hi folks, i'm new to the forum so be gentle! - after some advice. We have a 2007 (run out of the old shape fabia) 1.2 htp and it has recently developed a loud rattle form the top left of the engine (when looking under the bonnet form the front) on start up. It only does it for a second or two and only when cold but it sounds like satan beating the hell out a lump of metal....Now heres the rub - i changed the oil 4k ago but not being clued up on VAG engines i put in 10.40 semi synthetic as i thought ,  its the wifes car and she does little mileage and drives gently. 

Having just bought a passat and read up on the oils required for vag engines i will change it this weekend to the correct vw502 spec but worried i have permanently damaged something....

Help!!!

Mine originally ran 10w40 with no issues could it be the exhaust against the body?

Timing chain.

Timing chain.

Which if incorrect oils are used for a prolonged period of time can be damaged by them

I will be putting in the right oil this weekend and as it's only done 4k hopefully it will be ok... Cheers guys !

Mine originally ran 10w40 with no issues could it be the exhaust against the body?

It's a rattle rather than a knock from an exhaust and from the top left of the engine

The timing chain has only done 4k?

I'd be double checking bolts if so!

Take the oil cap off and get someone to start it for a second, see if it's any louder. The chain runs just beside the oil cap.

Seen a few posts recently of the tensions failing as well.

The car has done 35k but 4k with a cheap oil in- good Idea about removing oil cap. Are the tensioners hydraulic or spring activated?

Tensioner has spring and oil-feed. If the car does a lot of short journeys, oil quality may become very low even with low mileage. 4000 miles done in 2-mile chunks is far worse for the oil than 10000 miles done in 10-mile chunks.

Is it the 6-valve 54bhp version or the 12-valve 64bhp?  (Latter has an extra component in the breather system so theoretically less prone to oil degradation.)

It kinda does trips to work around 15 miles round trip. It's the 12v version. Hopefully all ok

Sorry to be the one to tell you, but poor quality oil won't make it sound how your describing. As said the tensioner relies on oil pressure.

When the car is first being started it has very little oil pressure from cranking speed, hence why you get a rattle until it starts up and idles giving it full oil pressure.

Now it's possible if its had a hard life with very poor servicing the chain may have suffered. The paper filters need to be changed regularly to keep oil pressure high.

A very bad loud rattle to you, might just sound like a worn timing chain to me. If the rattle goes away when it's started and idling maybe try an oil and oil filter change and see.

i know its had a gentle life and filter and oil changes every yr, i'll stick the proper oil in this weekend and see but would the timing chain be worn on such a low mileage motor? its only done 35k - i'll report back next week.....ta folks

No, that should be fine assuming as you say it's had an easy life and well maintained.

I changed my timing chain at around 60,000 as a precaution and nothing els. Was silent on start up also.

Whew! Appear to have got away with it. Engine now peachy smooth and no rattle.....

That's good to hear