-colored, but silver and made of aluminum or steel. Furthermore, it is questionable whether the removed plugs would have actually made their way into the oil pan.
But it would perfectly fit the actual problem.

Last edited on 19-02-2012, 18:52, edited 1 time in total.

Quote:

Hypothesis: Sticking of the rocker arm pivot, or camshaft failure?

You are right, the pivot axle bushings are made of aluminum, and unfortunately, they are all in the correct position. That would have been nice. Thank you for your tip.
What do you mean by "camshaft failure"? I only have one continuous camshaft. On one side, it is driven by the ZR, and on the other side, it is closed and drives the tandem pump.

I could imagine that the brass piece might be an electrical contact from the PDE cable.

However, since my entire cable bundle is complete, I can't imagine how it got in there.

What do you think I should do next? Could the error be caused by a faulty valve, or a crack in the ZK?
I would be surprised, given the low mileage and the fact that the vehicle (to my knowledge) had never been "tuned".
I read in this forum that 2-valve engines are less prone to ZK (crankshaft) cracks.

I am very grateful for every hint... Since I'm running out of ideas...

Best regards, Jan

Last edited on 26-03-2012, 23:16, edited 2 times in total.

Replaced the ZMS last weekend on suspicion, and the result is: The rattling noise when starting the engine is gone. The vibrations in the partial load range are still present.

Feels a bit like a poorly balanced bicycle, just with engine RPM...
When I release the clutch, it's quiet.

I've noticed that when I press the clutch pedal so that it touches the release lever, I can clearly feel the vibrations in the pedal. When the clutch is fully depressed, I feel nothing. The vibrations are very noticeable throughout the entire speed range.

Measured the oil pressure at 75°C oil temperature at idle, 2 bar, and at 2000 rpm, 4.2 bar.
what looks good for me.

How to proceed... I wonder... and you...

LG

Last edited on 27-03-2012, 11:36, edited 1 time in total.

Quote:

I've noticed that when I press the clutch so that the release lever touches, I can clearly feel the vibrations in the pedal. When the clutch is fully depressed, I feel nothing.

My AHF in the A3 8L also did this, with the approximately 270,000 km that I had the car for. "Broken" there was nothing.

I'm more inclined to think that this piece of brass is quite interesting, but I can't immediately think of where it might have come from. Piston-bottom cooling nozzle sprays?

Maybe record the sound?

Best regards, Rainer

Cause found... The crankshaft has 0.7mm of axial play, and the first crankshaft bearing is worn (bearing shells and crankshaft). The tires can be felt clearly with a fingernail on the crankshaft.
The remaining parts are in good condition. The starting disc in Lager 3, which is closer to the steering side, looks okay from the surface, but it is so worn that the "oil channels" are only about 1/10mm deep. The polished surfaces of the KW, which come into contact with the contact discs, have very few visible wear marks.

Where does this come from? And why does the starting disc on the left side show more wear? The force of the clutch spring would therefore be exerted on the other...

But that still doesn't explain the find, has Rainer investigated the possibility of a piston-cylinder cooling system?

Last edited on 27-03-2012, 9:24, edited 1 time in total.

Unfortunately, I also have no explanation for the find... Yes, the oil-spraying nozzles are okay.
LG