1.9 TDI ATD: Engine Noise When Starting

Hello,

I'm still fighting – for the past 30,000 kilometers – against a persistent rattling noise when starting off... it sounds like a loose underbody panel that's rattling against the oil pan.

It only happens when starting to move, and very faintly when coasting in neutral at a very low speed, like the last few kilometers per hour before coming to a stop at a traffic light.

It gets worse when the climate control system is also running.


So far, I have checked, removed, and operated it without any issues or hazards.

- Hood liner
- Engine cover
- Underbody protection.
- Side underbody protection.
- Front bumper removed.
- Radiator mounting points replaced on both sides.
- Air ducts extended towards the wheel arch.
- Wheel wells removed/extended.
- The air intake duct in the engine compartment was lined with foam for testing purposes.
- All containers in the engine compartment were checked for rattles (coolant reservoir, windshield washer fluid, power steering fluid, etc.).
- The motor support at the bottom (the "bone" connecting the lower part of the engine block to the axle) was replaced because one of the hydraulic bearings had leaked, so it was going to be replaced anyway.
- Exhaust system from front to back.
- Driveshafts and their joints (both inner joints replaced due to play).
- Hood rattle (also rattles even with the hood open).
- Water tank cover removed.


You see, I've already been able to rule out "a little bit" of things.


Today, it was rattling again quite noticeably. I tested it, and the rattling sound was even present at a slightly elevated idle speed today. It's definitely coming from somewhere on the belt drive side, either directly from the engine or its mounting.

Der Riemenspanner-Zeiger tänzelt leicht, ca. 5mm hin und her - könnte es der Riemenspanner sein? Aber warum ists dann bei laufender Klima lauter? MSure, here's the translation:

"How much does it weigh?"

Furthermore, I noticed the right engine mount, which appears to be somewhat "compressed." I can't detect any other signs of defective engine mounts (such as cracking, a wobbly engine, excessive vibration, etc.). The only thing I've observed is that the car makes quite a "rumbling" noise when accelerating, but this is normal for the ATD compared to my previous ASV engine, thanks to the swirl injector technology.


Do you have any ideas? This clattering is really starting to get annoying.


I've attached some pictures of the bearing. Is that the right-hand bearing directly next to the timing belt drive? If you think a bearing could make such noises, then I would replace it. Hopefully, you can see that the bearing is deformed – the lettering on the rubber (which isn't very clear in the picture) is also distorted because of this.

I just want to avoid replacing parts unnecessarily. What I've already taken apart only cost me time and no money, aside from the worn-out defective parts I actually discovered in the process, like the A-arm ball joints, but that's not a big deal. The main thing is that I don't want to spend 50€ on the bearing if it doesn't actually solve the problem.


Greetings.
George.

Octavia_4x4 wrote:

Today, it was rattling again quite strongly, so I tested it, and the rattling noise even came from the slightly elevated idle speed today. It definitely originates from somewhere on the belt drive side, either from the engine or its mounting. The belt tensioner indicator is moving slightly, about 5mm back and forth - could it be the belt tensioner? But why is it louder when the air conditioning is running? More load?

Then just take the belt off and drive a bit. That way you'll already know if you're on the right track.

Could the ZMS possibly get involved?

No. The ZMS is already checked. Removing the belt without any tools is currently problematic.

Hey, we're also experiencing some jerking when starting our ATD, and I'm blaming the clutch. That's it. Uh, if the belt tensioner is slipping, the alternator is under a lot of stress, or the freewheel mechanism might not be working properly.

The clutch was replaced at 30,000 km because it was slipping badly.

The belt tensioner doesn't strike; instead, the visible lever at the top moves back and forth by about 5 mm.

I really don't like the wet and slightly collapsed rubber bushing on the engine mount.


Also, it's also mysterious: Sometimes the problem is there, sometimes not. And it definitely can't be the timing chain tensioner, because the noise comes from the right side of the engine block.

