Tapping Sound Coming From Engine Bay - Can Anyone Give Suggestions?

[tomclewes]

Hi
Car: VW Golf 2002 Mk4 1.4 Match model.

I recently brought a car from a dealer in Frome to later find a distinct tapping sound coming from the engine. This tapping sound increases as the revs increase, it basically does not sound healthy. Took it to VW for a quick listen and an independent garage and they both said it needs repairing.

VW suggested "bottom end bearings" and the independent garage suggested "tappets".

Below is a similar clip of the sound I am hearing:
http://www.youtube.com/watch?v=UIf5eGsHGTo


The car has oil, athough i doubt it was regulary topped up.

I have taken it back to the person i brought it off and said I want it fixed, which he agreed to do with his mechanic. His mechanic has said that it is coming from the bottom end shells as he currently has the engine stripped? He said that they are worn out and the copper layer is showing which is giving the tapping sound. He also told me it wouldn't neccesary cure the problem, it could quieten it, or even make it louder.


Mechanic told me that he plans to replace all the shells, and that there is no wear around where this problem resides.

Would you say this is a temporary fix or will it last a while? Only reason I ask is because I only just bought the car (hoping to sell in October when I can afford a higher engine), and if its a temp fix I will be demanding a full refund from the car dealer I bought it from under the sales of goods act which entitles me to a refund in the first 6 months.

Im a little wary as its the person who sold it to me's personal mechanic so he might of just said "just make up any horse crap"

My main question is are the bottom end shells prone to tapping? and how much are we looking for an official VW part as he said he could source some from "a mate that works with race cars"

Any suggestions or help are kindly appreciated, thank you

[MagicRat]

That noise on the video is most likely looseness in the valve train, such as an improperly adjusted valve, damaged lifter etc. since its a sharp rapping sound that was RPM dependent.

Problems with the bearing shells produce a deeper clunk or thump sound, lower down in the engine. Often such a noise is load dependent and gets louder and quieter depending on engine load.

[vgames33]

Sounds like a valvetrain noise.

If the copper is showing in the main bearings the engine is due for a rebuild.

[tomj76]

Valve train noises are loud above the engine and low end (crank & rod) noises are loud under the engine. It often helps to use a engine stethoscope and/or rubber hose to isolate the source of the noise.

Sometimes you can deduce the noise is a valve if you remember that the camshaft turns at 1/2 the rate of the crankshaft. Since 600 rpm = 10 rotations per second, the camshaft is turning at only 5 rotations per second. If there are five taps occurring in one second, then it might be a valve or lifter. However, each piston is only firing once every two rotations of the crankshaft, so you a low end knock that is only occurring on the power stroke would also have the same frequency.