Rattle noise for 1-2 seconds on cold start

[Johann]

Hey guys

I have a Audi A4, 2005 B7

When from a cold start I get this annoying startup rattle for 1-2 seconds then it’s gone. Engine is very quiet after this initial rattle. Car drives fine etc.

As I am aware this is a widespread problem but nobody has a definitive answer to solve this.

I have been driving like this for 2 years now.

We had the engine open the other day and there is no indication of wear or anything. Engine looks super clean.

Here is a link. My engine sounds precisely like it: https://www.youtube.com/watch?v=mBxoPelQC9w

Any help would be very much appreciated.

Thanks

Topic

[Mike]

I can definitively say the problem is that the oil used to keep the hydraulic lifters or a timing chain tensioner adjusted is bleeding out when it sits parked for long enough.

Whether that is happening because the lifters or a chain tensioner are worn out or because something like a oil filter drain-back check valve is not working or present in the installed filter, I’m afraid I can only speculate on. One thing really don’t know is what age that starts to happen, or if it happened with brand new cars still on the lot.

I’ve certainly heard the same thing from many modern VW/Audi engines and professionally I consider it normal and harmless, although I find their 4 cylinder engines to be absurdly noisy in general and find that startup noise and general engine noise unacceptable personally. All the ones I see are at least a few years used, near 100k on them, and are still noisy even after the startup rattle goes away. If a car of mine made noise like that, I’d go to almost any length to fix it because it isn’t “right” even though I do honestly believe its not harming anything. It seems like they all do it.

Getting back to the point, I would start by ensuring that a correct oil and filter combination is used. Absolutely synthetic oil, probably 0w40 weight, and a dealer or OEM aftermarket filter from a VW/Audi specialist (would probably also trust a Mobil1 filter). If that’s all in line, I might experiment with using a heavier oil that brings up the low number to a 5w40 or 10w40. I would be thinking about replacing lifters or chain tensioners next, but would certainly spend a lot of effort researching both the lubrication system’s technical data for any design flaws and forum people’s experiences with solving the problem first. If I came up with nothing new in that research, I’d probably shotgun chain tensioners in it and see what happens.

Replacing lifters would involve timing chain removal anyway and it would make sense to do them at the same time as new tensioner(s), but then if it fixed you wouldn’t know which one was bad unless there was something extremely obvious when you examine the parts in your hands. Also keep in mind that I don’t know if your FSI engine is an older style using a timing belt with the hydraulic tensioner in the head for the cam chain, or if it’s the newer style with all chains.

[dan]

agree with Fopeano on this one, it sounds like there is some excessive clearences in your valvetrain for a second, then it goes away, almost sounds like oil pressure isn’t keeping in the valvetrain when the car sets, so when you go to start it you get the rattles and ticks.

[Mike]

I wouldn’t say it’s an issue of excessive clearances.

Starting from 0 psi oil pressure in a static engine, it should be no surprise that it might take a moment or two for pressurized oil to get everywhere during a cold start. Perfectly normal. The sound disappears almost instantly. If the sound had continued after the engine was running, then we’d have good reason to speculate about excessive clearances.

[Jamie]

Its a more common issue than people really want to admit. Some people started using thicker oil, and some people switched to using only European oil, witch is expensive as hell.

[dan]

[quote=”Evil-i” post=146925]I wouldn’t say it’s an issue of excessive clearances.

Starting from 0 psi oil pressure in a static engine, it should be no surprise that it might take a moment or two for pressurized oil to get everywhere during a cold start. Perfectly normal. The sound disappears almost instantly. If the sound had continued after the engine was running, then we’d have good reason to speculate about excessive clearances.[/quote]

That is not exactly what i was trying to say, let me re word this…….. in some cases a engine has hydralic lifters, even over head cam engines have some hydralic lifter on some parts of the valvetrain that take up clearances between parts as they wear out so adjustments don’t need to be made too the valves, and also reduce underhood valvetrain noise…
If your engines valvetrain is the type of system that has hydralic lifters that take up clearances between parts, if there is no oil pressure up there well there will be excessive clearances between parts as a result, also oil film between parts also takes up clearances between parts so there isn’t metal to metal contact, so if there is no oil there now the parts tick and knock together.

[edward]

if you suspect that you have a lot of clearance like said up here just had a oil stabilizer during your oil change interval if you notice a difference that might be your issue if not you might have air in fuel another possible cause

[Author]

Replies