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morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

ok.....so its a ROW S2 engine.

now fully serviced with new oil..new water pump and belts...valves adjusted to 0.20mm intake and 0.30mm exhaust.

oil pressure with cold engine is over 6-7 BAR at 1000 RPM(WUR) idle.
oil pressure with warm engine 2 BAR at 750 RPM idle.
oil pressure with hot traffic engine is 1 bar at 750 RPM idle.
oil pressure with hot engine at 3000 RPM is 4 BAR.

in any situation just touching the pedal and getting it over 1000 RPM gets the gauge to point at least 2 BAR.

driving the car is very very nice...it feels and is very powerfull and the engine sounds very healty and just eats the road.

However..if i open the hood and i listen to the engine rev and fall back from rev i can hear a most distrubing noise.
its a "gargle" that can be heard when the the engine falls back from rev. So when i rev it from the engine bay...when it falls back to 750 RPM...just there when it goes from ~1500 to 750 RPM i can hear a gargle wich has a higher frequency at ~1500 and drops in frequency with the engine rev. When the engine aproaches idle RPM the engine quiets down and the sound can be heard easly but the frequency of it decreses and as soon as the engine reaches idle speed the "gargle" dissapears.

now...what the #### is that ?

havent done a compression test yet but i dont think that its necesary....the spark plugs are BARE METAL CLEAN...the engine runs very smooth and at idle you can hear just a kitty purrrrrrrrrr.
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Nobbi · Joined: 24 Aug 2006 Posts: 1397 Location: Germany

Hey morghen,

afik the idle rpm should be 950 +. So get youre screwdriver and adjust it.

Nobbi

750.... my engine isnt running that low at all.........

johnathan1 · Joined: 08 Oct 2007 Posts: 308 Location: Downey, Ca

Sure you aren't just hearing your exhaust?
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Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

I'm with Jon, it sounds exhaust related. Loose baffle, perhaps? Manifold heat shield?

Does it make this sound when you rev up slowly from idle to 1500?

Can you locate the sound at all?

How are your engine mounts?

Everything else in you engine seems fine, so I don't think it's too much to worry about.

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morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

no...its probably not the exhaust as i recently removed it and welded it.

The "gargle" seems to come from inside the engine. but its very dificult to locate it as there are many resonances that misslead can you.

engine mouns are good condition. the heat shield for the engine mount does not exist

however it sounds like something internal to me

i did not try to gently rev it...will do that as soon as i get home !

i'll try to get some professional recording tools and get an accurate recording of the engine as nobody seems to know what that could be.
Some mechanics said it can be some problem with a piston. but nobody said what exactly.
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Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Nobbi · Joined: 24 Aug 2006 Posts: 1397 Location: Germany

just a possebility,

take off cam cover and check that oil-line thats installed on top of the valve timing. They are often found brocken and they can cause a irritating
noise.( The broken part itself)

Nobbi

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

checked that Nobbi..its like new.

i did not take the manifold out..just the flange coming out of the turbo.
i welded it and then smoothed the inside of it. did not tuch anything.

i'll try to get the recordings tomorow.
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joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

If you think you are hearing piston skirt slap, listen to the engine when it is cold and see if the noise changes. The parts havent expanded when they are cold. If the gargle is the same note all the time at that rpm regardless temp, it may not be your internals.
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Paul · Posted: Sat Nov 03, 2007 12:27 pm Post subject:

Grab a hunk of hose and use it to listen to the bypass valve in the intake side of the turbo.
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924guy · Posted: Sat Nov 03, 2007 9:51 pm Post subject:

air bubble in the coolant path causing cavitation noises.. long shot, but stranger things have happened with these cars ....
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dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

By chance have you opened up your exhaust? My 928 started doing the burble thing when I installed a rear muffler bypass. This is the result of the ignition retarding during deceleration so the after burn in the exhaust is more noticable. Another possibility is that the ignition has been retarded due to a vacuum leak or bad connection affecting the DITC.

Dennis
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morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

so its defenetly something hitting itself against another moving part.
I'm 70% sure its a tappet or a valve guide as when the engine is cold i can hear the noise more clearly and its coming from the cyl head not lower.

However the noise is NOT all the time present and as i said it can only be heard from the engine bay.

As a statistic: i reved the engine 5 times and only 2 or 3 times i could clearly hear that noise.

Also..on close inspection to the camshaft...there seems to be some sort of begining of wear to it...at least on the exhaust lobes wich are pointier. it looks like when you hammer a metal...but the wear is not big at all. The tappets look great...no sign of wear on them.
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RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

If you feel that this noise is originating up top rather than piston slop or gudgeon noise you may be on the right track with the tappet. Some years ago my engine developed what may have been a similar noise. Turned out to be a tappet that had by then broken in two horizontally, top and bottom half around the screw hole. Even had the cover off and checked the clearances previously and didnt find it. Must have started as a crack and opened up with use. Didnt find the problem until it had chewed out the tappet bore.

So if you suspect a tappet, may be time to pull the cam and examine each one, and the adjustment screws for unusual wear. Probably also be able to give the valve springs a basic push test too at the time.

Good luck whatever it may be. Hope its not your pistons!

Roger

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

After some more listening to the engine...and getting more opinions...i have this:

The fact that the noise comes from the top side...is just an echo inside the engine case...

1. The noise is louder and more audible when the engine is cold.(the DITC sets more spark advance when cold to obtain a higher idle)
2. The noise only comes on when the engine is droping from revs.
3. The ocasional "gargle" that i have been hearing under hard acceleration...seems very similar to the sound from under the hood.

All these translate into:

The only sound in an engine that meets the description that i have made is the sound made by the crankshaft bearings. So...yea...i hope no damage to the crankshaft.
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