Engine knock - should I be worried?

[tssupremacy]

I just bought a 96 gtb which has done 139kms. It goes fairly well, but the engine has quite a distinct knock to it at cold idle and also on power. Ive owned 2 legacys before, and none sounded like this.

I've read that these GTBs have forged pistons and they slap around a bit. Has anyone else had experience with this? Is it something I should be worried about? :-[

On a side note, I also diagnosed an issue with my air flow meter and have just bought a replacement. I would think this was related though.

Cheers

[funkytown]

post a youtube clip of the noise. no one can gander what it is from your description as there are a range of healthy and unhealthy knocks it 'might' be.

welcome along - look forward to listening to your clip.

[Flat4]

If the sound goes away when its warmed up then it's probably piston slap, seems to be pretty common with GTBs

[rico]

Yeah mine is pretty loud these days with the cold weather.

As mentioned, I think as long as it gets quieter as it warms up its probably nothing to worry about?

Mine is loud as at startup and I can still notice it when taking off at lights etc even once warmed up but has been like that for over a year and still going strong so I'm just assuming its piston slap.

[Nick_96_RSB]

My RSB has some mean slap when cold, goes away once warmed though, has been there for at least the year and a half i've owned the car( its only done 3k more than yours), i just make sure its nice and warm before i give it a decent thrash, just make sure you change the oil every 5 - 10 thousand k, use decent oil, and warm it up properly before getting on boost

also the forged piston thing is a myth as far as i can tell from info on teh webz and very much doubt your faulty AFM has anything to do with the slap

Im going to pick up the missus soon, if its not raining cats n dogs when i go, ill try take a video of it so you can compare it to yours

[Skinon!]

Yep my bh5 slaps too randomly and seems to only do it on decel, but has stopped now haha... Car goes mint so i wouldnt worry about it unless it gets worse

[tssupremacy]

Thanks guys,

Ill get a youtube clip up when the rain stops... could be a while!

[Deforester]

I had a bg5 that used to slap real loud when cold. I remember looking at it before buying it, the guy selling it said something like "I'll start it up, dont worry about the horrible clunky noise, my mechanic reckons its common"

[calibre]

 Deforester said:

I had a bg5 that used to slap real loud when cold. I remember looking at it before buying it, the guy selling it said something like "I'll start it up, dont worry about the horrible clunky noise, my mechanic reckons its common"

and you still bought it!

[Deforester]

 calibre']

[quote name='Deforester said:

I had a bg5 that used to slap real loud when cold. I remember looking at it before buying it, the guy selling it said something like "I'll start it up, dont worry about the horrible clunky noise, my mechanic reckons its common"

/quote]

and you still bought it!

Lol yes I did, after a couple minutes running it all harmonized and ran nice and smooth. In retrospect I could have been in for all kinds of trouble!

[tssupremacy]

Righto Gents, here's the youtube clip.

Probably also unrelated, but took it for a drive to town today after replacing the AFM and it drove well. But on the way back, if I gave it some gas, it would splutter and hesitate. Also the heater has stopped working! Have I bought a Suby Lemon?

[subaru-mania]

Knock does sound more like piston slap rather than Beb , as it doesn't seem to be getting louder as the rpm increases , when if it was Beb it Normally gets louder and faster with the revs , personaly i keep clear of twin turbo subbies

[subi4snow]

Get a motorbike instead mate... ;D Oh Wait?

[Stoffa]

mine had a similar knock, turned out to be waterpump on its way out

[funkytown]

notice how that knock disappears when you rev it - this means its 99% not BEB. BEB gets worse with force applied to the crank.

you have slappy pistons or possibly a worn auxillary like waterpump.

I assume you've taken this from a cold start - can you repeat after a good 15mins driving and post plz.