Rb20det, Top End Rattle/clatter ?

[floody]

My RB20 has developed a rather nasty, harsh, rhythmic sounding rattle. Its a lot like a bad lifter sound but its concentrated and sharper, louder.

It happens from 2500rpm+ but stays pretty constant right to high revs. Oil pressure is fine.

It disappears with load, but is always evident on light throttle/free revving anywhere over 2500rpm, and sometimes on decel as you close the throttle.

Thicker oil seemed to move the noise up in the rev range a little without changing its pitch or volume.

It does sound a bit more randomly "clattery" on sustained light throttle, but in general its a rhythmic, constant noise until you gas it.

Noise is definitely concentrated in the top end.

Edited January 6, 2008 by floody

[floody]

Ok, I'm coming to the conclusion its in the bottom end, but that doesn't explain why its most apparent only on light load.

Also, would it be likely a bottom end rattle would set off the rich & retard functions of the ECU via the knock sensor? I note if I load the car up and launch off the line under load, hence no rattling, it pulls hard and clean through the revs, however if I walk off the line, move slowly up through the revs (and can audibly hear the rattle) then stab the throttle it overfuels and misses badly, feels to me like its very rich, very retarded.

I know its not an RB26, but maybe someone will have some ideas.

Edited December 19, 2007 by floody

[Roy]

Really, best bet is take it to trusted mechanic. Trying to diagnose noises over the internet is near impossible Good luck with it

[floody]

Really, best bet is take it to trusted mechanic. Trying to diagnose noises over the internet is near impossible Good luck with it

Oh I agree, about as easy as giving a haircut over the phone. I was hoping someone might think that my account was a bit similar to their experience. Trusted mechanic...I wish Looks like I'll have to skin some more knuckles and rip it to bits.

[TeeJay1600]

Mine had a rattle = shrunken piston.... they tuned the sound away so i just flog it now

[floody]

Update:

I've had both rocker covers off, turned it over on the starter and everything certainly looks to be working at that speed and everything rotates and reciprocates silently.

Tried different oil and flush to no avail.

The noise has become a bit more tinny but otherwise is just the same. Have done the long bar "microphone" thing and its definitely a top end noise.

Oil is clean, no particles etc that you wouldn't expect.

Must be getting on for 3500+ kms since I heard the noise so I am fairly confident its not a big end.