Dröhnklappern im Leerlauf bei rollendem Wagen | Posts 16+

Roger wrote:

I just saw it, but what about the influence of the AGR? It also causes a change in sound. My ASZ engine in my Golf has exactly the effect you described, practically from the beginning, and I've always attributed it to the EGR system so far.

Aah, so I'm not alone after all *lol*.

What's the mileage on your car so far? Has the noise gotten worse over time for you?

It can't be the AGR (Abgasrückführung), because it's not working properly (sometimes), and yet the noise is still there...
But what kind of noise change does your EGR cause?

I just got the socket wrench for the transmission oil drain plug.
Hopefully, tomorrow I can drive the car into a pit and check the oil level.

A (former) VAG master with a private workshop here once told me that, according to his research, the oil drain plugs must not be opened, otherwise the warranty would be void .

Can someone comment on this?
My screws, at least, don't have any visible seals or anything like that.

Currently, it has 30,400 kilometers on the odometer.

The sound is exactly as you described it: a constant noise while driving, then alternating with brief periods of silence during the first few seconds at a red light. Then, after a maximum of about 20 seconds, it disappears. Pressing the clutch pedal or giving it short bursts of acceleration doesn't change anything.

It hasn't changed significantly over time, but it always appears after driving a few hundred meters, and not when the engine is completely cold.

"If this isn't coming from the EGR valve, then my EGR valve is largely 'silent' – at least, I haven't noticed anything else. However, it has been active since the very first kilometer, and there's nothing significant built up in the intake manifold. Everything looks clean there, at least as far as I can see through the removed pressure hose that passes through the EGR valve."

Roger wrote:

The sound is exactly as you described it, so it's constant while driving, and then alternates and stops for the first few seconds when stopped at a traffic light.

Hi Roger,
Then there are differences: mine only makes a rumbling noise (alternating) as long as it's rolling, and it's most noticeable between approximately 10 and 0.1 km/h.
The rest of your description is accurate, and this also applies:

Quote:

However, it only occurs after driving for a few hundred meters, not when the engine is completely cold.

Does it also turn off automatically after about 20 seconds of idling for you?

If it makes you feel better, I just rented a car (a Passat 96 kW TDI, the latest model with the turn signals in the mirrors). And it makes a very similar noise when idling, only it's much better insulated and it remains completely constant.

While driving, it emits a very deep rumble, even with the lowest load in 1st-3rd gear, between 1,400 and 2,000/min, which can almost cause headaches. Fortunately, the diesel knocking is well-dampened. And it has extremely short gearing; 2,000/min in 6th gear is only about 100 km/h.

Roger wrote:

Does it also turn off for you, at the latest, after about 20 seconds of idling?

Hm, maintaining a speed between 10 and 0 km/h for 20 seconds straight suggests a space issue or a traffic situation – I haven't tried that yet.
As I said, as soon as mine is fully charged, it's like it's turned off.

Quote:

If it comforts you, I just rented a car (a Passat 96 kW TDI, the newest model with the turn signals in the mirrors). And the noise at idle is very similar, only much better insulated, and it remains completely constant.

The first common response to transmission noise is often "free wheeling." However, this noise usually disappears when the clutch is engaged. Does this apply to the Passat?

No, as before, pressing the clutch pedal in the Passat doesn't change anything. Except perhaps that it deactivates the jerk dampening system...

Okay, I checked the transmission fluid level today.

Possibly, there was a slight gap between the bottom edge of the sighting hole and the surface – unfortunately, the depression was slightly tilted, which made it impossible to check the measurement accurately.

I ordered 1 liter of oil and will top it up soon, but I'll check the level more precisely beforehand using a jack (to compensate for the tilt) and a level.

What bad things can actually happen if there is too much oil in the transmission? And at what percentage of overfilling does it start to happen (if at all)?


My current theory about what's going on is roughly this:
The rattling parts are located approximately at the level of the normal oil level.
When the vehicle is moving, oil is pumped up from the "sump" -> the loose parts are exposed and can rattle (when there is no flow of force).

If you stop, the oil flows back down and dampens the rattling. In my gearbox, it happens as soon as the car comes to a stop; in Roger's, it takes a little longer, after some extra oil has dripped and seeped down.

If that's correct, the rattling should be influenced by the amount of oil: adding a little more might (partially) reduce the noise.

It's not exactly "logical," but it's the best I could come up with so far...

What bad things can happen if there is too much oil in the transmission? And at what percentage of overfilling does it start to happen (if at all)?


Normally, it's not possible because the maximum fill level is at the bottom edge of the filling opening. Anything you add beyond that will immediately spill out.

Depending on the transmission, if too much fluid is added, it slightly increases the running resistance of the transmission. However, this is usually negligible. I have occasionally heard of minor shifting problems when the transmission is fully warmed up, but I would like to point out that these problems could potentially be caused by other factors.
The situation becomes more critical with automatic transmissions, as the pressure in the torque converter can become significantly too high.

Julian wrote:

ulf wrote: What bad things can actually happen if there is too much oil in the transmission? And at what percentage of overfilling does it happen (if at all)? Normally, this is not possible because the maximum level is at the bottom edge of the filling opening. Anything you add beyond that will immediately flow out.

Yes, but only if the car is perfectly level.

While on the uneven ground, I can hold a level horizontally under the driver's seat and use a jack to compensate for the tilt.

But which indicator line on the carriage shows that it is not positioned on an uphill or downhill slope?
As soon as it's angled uphill, "too much" oil flows in without leaking out.

Hello Ulf!

I think you shouldn't worry too much about a slightly too-high transmission fluid level.
I performed the transmission fluid change using ramps, and I also filled the fresh transmission fluid while the car was at that angle. Therefore, I'm certain that there's slightly more oil in the transmission than there normally should be. Oil starvation is much worse than having a few milliliters too much.
The only potential negative effect could be that, on longer highway stretches at high speed, the warming of the transmission increases due to the increased parasitic losses. However, I don't see this as particularly critical, as even with a significant overfill, you can probably add 100-200 ml. Worse would be if you completely fill the transmission to the very top with oil, as this would dramatically increase the viscous friction in the transmission. But who would do that ?

Regards,
Alex.

Hello,

I once added about 0.1 liters of fluid, just to be on the safe side, through a vent opening next to the shift shaft.

The gearbox is "more than full" with it.
When the vehicle is parked on a slightly inclined surface in the pit (as indicated by a level), with no side tilt, oil leaks out as soon as I remove the dipstick.

Only the droning sound remains practically unchanged .
(but sometimes it seems to me that it can be shifted into a lower gear even more easily).