The most Mysterious challenging Engine Noise EVER!

[amare]

http://www.youtube.com/watch?v=phBsU20_63g

We’re dealing w/ a 1998 Audi A4 160,000 miles

The sound seems like it is coming from the Top BACK part of the motor.

If I remove the oil cap there is no difference in sound.

Replaced water pump and rollers – sound is the same

PLEASE HELP ! I’ve gone insane w/ this one !

The original thread w/ a few more details can be found here….

I’m at my wits end w/ this one…

http://www.audizine.com/forum/showthread.php/568051-The-most-Mysterious-and-challenging-Engine-Noise-Prob-I-ve-ever-seen-!!?p=9248581&posted=1#post9248581

Topic

[amare]

I have a little bit of an update. I listed the car for sale as a fixer upper and a guy showed up. I started it up and after just a few seconds he said it was a cam or crank bearing. He passed on the car and offer $400.

Another guy showed up. I fired the engine up for him and it only took him 5 seconds for him to tell me it was .. the main bearing.

I guess now we know…

[Nathan]

[quote=”grg8888″ post=80592]Hmm, that sounds like a whine at a multiple of the crankshaft speed. the rollers or bearings driven by the belt [/quote]

Someone already said that here.

don’t take this the wrong way but when you ask for advice online, make sure to read the entire comment.

[amare]

The rollers or bearings driven by the belt is just a little different from what these other 2 guys said..

They said the entire engine needed to be rebuilt due to the car not having oil pressure not just change the rollers which I took a fairly close look at.

Even if it was the same thing, it’s still new information as we’ve narrowed it down to the bearings I would imagine anyway.

[Nathan]

The timing belt or chain moves the crankshaft which in turn moves your connecting rods and camshafts. If a bearing is stuck, or out of spec with the cam lobe it is associated with, your going to get noise, on top of partsbthat will wear quickly. Now considering that car is almost pushing 20 years, this is to be expecred- especially if it hasn’t been maintained meticulously over its entire life.

Now the good news is you may not have to rebuild your entire engine. It sound to me like that shop is taking the easy way out. Oil pressure isn’t sent from the pump, pressure is built and maintained by the tolerances between any moving parts. The space between any moving parts “squishes” the oil, forcing it through thus creating pressure, and the vacuum created by valves and your pistons helps hold and regulate this pressure.

Now if your handy,, have a service manual, and a set of digital calipers you can measure each part in that engine, find what is out of spec/ worn and replace it. Compare your measurements to what Audi engineered and states is acceptable. That will solve your problem of pressure and noise. It will be 90% cheaper on top of it. Measure cam lobes, crank lobes, pistons, connecting rods & bearings, journals, lifters, valves, main bearings, check the cylinder bore with a bore gauge.. Etc..

Id start with the top end and replace what’s out of spec there, put it back together, check for issues (pressure, noise) and work my way down

[amare]

Well I like to think I’m handy but this would be a first for me.. What type of Service Manual or DIY could I find that explained getting to all of those parts?

[Nathan]

You could go onto Amazon or eBay and find a service manual.

I would gladly list them for you here, but I need to know if you have the Quatro A4 or the ‘regular’ A4, and I need the engine size as well… (is it a I4 1.8L Turbo or the V6 2.8L AHA?

[Nathan]

I should also add that if you’ve never taken off a cylinder head then I would strongly suggest that you have help from someone that has a least a small amount of experience with this.

[Author]

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