Very odd sound from cam or head, any ideas?

[ChrisCheezer]

R32 GTR 52,000 miles, stock motor.

new timing belt and water pump 5,000 miles ago.

The engine is making a very odd sound from the head, right under the oil cap.
Sounds exactly like a squeaking belt. ( humming/squeak, on and off only at warm idle)
its not loud, a bit quieter then the injector ticking. if throttle is increased ANY bit the sounds goes away.
used a stethoscope and its 100% being generated from the head directly under the oil cap.
before i pull the valve cover off and lift that cam cap any ideas? or recommendations?

[Skym]

Sometimes if sound comes from front of engine, it can be that the timing belt is overtightened.

Did you change the idler, tensioner bearings + mounting bolts (known to snap due to being weakened by lots of hot, cold cycles) at the same time???

[ChrisCheezer]

i thought it was coming from timing at first.. but the tensioner is quiet, and the pulleys are quiet. and sounds usually change or get louder w/ increasing rpm's... if its a pulley.
with a stethoscope it sounds like a cam cap under the oil fill, the sound disappears with the slightest increase of rpm ( ANY increase at all )

all the parts are new, but i didn't change the bolts..

[Skym]

Any oil leaks through intake cam oil seal (common problem with RB engine when they get older)???

[ChrisCheezer]

looks dry... ill have to really inspect it tomorrow.
humm.. that seal could cause that sound right

thank you

[Skym]

It's recommended to change crank (front and rear of engine), cam oilseals. I had the front intake, exhaust cam, crank oilseals done on my engine at the same time as timing belt, waterpump, tensioner, idler bearings. Had previously done mounting bolts when cambelt was done a while ago, so didn't need to do them.

[ChrisCheezer]

It's recommended to change crank (front and rear of engine), cam oilseals. I had the front intake, exhaust cam, crank oilseals done on my engine at the same time as timing belt, waterpump, tensioner, idler bearings. Had previously done mounting bolts when cambelt was done a while ago, so didn't need to do them.

were you experiencing a similar problem as me?

[Skym]

No. Preventive maintenance.

When I had a squeaky sound from top of engine during startup, etc, was oilfilter related. New oilfilter has a antidrain back valve (oil doesn't drain back to sump from oilfilter when engine is turned off), flows better, so don't hear a squeaking sound during startup anymore. Also top of engine is alot quieter when warming up.

I use this brand of oilfilter -

http://www.rycofilters.com.au/products/oil

Most use standard Nissan oilfilter that I think has the same anti drainback valve.

[ChrisCheezer]

humm... my car is equipped with a HKS oil cooler and relocation.
start up is perfectly quiet. the sound is only audible when its fully warmed.
using Mobil1 15 50 and a unknown filter.

the plot thickens..

any other ideas?... anyone

[Skym]

When engine is fully warm, thermostat on oilcooler sandwich plate (on shortblock) opens. Did you disconnect CAS plug (sensor on front of exhaust cam) and crank engine to prime the oilcooler core with oil when fitting oilcooler (I think is done when oil is up to temperature, as themostat opens)??? It could be the oil level is too low causing engine noise problems at idle and when you rev engine, oilpump moves more oil, so sound stops.

Similar with cooling system, did you remove bleed bolt and bleed cooling system of air while refilling with water, coolant mix and slightly overfill over max mark on overflow bottle??? Sometimes can be noisy waterpump.

Other area's that make similar sounds -

Auxilary belts
Bearings on Auxilary's (especially powersteering pump)
Low fluid level in powersteering resouvoir

Sometimes weird sounds sound like they are coming from engine, but they aren't.

[ChrisCheezer]

water pump is new, and dead quiet, after probing the whole motor the only place you can hear the sound through the scope is at the oil fill part of the valve cover..
Its something under there... i changed the oil about 300 miles ago... humm...
Ill check it out tomorrow and report back, as this one boggles my mind too

[BenC]

Yeah I would just lay down some newspaper, pull off the valve covers and pinpoint the sound. Maybe your orifice is plugged, restricting oil flow and resulting in squeaky valve train? Either way I would pull them off and figure out whats going on. Let us know how it goes

[ChrisCheezer]

Yeah I would just lay down some newspaper, pull off the valve covers and pinpoint the sound. Maybe your orifice is plugged, restricting oil flow and resulting in squeaky valve train? Either way I would pull them off and figure out whats going on. Let us know how it goes

I'm an Sr20 guy so the Rb26 is very new to me. So please don't hesitate to enlighten me of this motors operations.

If an oil galley was plugged the noise would be audible all the time, not just after warm up. If anything it would be more apparent when cold... no?
-start up/warm up is perfectly silent, after 20 min of driving the squeaking comes with out warning.

[beacher1B0]

Ben has u going in the right direction.
Do you have the RB26 engine manual? It could help!
If u dont, pm me your email and Ill send it to you.
Can you post up your oil pressure at each stage of start up -> squeek(if u have aftermarket guage), maybe when fully warm and idle drops down your head isnt seeing enough oil, but as rpm goes up so does the pressure.(that doesnt sound like your problem as u state any Rpm movement and its quiet). On start up you should get between 2-3 bar oil pressure, at idle when warmed 1.5-2 bar(These are just near examples not actual Nissan specs). If your alot lower your in trouble.
Is it possible the end of the cam has got some wear on it(either from age or overtightening belt when doing T-Belt). Oil galley could just have some carbon buildup in it restricting flow or maybe but unlikely your oil pump is on its way out.
If u take the oil cap off while running does it get any louder, how about dripping some oil down in there while its running(just a little as u dont want to go over the fill line on your dipstick). Could it be the type of oil you are using? Too thick or thin? Whatever it is, get in there and play around, there isnt to much that can go wrong as long as you dont pull your valvetrain apart. Since your an Sr guy you should be capable.
I could be corrected on anything I said above by one of our more knowledgable members. These are just some ideas.
Mike.

[ChrisCheezer]

OK update... basically eliminated possibilities
-cold start the oil pressure is between 6 and 8
-warming up around 4, finally settling slightly above 2 after 10 min.

shortly after (5min) our squeak starts sounding... so here what i did next.
-Checked oil level when hot in case the oil cooler was interfering when its thermostat opened, FULL.
-opened oil cap and shot the cam with oil no change.
-then i though, how could i lower oil pressure on my own see if it gets worse; so i lowered the idle almost the point of stalling, ( oil pressure dropped to 1.5) !!!the sound went away!!!
only at 900rpm's the sound is audible any lower or higher it goes away...
wow.. I'm stumped