Crazy Noise After Rebuild... Help! (25Neo)

[Guishnu]

Howdy All,

I'm literally racking my brains on this one and I wanted to reach out and see if anybody had any ideas.

I fitted RB26 throttle bodies/plenum to my RB25NEO. Started it up, it was fine appart from head gasket failure. So removed the engine, did the head gasket. Put it all back together and now it starts and runs nicely but has this really bloody annoying whine!!

- It's coming from underneath the back/middle of the plenum.

- It doesn't appear to be coming from any injector (disconnected each cylinder and noise doesn't go away)

- It's there irrespective of fuel pressure

- It's there irrespective of whether the plenum is on or off (im running map sensor, so will run without plenum fitted)

- It's there if I remove the balance box/aac value and bipass the balance pipe

- I have swapped out the throttle bodies for another set. Still there.

- If you move the steering wheel to put load on the PAS pump, no change in volume or tone

- If you pump the brake no change in volume or tone

- It's there if you press the clutch

- It's there if you put it in gear

- It disappears if you rev cylinders 5&6.

- It decreases but is still audable if you rev cylinders 1&2 or 3&4

- If you rev the car with the plenum on, it goes

See the two video's below

Any ideas??

[r31 25t]

Gasket between the adaptor plate and cylinder head on 5&6 is where i'd be looking. You've done some good testing there.

[WMDC35]

have you tried spaying ether around the gasket area with it running? that should tell you if there's a leak

[SargeRX8]

Sounds like its coming from the 4/5/6 region of the motor. Is it definitely a mechanical sound(caused by a gasket) because that video sure does a good job of making it sound like electrical noise.

[Ben C34]

What do you mean by started up and was fine, apart from head gasket failure? Did the head gasket just somehow fail while you put on a new inlet? did it make that noise before the head gasket was changed?

[Guishnu]

The coolant was full of gunk, which I can only presume was something similar to radweld. I dropped the coolant, did the work on the car, started it up and the engine was mixing oil/water. I can only presume that the chap who sold me the car knew about it and threw in the headstop/radweld to get shot of it. The plugs were loose in the engine too. Bit of a mess.

Anyway - I seem to have isolated the problem. The adaptor plate was leaking air through cyl 5., causing high idle and the stupid sound (I hope) The inlet port on number 5 was full of hylomar sealant, where as all others were clean. I'm in the process of cleaning everything up, then i'll reassemble.

Fingers crossed and thanks for your help.

Chris

[GTSBoy]

Look for studs that have pulled threads out of the head at #5, just in case.