Chain Rattle and Oil Check Valve

B6/7 S4/RS4
#1

Very interesting thread on AZ regarding chain rattle, and the potential role of the oil check valves.

http://www.audizine.com/forum/showthread.php/587325-Warm-start-rattle-solved-on-my-car!

So if the hypothesis is correct, a the oil check valve fails open, leading to rattle and excessive wear during start-up (until the oil is fully circulating). At first blush, I like the hypothesis. It also seems consistent with the folks that used Accusump to fix chain rattle (here: http://www.audizine.com/forum/showthread.php/484653-The-solution-to-chain-rattle?highlight=oil+buffer)

Interested in other’s thoughts. If the hypothesis holds water, I would be very interested in comparing how the RS4 handles oil check valves; i.e., is this a common failure mode, or just the S4 4.2L?

#2

A friend of mine wants me to try this repair on his car. He has been getting warm start up rattle. The plan is to take some video with my gopro before and after to see if there is any noticeable change.

#3

Use two or three sources of recording. Gopro is shit for sound
Maybe get an xtrernal Mic you can put in the enginr bay if you do use a gopro. Audiotechnica makes a grrat one for 20 bucks with a 20 foot cord. See gopro thread for deets

#4

How many miles on the car? The timing stuff should be serviced at 75k or so anyway.

Also realize that rattle is only a side affect of worn timing components. It happens but it does t change the fact that the nylon guides are brittle, and the adjusters are worn.

#5

It’s pretty amazing that this kind of information is basically just coming to light considering these cars have been around for over 10 years now

#6

This is going to be done on my car, which just touched 86k. I get cold start up rattle after about 7+ days of it sitting, get warm rattle about 25% of the time when restarting the car between 0 and mins after turning off.

Parts have been ordered and I’ll be working w/ Jimmy on this next week most likely.

#7

Tonight, I was looking through my Bentley Software for more information about these valves and I saw it mentioned: “Note: If irregular valve noise occurs repeatedly during short journeys and disappears after extended driving, the oil check valves must be replaced.”

So it looks like Audi knew all along about this issue but nobody apparently went searching through the factory repair manual information to find this stuff out.

That got me thinking about the RS4s and other engines.
3.0 V6 used a very similar system with two oil check valves and a oil spray nozzle. The 3.0s had lifter and camshaft problems early on.
3.2 FSI V6 has two oil check valves and a oil separator. The 3.2 FSI V6s had camshaft adjuster problems just like our engines early on.
RS4 4.2 FSI V8 has one oil check valve for both heads and a oil spray nozzle. I haven’t heard of any timing chain issues with the RS4s other than maybe RSGoose but it didn’t get fully diagnosed and solved to my knowledge.

Very interesting.

[QUOTE=p3u;9584406]Directly below the upper check valve is the oil jet btw as seen here.

http://i661.photobucket.com/albums/uu336/p3u/20140320_194632_zpswrplu6g5.jpg
[/quote]
The 3.0 V6s use a similar system and the oil jet valve is for the piston spray jets. I wonder if that valve is the reason that so many of these engines have scored cylinder walls. Maybe it gets clogged or stuck and then the pistons and rings get too hot causing them to swell and damage the cylinder walls.

#8

Good info Jimmy. Between your hypothesis about the passage way being stuck or clogged and the fact that the pre-cats are so damn close to the block, I bet there is a decent percentage of engines with scoring because of these to items.