Hey, supposedly there's nothing that doesn't exist, but these engine mounts are actually not a big problem. As original new parts, they're also not cheap: mount left costs €74, mount right costs €75, and the lower support costs €49.
Exhaust pipe flexible section - check if it's okay? Timing belt and tensioner - are they okay? Remove the cover and visually inspect, also with the engine running.

Here's something quite simple: Could the exhaust system be loose somewhere? That usually makes a knocking sound, though. The metallic rattling could also potentially be caused by heat shields (often made of aluminum with VAG vehicles, right?). The durability of the snap-fit fasteners is often a matter of luck with other manufacturers as well; sometimes they hold, and sometimes they don't. What's interesting about these "heat shield" panels is that they are quite susceptible to resonance, meaning they react to specific vibration frequencies and only start vibrating at those frequencies. So, if it's not something related to the engine, then these panels might be worth a look. If they are somewhat sturdy (and not just embossed foil), you can insert a wooden wedge behind them to pre-tension them. Maybe that's where the noise is coming from!

RedR32 wrote:

Hey, it's true that there's nothing that doesn't exist, but these engine mounts are actually not a big problem. As original new parts, they're also not cheap: mount right 74€, mount left 75€, lower support 49€. Exhaust pipe flex section, is it okay? Timing belt and tensioner, are they okay? Remove the cover and then visually inspect, even with the engine running

.

Well, at EK (presumably a parts store), the MEYLE bearing for the right side costs around €35, which isn't too bad.


Exhaust system including the flexible section is fine. Timing belt visually inspected and appears to be okay, but I need to take a closer look at it.

It's just strange that this noise isn't getting worse, but remains constant. If it were the tensioner roller, I would have probably had to replace it by now after 30,000 km.

Hey,

Quote:

What I have expanded so far has only cost me time and not money.

Okay, then disassemble it and check for cracks .

Well, regarding the engine mount, I'm relying on help from a workshop because I don't have an engine support beam myself , but I think it will be the most sensible approach.

Hanging beams?! How about using wood and a few jacks, combined with some common sense, which you clearly have plenty of?

Have you checked all the mounting points and supports for the exhaust system?

Is the monolith possibly loose inside the catalytic converter housing?

No, I'm going to a friend's workshop, something like that is too risky for me...


The mounting points are definitely all fine, and there's no rattling when you tap on it.


It definitely comes from the right side, near the timing belt.

if of interest...

"I welded this together to make it easier to change the rear axle. It's made from simple 40mm square tubing. The two sliding ends are made from 35mm square tubing. I got the threaded rods, chains, and hooks at the hardware store. The supports for the body are made from a cut-open oxygen hose..."


And my daughter painted it blue.

Best regards, Holger.

Octavia_4x4 wrote:

... because I don't have a motor dependency bar myself...

Buy one!

http://www.fixversand.de/product_info.php?products_id=4092

It doesn't cost a fortune, but it's priceless!

Wow, that DIY project looks really good.

Okay, I don't do anything myself regarding the timing belt. Therefore, I need that beam exactly once. And since I'll be in Bayreuth this week anyway, I can have my acquaintance take care of it.


What's even more mysterious is that for the past few days, he's been experiencing a noise again that occurred last winter: extreme whistling/whooshing sounds coming from the charge air cooler system. It's definitely not solely dependent on engine speed, but rather on load.

Accelerate gently and steadily >> increasing noise; abruptly release the accelerator >> noise disappears.

The charge air path is completely sealed from front to back, the coolant is also fine, there's no oil mist anywhere, no soot, and no increased fuel consumption.

When the engine is warm, it's almost gone... the only likely culprit remains the EGR valve, which seems to be stuck open... and yes, I'm finally going to remove it and inspect it. Whether I'll block it or not is my little secret *wink*.


"EDIT: Just thinking about it: two weeks ago, when I was accelerating, there was a jerk followed by the car going into limp mode. The error message was 'Control difference boost pressure control - exceeded limit'... It never came back after I cleared the error."