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CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

So a few guys on the 914 boards have mixed opinions. But my car has developed "a noise" that worries the shit out of me.

At first, it sounded like an odd rattle. On my way home on decel the car made this odd rattle at about 2300rpms.

As I went "oh crap" I tried to reproduce it. It didn't make the noise. I pushed in the clutch and the rpms dropped, and again at 2300rpms the noise came back. It happens for a VERY brief moment.

At a dead stop, i was able to reproduce it. Car in neutral, rev engine and it would make it. Very briefly. It has significantly gotten worse and worse. I have no fricking clue what it is.

Symptoms are as follows:

- Makes a noticeable whining noise upon decel
- Approximately 2000-2300rpms it develops a significant rattle metal to metal noise, almost like you miss a gear but louder, more rattly.
- The car operates the same, it does not seem to have any loss of power
- The sound is not rpm varying, the sound does not change
- It can be reproduced upon decel or by pushing in the clutch and letting the rpms drop
- It can SOMETIMES be reproduced at a stop but rarely.

Ideas? Some say "that's your throwout bearing" others say it's my transmission.
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS

avaconirl · Joined: 25 Dec 2009 Posts: 48 Location: Ireland

Check the tin wear. If you can reproduce it in the garage try to pin point it with a stetiscope, if you dont have one try the old trick of using a screwdriver to your ear and to the engine and try to narrow down the problem. The other place may be the exhaust baffiles on the way out.

Best o luck.

CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

avaconirl · Joined: 25 Dec 2009 Posts: 48 Location: Ireland

When you sit in the drivers seat you sometimes feel the vibration. Any chance you can have a chassis problem or engine mounting prob.

CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

Well, I suppose it's entirely plausible. I guess what baffles me is how I could have a metal to metal grinding type noise. It's like a vibrating metal to metal rattling, almost like a bearing type noise.
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS

931Owner · Joined: 14 Feb 2009 Posts: 352 Location: Chicago NW Suburbs

Wish I could help. Maybe next time though.

I just decided not to buy a 73 914 with a seized 2.0L which I just saw. It had dual webers as well which was for $1,800 but a bit too steep for my liking!
_________________
1980 Turbo
-too many cars and too many motobikes

TJC · Posted: Sat Jul 10, 2010 10:56 am Post subject:

Given, that you say you can or discover the following:
Only feel the vibration in the driver's seat,
It reproduces the sound even when the car is at rest,
Makes the sound when the engine lid is down, but not up,
Happens only between 2000 to 2300 rpm,
Feel the back of the car vibrate,
Then my next questions would be:
Does it do this with the clutch pedal depressed, not depressed or both?
Since you have been working on this vehicle's exhaust system a lot lately, could there be something that may be loose from these repairs?
Did you check that the mesh and the PORSCHE letters on the engine lid were secured properly, and is the engine lid closing properly?
How severe is the vibration that you feel, and does it happen at rest as well as when you are driving the car?
Is the clutch properly adjusted?
Are the motor/transaxle mounts tight and and the rubber in them not deteriorated?
Are the shifter bushings in good shape, is there any slop in the shifter?
Are you certain that the noise/vibration is coming from the rear of the car?

Vibrations, noises and harmonics can play silly games. It's hard to diagnose a problem like this without actually being there, and I'm not trying to send you on a wild goose chase, but without more input it's hard to give you a definative answer. Depending on the severity of the noise/vibration I'd also tend to agree with the diagnosis of avaconirl that it could be in the engine tin, t-stat system etc. These areas are very prone to becoming loose on these cars and causing the problem you describe.
_________________
'95 BMW 318i/5 ..."Pearl"
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CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

!tom · Posted: Sat Jul 10, 2010 1:43 pm Post subject:

avaconirl · Joined: 25 Dec 2009 Posts: 48 Location: Ireland

To rule out would it be possible to listen with the screwdriver to the bell housing to hear if the clutch thrust bearing is knackered, it may save moving the engine to replace the bearing.

I will have to start reading these posts more carefully. You said that when the lid was open the noise stopped , is there no possibility that there is no loose tin on the lid, can you see if the bonding on the lid is intact, see if the hinges, springs or catch are ok also see if the realease cble is not rubbing somewhere.

I know that these may be have already been suggested but remember the last place you look is the place you will find the problem.

CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

Man I should just post my 914 stuff here. Lol i posted the same question on both forums and got way more replies on here. There were some good replies on there but so far no reports back as to info so who knows.

It is entirely possible it /could/ be loose tin. I will have to isolate it tomorrow night. Right now it's 12:15am and I'm pretty sure the bursch exhaust will piss off my neighbors but I was going to tackle it tonight. Tonight was a car club meet though so I said screw it.

Unless for some reason the sound is different with the lid up. It's entirely possible to be loose tin. But man it is a GODAWFUL noise that it makes, so that's some nasty tin.

I'm going to try to reproduce it at a standstill to see if it'll do it. I'll try it in gear, in neutral, clutch depressed, etc. It's hard to duplicate since it doesn't always do it. I'll also check for loose tin.
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS

Min · Posted: Sun Jul 11, 2010 8:46 am Post subject:

If your feeling it in your seat, its coming from behind you. Sounds like it could be harmonic for sure.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

CorsePerVita · Joined: 25 Jul 2008 Posts: 1992 Location: Redmond, Oregon

It was the stupid goddamn bursch exhaust. At 2300rpm the backfiring is vibrating the tail end of it and it is rattling the living holy hell out of the rear bumper. I FINALLY FINALLY reproduced it OUT of the car and caught it red handed!

Plagued me since I did the engine oil and exchanger seals. Never even occurred to me as it was in the same place it was. I didn't notice it was THAT tight.

Going to celebrate by driving it to work again tomorrow. The noise makes sense now.

Apparently when I turn hard left it bumped part of the bumper then holds itself up nice and tight. Once it does that it rattles the bumper and it flaps around like mad. Soon as I got the engine bay open i revved the engine since it made the sound, heard it from under the car but it was LOUD as hell.

Revved it and ran under the car, saw and heard it. Moved it and sure enough, sound was all gone.

"I'll be damned."

All that worry over something as simple as clearance on a bumper with the muffler. I can sleep at night now. I AM going to keep my appointment with german master tech though just so they can still scope everything out and flush the tranny for me - for the price they have, I can't turn it down, and hell, having a second pair of eyes to look it over and double check everything will be a good feeling.

I win this time!

_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

avaconirl · Joined: 25 Dec 2009 Posts: 48 Location: Ireland

Well done remember Patiance is a virtue