Engine Noise When Cold: What Could It Be?

Hi everyone,

I'm new here and have a rather urgent question.

First, some information!
I have a Golf 3 Variant, manufactured in 1997.
66 kW / 90 hp
Engine = AHU
Mileage: Approximately 137,000 km (all original, no modifications/chip tuning).
I bought the car used from a dealer about 9 months ago (119,000 km) and paid €7,800 for it. It still has some warranty , which is why I'm asking!

Now, let's move on to my demonstration.

When the temperature is below 10°C, my engine makes a very strange buzzing noise during the cold start phase.
The noise only occurs when the engine is idling. If I gently press the accelerator and the engine speed increases slightly, the humming sound immediately disappears.
Even though the engine is a bit warmer, starting at around 70°C, you can't hear anything anymore.

Was könnte das sein? Power steering pump?
Should I be worried about this, or is it okay as it is?

Since I'm a complete beginner, I would be very grateful for any advice or tips you can offer.
I couldn't find anything specific using the search function.

Hi,


Welcome to Diesel Mechanics.

Try it here: https://community.dieselschrauber.org/en/viewtopic.php?t=2149

I've had this problem three times with my 1996 1Z, but it might not be the same issue you're experiencing!

Hello,

I'm also new here and I'm having a similar problem.

My car: 1996 Passat, 1.9L, 90 horsepower, engine: 1Z, transmission: CTN.

After a cold start, a rattling noise can be heard at idle.
It occurs less frequently with a warm engine, and after repeated disengaging and engaging of the clutch.
If I press the accelerator a little, it goes away.

It must be something related to the clutch or the transmission, because when I disengage the clutch...
You only hear the normal engine noise.

The mechanic in my workshop said it's coming from the transmission.
After installing a used gearbox and a new clutch.
Is the noise still there?
The workshop believes the noise is coming from the transmission, but it's being caused by vibrations.
generated by the engine and could be resolved by increasing the idle speed.
Apparently, they can't do that with their VAG diagnostic tool.
Now I need to check if it can be done with VAG-COM...

The engine sounds normal, and it doesn't vibrate excessively either.
when I compare myself to other 1Zs.
I've been wondering if there might be a loose connection somewhere.
That's what causes it to vibrate.

Sorry, guys.

Now, I really need to ask again...
Unfortunately, I couldn't find anything relevant to my potential problem using the search function.

The humming or roaring sound will become louder as the outside temperature decreases.
This only happens when the engine is cold. Additionally, it only occurs when the engine is idling; if I give it even a little bit of gas, the roaring immediately disappears. However, the idle speed is within the normal range.

I couldn't pinpoint the exact location of the noise coming from the engine compartment, but it seems to be coming from the lower left area (when looking at the engine from above). (Possibly the alternator??)
You can also feel slight vibrations in the lower area of the passenger seat, which are likely caused by the humming/rumbling sound.

The clutch is also unlikely to be the problem, as the noise doesn't change when the clutch is engaged or disengaged.
I would describe the engine's performance as normal and unremarkable. The oil consumption is also unremarkable.

Therefore, I'm asking you experienced mechanics again:

- What could that be?
- Should I be worried about that?
- Could the humming/rumbling sound possibly be a sign of a more serious engine problem?


Thank you very much for your information!

Hi,
Could it also be a resonance from the exhaust system or heat shields?

I suspect the power steering pump is the problem, just like you do. Does the noise change when you steer? Or does it disappear completely?

If I understand correctly, this only happens when the engine/oil is cold?

Okay, I just checked the steering again, specifically the steering noise when the engine is cold.
The sound changes, if at all, only minimally.

I will check the exhaust or heat shield for any resonance issues again during daylight.

Is there enough oil in the power steering? I don't know why the noise should disappear when the engine is warm, as I've never driven it for so long with too little oil. }

Is there a belt that's partially slipping? Just try spraying a little brake cleaner (don't use too much, you don't want to set the car on fire, and be careful not to get any on your fingers) onto it while the engine is running and see if the noise changes.

Okay, one more thing: Try turning the heater's fan motor on and off as a test.

Best regards, Rainer.