Annoying Rumble: Causes and Solutions

Hello.

My Golf (current mileage: 19,500 km) has become noticeably louder inside the cabin over the past approximately 1,000 km.
The engine is louder (and has a more robust sound).
In addition, it makes a louder rumbling noise at lower RPMs than before (approximately 1250-1800 RPM). The sound is almost like the old dial-up modem tone (~400Hz). This noise is only audible in idle mode.
Who knows a solution?

Best regards, Juan.

Hello,

It might be related to the transmission. You could try adding some transmission fluid; the standard oil level in my A3 was lower than it should have been, even though there was no leak.
This at least reduces the noise somewhat. Gear noise can sometimes originate from gear teeth that are not 100% optimally shaped.
For example, in my car, the engine makes a noise in the fourth gear when I give it just a little bit of gas (basically, when I'm almost coasting and maintaining a speed of around 50 km/h).
I've driven several TDIs (some of which were practically new) that make slight transmission noises when accelerating, and perhaps Michael II knows more about this.
Since I've experienced similar noises with other vehicles before, I consider this issue to be unpleasant but not critical.
Regarding the "rougher" engine noise: engine mount wear is very unlikely given your low mileage. Check if your exhaust has any cracks or if it's hitting somewhere.

Best regards, Rainer.

Thank you for the tips. After thinking about it for a while, I realized something else: before the aforementioned 1000 km, the engine noise gradually became louder, coming from the passenger side, roughly in the area of the glove compartment. My suspicion is that some clamp or hose connection has come loose. By the way, the engine code is ALH. Previously (i.e., up to 15,000 km), you could also hear the turbocharger, albeit quietly, with that hissing sound. This sound has now been completely masked by the rumbling. Perhaps we can narrow down the problem...

Thank you again.
Regards, Juan.

P.S.: Regarding quality: I managed to reach 190,000 km with my driving school TDI (1Z, 3/96) without any major issues, except for the water pump, which is not bad considering the somewhat higher stress it was subjected to (especially the clutch and frequent stalling).

Okay, the rumbling noise is gone now, and the engine sounds like it used to. Adjusting the engine mounts, as MichaelII recently described, turned out to be the solution.
Here's another question: At what speed do you shift your 66kW TDI engines (preferably ALH in a Golf) into the next higher gear? My old 1Z couldn't run at 50 km/h in fourth gear; it would shake and roar like crazy. The ALH engine does much better, and it shifts into fifth gear around 65 km/h.

Best regards, Juan.

Hello Juan,
I can confidently drive my 1Z at 50 km/h in 4th gear (5th gear only downhill with a slight tailwind ).
Switching threshold is typically between 2000 and 2500 /min.
The 90 horsepower G4 (likely an ALH model) that I once had as a loaner car...
it could be switched just like that.

My 1Z doesn't like the 4th gear when driving in the city.
As I said, shake and rattle.

I usually shift around 2100 RPM.

So, I shift into 4th gear around 60 km/h.
and then around 75-80 in the 5th [grade/year].

best regards

Hmm...
It might also be related to the fact that I drove a Volvo 740 (not a BMW) for many years, equipped with an original VW light commercial diesel engine.
It gets tougher, as far as shaking and rattling are concerned.

Hello,

"No, Rudi, that has nothing to do with the tractor. I agree with you; I also drive my 1Z (Rudi has the same model) in fourth gear through town (50-55 km/h, even with cruise control). You don't feel any shaking! I even do this when I have my apartment trailer attached, but even the slightest incline then causes instability in the combination."
BUT... my brother's Toledo (model 2000, 110 hp) doesn't seem to like it at all.


Best regards, Bertil.

Hello!

My 1Z starts up without any problems, although it makes a bit of a rumbling noise (possibly related to the water pump or wiring, as I've read somewhere), and runs smoothly at 50 km/h in fourth gear.
1Z - 202,000 KM.

Best regards, D.

Hi,

'Same here, I can easily maintain 50 km/h in fourth gear. It also works smoothly in fifth gear, although you shouldn't try to increase the speed too much, as it will start to jerk. However, fifth gear is also excellent for cruising.'

Best regards, Thorsten.

Hello, sorry for writing again, but how did you get rid of that rumbling noise? Did you simply loosen and retighten the engine mounts? I'm currently dealing with a very similar problem with my ALH engine and I'm not sure where to start. Best regards, Bernd.

Hi Bernd,
I also recently started using a clarifying shampoo on my 1Z.
- New hydraulic mount installed (the old one was dry and felt similarly tight when manually adjusted, just like the new one).
- New carrier with thermal insulation plate for hydrostatic bearings.
- 'Sponge reservoir' (front center) replaced (the reservoir, with its motor, was approximately 1 cm loose between the two buffer supports).

The car is noticeably quieter, especially when parked and idling.
What's still missing is the freewheeling pulley.

Best regards, Rudi.